M.B.Doc/Benzmac/Anybody Help! Tach/Electromagnetic Fan Problem
 

Alright guys. Check this one out.

Was looking under the hood one day with the engine running when I smelled burnt rubber.

Turns out, the wires going to the 2 prong temp sensor on the engine (the one nearest to the front) were burnt. I stripped back the wires all the way back (to the side of the wheel arch) until there were no signs of burning and renewed the wires going back to the sensor. The connectors looked ok so they were re-used.

I have swapped out the sensor, but even before re-connecting the 2 wires, fuse #10 blows (as soon as the ignition switch is turned to position 1). When the engine runs, the tach is out (of course, coz they share the same fuse).

Re-connecting the wires to the sensor does not seem to produce any burning or changes to the situation, but i disconnected them anyway.

The wires from the sensor seem to go back all the way to the back of the battery. Where do they end up? If I knew, I could do a short circuit test on the cable. Also, any switch or device at the other end could be causing the short in the first place.

What about the magnetic clutch, do these foil easily?

For your information, I have swapped out the multiple contact relay (20/30A behind fuses), OVP (to solve stalling problem) as well as the fuel pump relay (stalling). All fuses have also been renewed save #10 which keeps blowing.

Anyway, we're talking about a 1991 190e 1.8 RHD so I hope u guys r able to help me out on this one.

Thanks.

Azhari
1991 190e 1.8
Singapore

Help
 

Help!!!

Azhari
1991 190e 1.8
Singapore

Help???

azhari,

the cooling fan switch you refer to usually fail-mine failed at 100,000miles plus and i changed it and the car no longer runs hot in traafic.

the electromagnetic clutch can fail-if you have a haynes manual for your car,then i suggest you look at it for more info on the fan clutch-there are a couple of electrical contacts below the cooling fan-have you checked the wiring that leads to the fan clutch?

Wires usually burn solidly from the point of short to the point the wire changes size. The exception to this is where high current circuits have bad connections. In the case of a bad connection the connection itself increases the current and causes localized heating. Most temp sensors are low current sensing devices and can't draw any current due to the internal circuitry of the control unit monitoring them.

In the case of temp switches they are current carriers and the way you describe yours, I believe that the connections themselves were the problem. Check the circuit with an ammeter and verify that consumption is less than recommended fuse rating. If in doubt install an inline fuse of smaller rating in a strategic location.

Hey Guys

Tks for your replies.

Sunil - I have the Haynes manual and use it for the more straightforward fixes. I have been a diehard Haynes fan since I bought my first manual for my 1979 Alfa Romeo Sprint 6 years ago. You have the 1.8, would my babybenz be similar to yours? Mine's a RHD.

Steve - you're right about "the switches being current carriers...".

There is only one sensor/switch for the electromagnetic fan, isn't it (the one on the valve cover - 2 prong on my 1.8)?

Could you guys advise on the path in which the cable travels from the temp sensor on the valve cover?

Is it connected directly to the electromagnetic clutch, or does it go thru' a relay?

The cable seems to go back from the side of the car towards the battery and disappears thereafter...where does it go to?

Tks again for your responses. Hope to hear from you guys again.

azhari,

mine is indeed a rhd car

the cooling fan switch on my car has 3 prongs but two wire connectors,is this the same as yours? cost me about 10 british pounds to buy and replaced it myself.

sunil

Sensor
 

Sensor for the electromag clutch is the one on the valve cover, nearest to the front of the car, right?

Mine's 2 prong, and I swapped it out as soon as i discovered the burning wires. It cost me $15 Singapore Dollars and it's original Merc.

I'm trying to figure out whether I can isolate the clutch fan to see if fuse #10 still blows.

If I could only find those dang terminals...:)

Boy, is this gonnabe fun.

Btw, parts and service for the 201s and 124s are really cheap here because they are really common on our roads.

Tks

You guyz know where the wires from the sensor lead to behind the battery?

:confused:

Or should I disconnect the wires to the electromagnetic clutch to see if it is shorting out the circuit?
:confused:

OK.

I just had an idea. Could the electromagnetic fan of my car be wired to be permanently on (maybe by previous owner)? This just came to my mind after I viewed a 190e 1.8 for sale on behalf of my kid brother.

The temp sensor (3 pin with 2 pins for connectors) was seen without the connectors. And the car was running without overheating.

Same goes for mine. I drive the car all day with the air-con on and at 32 to 34 deg C outside and the max running temp is around 89 deg C in stop-go traffic. It doesn't overheat.

And mine has been running with the 2 wires disconnected since the burning incident.

I am planning a long drive up to Malaysia soon and this issus gives me no peace of mind...

Another thing, after driving around town for about 45 minutes the other day, i switched off the car and spun the clutch fan. It moved only about 1/4 turn...?????????

Wouldn't that mean the clutch fan was working?

Yikes. This is freakin' me out.....

But it would be fun to solve this...as with the other problems...as it is, I have no tach till this day and that's no fun!!!

