82 380 SEL Overheating on Hill
 

My 1982 380 SEL is overheating. The wierd thing is that it only overheats when I push the engine going up a long steep hill to my home. Othewise the temp gauge hovers just under the 100 degrees level.

So while driving around the city, the engine temp is fine. But when I go up the mountain to my home, the temp rises and the car over heats.

I changed the thermometer this weekend and it didn't make a difference. I don't lose any fluid unless it over heats. I checked the fan and it is running when the engine is at running temp.

Any suggestions?

Many thanks for your help....

did you change the thermoSTAT? if so what temp stat are you running? how big is the hill?

if you are running too high a stat, you may not have enough reserve cooling capacity available when encountering a hill.

hovering just under 100 seems too high for a normal op temp.

also your radiator may be marginal, either plugged internally or externally.

tom w

MB Thermostat
 

Thanks T:

I bought the thermostat directly from our MB dealer. So I really don't know what temp it runs at. Sorry for calling it a thermometer....work term....

The hill is about 3 KM and runs to an elevation of 1200 ft.

So your theory might be correct and the coolant might be too hot at the bottom of the hill. I guess the engine runs pretty hard getting the beast up the hill and the coolant boils.

The radiator was changed by MB a few years ago, so I assume it must be a good one.

So your suggestion is to change the thermostat to one that runs cooler? I've read about running without a thermostat, what do you think?

It was a VERY difficult project to change the thermostat as one hose on the housing was really difficult to work with.....

How would I find out what temp the thermostat runs at?

Many thanks T! and everyone else....

You definitely don't want to run the engine without a thermostat. The temperature should be stamped on the thermostat. Call your local MB dealer and verify that the thermostat you bought is the correct one for your engine. Assuming it's the correct thermostat, is it installed correctly and is your cooling system filled with a 50/50 coolant mix? You may need a new cap for the expansion tank.

Correct Thermostat
 

Hi Fred:

Thanks for your post.

I am looking at the MB box the thermostat came in, and it doesn't say what temp it runs at. I don't want to take the thermostat out if I don't have to. I've also looked at the old MB thermostat I took out and it doesn't have the temp on it.

I'm pretty sure I installed the new thermostat correctly. The car runs fine until I encounter THE HILL! I refilled the fluid with new 50/50 coolant.

Good point about the cap for the expansion tank. When the fluid boils, the cap appears to be fine, because the fluid leaks from the small valve on the side of the expansion tank.

Any other suggestions?

Thanks again Fred.

100 is too high for normal running I think. Should be more like 85. Have you been using MB coolant? How often have you changed the coolant? Might want to try a bottle of Water Wetter. Although it is not designed to reduce normal operating temperatures, it may prevent the coolant from heating up as much as it does on the hills. Is your coolant level correct?

Len

Water Wetter?
 

Hi Len:

No, I didn't use MB coolant. Does it really make a difference?

What is water wetter? I've never heard of that? Do most automotive stores have this?

Yes, the coolant level is correct. Slightly low today as it boiled over and leaked a little last night when I drove up THE HILL!

Thanks Len...

At the risk of starting a holy war, I'll say that not having MB coolant in your '82 MB isn't your problem. I would ensure that the concentration of coolant is no more than 50%. These engines actually run cooler with < 50% coolant concentration. I run approx. 40% coolant - 60% water and live in a hot climate.

Water Wetter - visit their WEB site and you'll learn this product only helps when a VERY low % of coolant is used.

Ensure you have sufficient air flow; water flow.

Here's a pointer to an old thread that covers the overheating on a hill issue. In the end, the orig. poster solved the problem by replacing a worn out fan clutch.

http://www.peachparts.com/shopforum/showthread.php?t=102579&highlight=overheats+hills

Some believe that the fan clutch only serves to cool at lower speeds and at idle. Years ago I battled an overheating issue on another car. It only ran hot on the highway. I replaced everything there was to replace, then had a conversation with a veteran tech about the fan clutch. Sure enough, it turned out to be a tired fan clutch.

I'm not saying this is your problem. Just something else to consider.

Sounds about right.
 

Hi Mike:

Thanks for the link. I read the other thread and it sounds very similar. (Tried to do a search on the subject but didn't see this thread.)

Now a few questions:

1. How would I check to see that this could be the problem?
2. How big of a job is this? Is it a DIY or MB job?
3. Costs?

Hopefully, problem solved....

For me. it was a diyer job. I bought the 2 special tools used.

a. 8mm Stahlwille allen head socket - loosen fan clutch bolt.
b. foot long metal rod - hooks in back of clutch to prevent it from spinning in order to loosen bolt mentioned in a.

Doc is at the following WEB site. For your car, they show operational theory and not actual disassembly. You can fish around for the actual process looking at other models of 126 cars - cooling system - to get the process. It's covered in one of them - which I don't know.

http://mb.braingears.com

The tools may be obtained from Baum Tools -> baumtools.com

Brad, I'm unfamiliar with a valve on the side of the expansion tank ... it's probably the level sensor. It's important that your cooling system is leaktight, especially in your situation where you are taxing the cooling system with your steep hill. The cooling system is designed to be under pressure which increases the boiling point of the coolant. Since your cooling system leaks it cannot maintain pressure and the coolant is boiling off.

Hi Mike/Dr. Brad - not suggesting that recently filling the car up with non-MB fluid caused this problem. However, long term use of non-MB coolant and especially not changing the coolant on the prescribed schedule could lead to cooling system problems. Need to also make sure there isn't an air bubble in the system after the thermostat replacement. As to Water Wetter, my experience has been positive. My 240D used to creep up to 95+ or so during a hard hill climb and in stop and go traffic. After adding Water Wetter in conjunction with a cooling system service, my temp gauge is rock solid at about 85 now under all conditions. It's been that way now for at least ten years, although I do change the coolant every three years. Now, maybe the fact that the system was serviced at the time I added the Water Wetter comes into play, but I've heard similar stories from others too. Certainly I'd look at the coolant level, the concentration, the air flow, fan clutch, etc. There are lots of things that need to work right.

BTW, Water Wetter is available at most auto parts stores.

Len

Next Step
 

Okay...the next step:

- I will take the car out today and drive up the hill. According to the other thread, once the car gets really hot, I'll pull over, turn off the engine and check to see if the fan stops spinning after less than five rotations. I understand this will tell me if the fan clutch is worn.

- secondly, I may have to flush the cooling system. I trust this is quite simply to open the drain valves and then flush it with a hose and refill?

I'll report back in a couple of hours on the status of the clutch.

Wish me luck in getting back up the hill.

Brad.

Len - I hear ya.

Dr. Brad - You don't necessarily have to "go to the mountain" to test the fan clutch. If it's worn, it's worn and everyday driving will show this.

Do drive the car 'til it's good and warm, then pull over. Leave it idling. Pop the hood. Close front door - leave window down. Reach in and turn off car and quickly look fwd. to engine bay. Fan should not be spinning.

I find it helps to do this test with a second person sitting behind the wheel. Have then shut off the motor while you watch the fan blade. If the engine is fully warmed up, the fan should stop spinning as soon as the engine is shut off.

Will do it now
 

Hi Mike:

Ok...since I'm not working today, I'll drive the car around the block a couple of times and report back to you in 10 minutes.

Thanks for your assistance.

Brad.

OK..Report
 

Hi guys:

Ok. I took it off the mountain and drove back up the mountain. The temperature guage maintained at way less than 80 degrees as I coasted down the hill.

When I drove back up the hill, at about half way up <1 km, the guage hovered just above 80 degrees. I assume this is when the thermostat opened up fully. As I approached my house at about 1.5 km, the guage jumped to over 100 degrees and then dropped down to just above 80 degrees. (It's a cool morning here in Vancouver.) So, I couldn't get it to over heat today.

When I got home, I pulled into the garage, popped the hood and turned off the engine. The fan IMMEDIATELY stopped spinning when I turned off the engine.

So...I guess this means that the fan clutch is ok.

My next step may be to flush and refill the cooling system?

Any other suggestions?

Thanks so much for your help.

This is kind of like medicine.....consult that is...

Brad.

As the radiators on these cars get older the temps tend to rise a bit. They should run at 80C give or take a bit.

You should remove and clean the radiator, the finns are probably clogged with junk. If that doesn't do it replace it.

The overheating under heavy load is a clue that the radiator is marginal.

Cleaned
 

Ok...I'll check the front of the radiator and spray it down with some water to clean it.

Is there a proper way to clean the radiator on the outside?

Many thanks for everyone's help.