:D

Any ideas?

after 45 minutes of driving,the fan should spin freely with the engine swtched off,that is if you have an electro-magnetic fan clutch .

on a viscous /fluid operated fan clutch ,you would expect a 1/4 turn after 45 minutes of driving.

freewheeling, if engine was cold

i get the feeling that your electromagnetic fan clutch is either faulty or been modified to stay on permanently in the hot weather conditions in singapore.

i know for a fact that in kenya,africa where we had equatorial hot climate,some people would throw out the thermostats and modify fan clutches to come on all the time-not a good idea as you lose engine performance/fuel economy and cause premature engine wear.:cool:

Yep. I have the electromagnetic clutch. The 1/4 turn thing was psycological i guess (after having read to many posts in this forum).:D

I tried spinning the fan again this morning after driving and it does spin. Guess i didn't spin it hard enuff the other day.:o

Well, it may seem that my fan has been wired for good. That has gotta be solved.

Is there a way to see it in action?

Perhaps if i get someone to rev whilst I look at the fan? It should spin with the engine if it is engaged permanently, right?

Waddaya think?

:confused:

My head is spinning right now... :D

azhari,

yes you could ask a friend to rev up the engine to see if the fan is the " on all the time mode".

on my car,there is like a 2mm gap between the magnet and fan assembly-you should be able to tell from this whether the gap is present =fan in freewheel mode or no gap=fan all the time mode. or note.

hope this helps

Interesting...

I'll check it out.

:D

Sunil190e-1.8

Holy crap!!!

The clutch fan is not engaged ALL THE TIME.

It just free wheels and there is a 2mm gap maintained. It doesn't lock-up at all.

I disconnected all the elect. fans and let the temp go up to 110 deg and the clutch fan does not lock up.

I will look at wiring the clutch fan to come on with the high speed elect. fan.

Mods aside, the car does not overheat running with the 2 elect. fans at 30 to 33 deg outside temp. Running temp. is about 85 to 90 deg. If I let the car idle in Park, it will do so without overheating even on a very hot day.

However, it came close to 105 deg the other day when I was stuck in a really longgggg jam...that was too hairy for me!!!

However, with the clutch fan sensor wires disconnected (there is a short in the wires, remember?), the fuse for the tach/clutch fan still blows (no tach). I will still have to trace for the short.

I insist to wire the clutch fan to the elect. fan even if i get the short sorted out coz I am very uncomfortable with the clutch fan's "turn-on" temp.:D

Geronimoooooooo!!!

Damn...
 

I failed, sob...

Haven't found time to trace the short coz Babybenz was whacked in the rear by a truck last week and I just got her from the bodyshop today.

I guess I'll be off to the Merc tech tomorrow to get the short sorted out...

Azhari
Babybenz 1991 190e 1.8

Now we're gettin' somewhere!!!
 

Still trying to get to the short that's causing fuse #10 to blow, therefore, no electromag fan and no tach...

I couldn't find the time to drop Babybenz off at the tech's shop...and by the time I could, it's a long weekend holiday here.

So I took the air cleaner housing out and took a look at all the connections/disconnections at the sensors on the valve cover.

To-date, the electromag fan connections at the sensor have been removed coz they were found burning when the electromag fan was on.Even now, fuse #10 still blows with these connectors to the sensor removed.

Removed a single pin connector and found that it was the engine temp sensor, so I put it back on.

Looked closely at the electromag clutch and traced 2 small wires back to just below the air cleaner housing area. One was to ground and the other went to a small round connector.

Disconnected this wire and renewed fuse #10 and walah!!!! The tach is back!!!

I was really getting into the swing of things when it started to get dark...:(

Damn!!!I was just starting to have fun...

Anyway, tomorrow, I will apply +12V to the wire and see if the electromag clutch engages. I will fuse the wire just in case there is a short in the clutch itself (I doubt the clutch is faulty).

If it works, I guess the short exists in the wire running back to the sensor. If it gets difficult to pull the old shorted wires out, I would run a new wire (fused) from the battery to the sensor, then back to the clutch, and this should work...

This is gonna be fun.

Damn, these cars are really fun to work on!!!

I'll post my findings asap for the benefit of other 190e owners. This should be especially interesting to anyone with a 1.8 like mine...

Geronimoooooooo!!!!

Azhari
Babybenz 1991 190e 1.8

azhari

What did you find regarding your electromagnetic engine fan?

Haasman

Electromagnetic Clutch
 

Haasman

It was a fried electromagentic clutch.

The day after my last post, I tested the clutch by directly applying 12V to the clutch supply wires (the two thin wires) and NO click!

By the way, the supply wires going to the clutch were really stiff and some of the insulation had fallen off in places (due to the heat from the short).

So I went out and got myself a new clutch ($60), a new set of supply wires for the clutch ($10 - this connects to the clutch via connector and the other end goes to the sensor/ground; a straightforward replacement) and drove the car to an indie to get the stuff replaced.

30 minutes and the same amount of dollars (labor) later, it was done.

Having seen how it was done, I figure I could have done it myself but i didn't wanna fiddle with the belt.Having seen how the belt is taken off, tensioned, etc I feel more confident if I ever need to replace a water pump or whatever...

Anyway, running temp. is around 82 to 85 deg C and the ambient temp. where I come from is about 30 deg C.In stop-go traffic, the temp is between 85 to 90 deg but never close to 100.

Cool.

Azhari
Babybenz 1991 190e 1.8