Yes, first you need to remove the radiator. Once it is out of the car you will be able to hold if up to a light and see what is clogging the fins. Hit it from behind with either an air compressor or gardon hose to dislodge that crap.

Check your AC condensor as well, those clog up too.

I see that someone earlier in the thread mentioned the pressure cap on the coolant reservoir. Did you change the cap? If so, what was the result? I ask this because I just attended to a few simple things in the cooling system of my 94 C280 in May, and I have found an improvement in how the car handles high heat load. I have always changed the coolant according to Mercedes specs, and always use the Mercedes coolant. But this time I changed every hose in the system (I don't trust 13 year old rubber) and had a new pressure cap installed. I've had the car for over 6 years, and have never changed the pressure cap. I have no reason to believe the previous owner changed it, either.

Now I'm not naive enough to think that changing the hoses has done anything for cooling system performance. But as I said, the car handles high heat load better now. It doesn't heat up like it used to when stuck in traffic on the highway, or when moving into city traffic after being on the highway for a while. I suspect that the cap was no longer providing its full pressure, which lowered the boiling point of the coolant, which then resulted in decreased system performance.

This might not be your whole problem. But it might be a contributing factor. I'd suggest replacing it and seeing what happens before you go pulling the radiator. I was very surprised at the measurable difference from this simple thing.

Cap
 

Hi J:

Many thanks for your suggestion. I know it gets a lot hotter in Toronto than in Vancouver.

I will swing by MB tomorrow and pick up a new cap and see how it affects my problem.

Things were pretty good today. It was about 20 degrees today and cloudy. The temp guage fluttered a bit. While driving for the first 10 minutes it hovered just less than 80 degrees, then spiked to above 100 degrees, then settled to just over 80 degrees. When I came to the hill, it stayed at just over 80 degrees, until I got three quarters the way up the hill (about 1.5 km) then it spiked to just over 100 degrees. It stayed there and didn't boil.

Any other suggestions before I consider pulling out the rad?

Many thanks again to everyone!

Couple of comments -
1. Sounds like good advice on troubleshooting through the clutched fan and into the radiator itself
2. I hope some day to see some independent data on Waterwetter - so far, all I can tell is that is a self licking snake oil ice cream cone - reduce the ratio of coolant to water and add water wetter and it will run cooler. It will also run cooler if you reduce the ratio of coolant to water and don't add water wetter, right?
3. I would think your V8 should take that hill with limited stress - after all, it's not Texas in the summer .... it should normally run a bit about the 80C mark
4. Could there be a blown head gasket that is setting up heat bubbles in the coolant that sweep through and cause the spiking?

Waterpump
 

Have you checked the condition of your waterpump, it could be that the pump is not functioning to its full potensial and when heavy load is put on the engine e.g. when going up a hill, the reduced flow of water is not sufficient to cool the engine down.

I will wage my 5c ont the waterpump, there is only a limited number of things that can llead to a over heating engine:
1. blocked inner radiator core
2. blocked outer core of radiator, air not getting by the fins.
3. none functioning thermostat
4. blown head gasket
5. water pump

In your case i wouls suggest cleaning the radiator, get a new cap, if this does not solve your problem, change the waterpump

Water Pump
 

What sorts of symptoms would I expect with a faulty water pump? The car appears to be just fine, and only recently started overheating with the hotter summer weather and only when climbing the hill.

In otherwords, would I see a heating problem with regular driving?

Thanks for your suggestion. I will be getting a new cap this morning on the way to the clinic.

Brad.

Usually with a bad water pump, you ought to see a little bit of coolant weeping from the water pump area.

Len

I have been on the sidelines watching this one.....

This seems like a classic case of a partially clogged radiator.....

it does not take much to pull a radiator and clean it good....

it might be just as easy to buy a new radiator...pretty cheap item..

I have a potential problem with my 380SE. While it does not overheat, it comes close (in my opinion). The gauge goes 3/4 of the way up (near or slightly over 100*C) in SLOW stop and go city driving. It may not be classified as overheating, but it goes higher than I would like for it to be. On the highway (at speeds over 55), it runs normal. I NEVER have seen or heard that auxiliary fan on. The ONLY time I ever hear the clutch fan is when I first leave of the morning (when the car is cool) and I can hear it ROAR until the car gets to about 40 MPH, then it quietens down. I never hear the fan again, no matter in engine temperature.

I guess I need to check.... 1. clutch fan, 2. aux. fan, 3. change coolant, 4. flush radiator. Oh, BTW, yes, it has the "no-no" green coolant.

Lots of Background Info
 

Well, went to MB yesterday to buy the new rad cap. Here's the scoop.

• the MB thermostat opens at 84 degrees celcius.
• I bought a new rad cap and put it on yesterday.
• the car is a 1982 380 SEL.
• I bought it from a friend's dad who had it serviced at MB for 25 years! (Incl. all oil changes)
• MB printed out the service history (39 pages.)
• aside for some other major MB service (tranny, timing chain, etc.) a new MB rad was put in at 190, 000 Km (present milage is 224 K)
• the parts guy I spoke with suggested all of the same things that have been mentioned in this thread. (Fan clutch, thermostat, he was doubtful about the cap, but it only costed me $12 CAD)

So, yesterday was pretty much the same as the day before. No heating problems while driving around the city. I didn't drive up the hill until late at night, (and it was quite cool last night) and although the temp did reach above 100 degrees, she didn't boil.

To recap...I've changed the thermostat, and now changed the rad cap...and still no noticable change. My main problem continues to be overheating when driving up a long steep hill.

I've checked the fan clutch, and the fluid mixture and it's very clean. The rad looks clean but I may try to leave it in and just spray it down today followed by air from a compressor.

Thanks to everyone for following this thread and assisting me with the problem. Where should I go from here? I love this car, but never had problems like this with my Toyotas!

Brad.

AUX Fan
 

I was out today trying to clean the outside of the radiator and noticed that there is a fan INFRONT of the radiator.

I've now looked at my manual and figured out this is called an Auxillary Fan.

When I checked the fan, as previously suggested, I checked the fan behind the radiator.

Anyways, the car was still warm...not hot...but warm...and I turned on the engine. The fan behind the radiator was spinning, but the one in front wasn't. Can someone tell me more about this Auxillary Fan? Is it clutched? I took a look in a Performance Products Catalog, and it shows an exploded diagram of the engine and cooling system. It looks like this is an electronic fan? Maybe its broken?

Any suggestions would be apprciated.

I think I'm getting closer to the problem.....

Thanks again to everyone....

Brad.

AUX Fan Info.
 

I've done a search and read another thread regarding Auxillary Fans.

They were talking about a different car, but I assume the principles are the same.

Can someone explain more about the fan systems to me and how I can determine if the front auxillary fan is broken. If so, it doesn't sound like its that difficult to replace.

Any help is greatly appreciated.

The electric fans are only really important if you are running the AC, other then that they almost never come on. On my SDL at least they don't kick on until 105C.

I'd say the viscus fan clutch is week, or your radiator is clogged. Overheating under heavy load is a classic radiator problem.

Thanks.
 

Thanks Hatterasguy. Would you still think that the radiator is the problem even though it was changed by MB 34,000 km ago?

I read on the other thread that the Aux Fan should be running the same time the main clutch fan runs. I guess this person was wrong?

Thanks. I guess I'll take your advice and flush the radiator this week.

This task is not the most simple of tasks.

When you remove the radiator from the vehicle, hold it up to the sun. If you see accumulated debris in the fins, it's your task to remove same. Water from a garden hose won't cut it. Compressed air won't cut it.

The solution is the use of a commercially available condenser cleaner in conjunction with compressed air. Careful use of a pressure washer will also assist in the task, but, extreme care must be used to prevent bending any fins.

It's a very common problem with M/B radiators due to the very close passages between the fins. My SD is running warm now........nearly all the time.........even at 75° ambients..........without a/c. The culprit is surely the radiator as it has a new water pump.

The fans are never the culprit if the vehicle is at highway speeds.

Yes, anything could have happend in 34k Km's. Heck the car could have sat in a garage and their could be nuts and a mouse nest in between the condensor and radiator.

I thought I posted this yesterday - oh well ...

I think this is a pressure issue:

1. Water pump seal -check for seepage at the weep hole
2. Reservoir leak (above the coolant level) -usually in the area of the neck (the cap could be OK, but still not hold pressure due to another leak)?
3. Head gasket leak - worst case, but could account for the spikes in temperature you are experiencing

Fix cheapest first - 1 and 2, above, are easy and inexpensive. 3 is expensive, but with megamiles, possible.

Mechanic's Advice
 

I spoke with a MB mechanic this morning.

He said it's probably either my Auxillary Fan or the 100 degree Switch.

He suggested I try to turn on the Air Conditioning and then the Auxillary Electric Fan in front of the radiator should begin to spin. This was suggested in the thread earlier. Well the fan didn't spin. The temp guage was at about 60 degrees so it wasn't hot, but I understand that the fan should still spin.

So...I think I have either an Aux. Fan problem, or the 100 degree switch problem.

Can someone give me some insight into these two possible problems? How hard is it to change these two myself. Any insight into diagosiing and fixing would be appreciagted.

Brad.

Doc:

A 1,200 foot climb over 3 kilometers is significant. What is the ambient temperature when the temperature climbs?

Check the link below. Especially items #'s 17 & 18.

http://pages.prodigy.net/jforgione/MB_S500.html

Good luck.

Let us know what worked (if you were able to fix the problem).

drbrad,

Are you replacing anything as we go through these discussions? Likely, you won't find "the" single thing the first time out - I'll watch the discussion and look forward to seeing what you have actually done related to the many things you have heard.

Please let us know how it goes.

Yup
 

Yes, I've been doing almost everything everyone has suggested.

• replaced thermostat with new MB thermostat (opens at 84 degrees celcius)
• replaced rad cap with new MB cap from dealer.
• Flushed rad and changed coolant.
• Checked fans. Appear to be working, at least the one that is behind the rad.
• Trying to figure out if the Aux. fan is malfunctioning. Turned on A/C and the fan wasn't spinning.
• Bought a new 100 degree switch today at lunch and will replace that tonight.
  • Any new suggestions? Thanks to all....
    
    Brad.

Hey doc- an RN from Chicago consulting with you here! Our 190d had similar symptoms where sitting in traffic idling for long periods, and driving up steep inclines at highway speed would cause the temp to climb relatively high on the guage. After chasing several possible causes- I ran her till she got hot, and saw that the fan would not engage. I used a jumper wire to activate the magnetic fan clutch (which clicked beautifully), so the switch that activated the clutch turned out to be the first problem. I replaced it for $40 US. After the AC was repaired she began to overheat again- this time it was a disconnected wire to the pusher fan similar to the one you have described. With these two problems addressed she rarely runs hot- even at highway speed, with 4 passengers, climbing a hill with the ac on. I think you may have found your problem in the switch- with the new cap and flush you've done good preventative maintainence as well. Good luck- John

Problem Solved?
 

Hi guys:

I've solved the problem with assistance from chiro, a member on this forum and everyone else's suggestions. Chiro showed me how to ground out the switch to test if the Aux. Fan was okay and that the switch was malfunctioning.

We grounded the 100 degree switch as recommended by grounding it to the block. Guess what???? The Aux. Fan kicked in and the temperature began to drop.

I will install the new switch tomorrow and let you all know how I made out.

I have to thank everyone for their suggestions and I am looking forward to using my A/C again!

I will recap what symptoms I was having and what we did and how we resolved the problem, once the switch is installed and tested.

Thanks again,

Brad.

Aux fan switch
 

What is the part number for the Aux fan switch? I have the same problem and want to install the 100 degree switch, the car originally came with the 130 degree switch 0085424517, but I want the fan to come on sooner. Thanks

Part Number
 

Hi fbotros:

I bought the part from Mercedes Benz Canada for $55.65 (CAD)

The part number is A 006 545 14 24. ("SWITCH.AUXILIARY FAN")

I still haven't installed it as I have to wait for the engine to cool. It looks relatively easy to install.

I've had the Aux fan grounded and running and the car has remained at a constant 84 degrees all day. It's been pretty hot today 23 degrees celcius, and I've had the Air Conditioning on.

I'll summerize everything once I get the switch installed.

Thanks to everyone!

Brad.

Well, I guess that explains why my auxillary fans do not come on..... my A/C is on the fritz. :rolleyes:

Of course the temp will drop if the aux fans come on, they move a lot of air!

But you are barking up the wrong tree with that one, they don't do anything until 105C. If you are by passing the switch to make the fans run all of the time, you will burn them out. Also this is a band aid at best over the real problem.


Under normal driving the temp should stay between 80C-90C, and the aux fans should never come on. Unless you have the AC on of course, even then they seem to cycle.

Hattie, the aux fan(s) can be tricked to go on at a lower temp than the factory set temp.

See below...

http://pages.prodigy.net/jforgione/MB_CTS.html

I used on of his switches in my fomer 1991 420SEL and it worked just fine in heavy, So. Calif stop and go traffic.

For some reason the W124, with the M103 engines tend to run a tad hotter than othe Benz engines.

So Far So Good
 

Hi everyone:

So far so good.

Here's a summary of what has happened so far:

• the vehicle is a 1982 380 SEL 225,000 KM
• it has been fully serviced for 25 years at MB. (Even all of the oil changes.)
• the radiator was replace approximately 34,000 Km ago.
• about a month ago the car began to over heat and boil over when I drove up a steep long hill to my home. (Approximately 3 Km up to an elevation of 1200 feet.)
• the ambient temperature has been quite hot in the low 20's degrees celcius.
• the car was running between 80 and 100 degrees with normal city driving.
• I spoke to friends and posted this thread for some ideas.
• I first changed the thermostat. I used a MB thermostat that opens at 84 degrees celcius.
• I continued to have the problem. When I drove up the hill, the temperature guage would slowly rise and then spike to just over 100 then fall slightly then rise close to 120 degrees. Occasionally it would boil. (Four times in total.)
• whenever I started the car in the morning or drove down the hill, the temperature remained below 80 degrees.
• I replaced the radiator cap with a MB cap as suggested in this thread.
• no change with the new cap.
• I drained and flushed the coolant. Again, not much change in the symptoms.
• I checked the fan in the back of the radiator to see if the clutch had failed. I checked this by driving the car until it was good and hot, then I opened my driver's side window, opened the hood and reached in to turn off the engine while the hood was open. The fan immediately stopped spinning when the engine was turned off. I am told this indicates that the clutch had not failed.
• Next I was ready to tackle cleaning the radiator from the outside, when I noticed that there was an additional fan (The Auxillary Fan) in front of the radiator.
• I am told that this Aux. Fan helps cool the radiator under very hot conditions when there is insufficient air crossing the fins on the radiator.
• my next problem was to determine if the fan was broken or the Aux. Fan Switch.
• I grounded the Aux Fan switch and the fan spun. I am told by MB that these fans rarely fail. In fact they didn't have any Aux. Fans stocked in Western Canada and if I needed one, they would have to ship it in from Toronto. (Fan cost?.....$600.00)
• This indicated that the Aux. Fan Switch was malfunctioning. (The switch is located on the Thermostat Housing)
• I replaced the switch today and all is well. Switch cost: $55.65 CAD
• The car ran between 80 degrees and 100 degrees all day today. (I did a lot of driving, but the ambient temperature was quite cool at about 18 degrees celcius.)
• The temperature never rose above 100 degrees. When I drove up the hill, the temp rose to 100 degrees and by the time I got to my house, the fan had kicked in and the temp remained at 100 degrees.
  
  I'm pretty sure the problem has been solved. The ambient temperature is suppose to rise to mid 20s this weekend. I'll let everyone know how she fares.
  
  Wish me luck.
  
  I have to thank everyone for their assistance and suggestions. This type of forum is fantastic.
  
  Thanks again....
  
  Brad.

86560SEL:

Try doing what I did. First ground out your Aux. Fan switch to see if the fan works. If it spins, the fan is probably good. Or you could try hooking the fan up to a 12 volt battery and see if it spins.

I've learned that if the fan is good, but it doesn't spin at high temperatures, your switch is probably at fault.

The fan will only spin when the temperature gets too high...and the temp would definitely rise with the AC on. I've been told that the fan doesn't necessarily turn on when the AC is on, just if it gets too hot.

Try changing grounding the switch and let us know if your fan works.

Hatterasguy, you're correct. The fan only turns on when the coolant temperature rises above a certain point. In my case 100 degrees. I ran the fan constantly by grounding out the switch as a short term fix until I could change the switch.

The switch appears to have solved my problem. I'm still not sure if the fan is suppose to run whenever the AC is on, or just when the coolant temp rises above 100 degrees.

Thanks drbrad for the part number, actually my car (89 300SE) uses a different switch, I got the part number from the dealer. I hope that solves my problem. Thanks again.