1998 E300 TD A/C Help Needed - PeachParts Mercedes-Benz Forum

mdmccool · #1 07-27-2016, 02:42 PM

Hi Guys-

I recently purchased a nice 1998 E300 TD and have most of the bugs worked out and it is running and driving very well. The last problem is the AC system. It seems to behave erratically which makes it difficult to diagnose.

When I purchased the car the AC system was completely empty of refrigerant, so a friend and I pulled a vacuum on the system for about 30 mins and refilled the system. The AC seemed to work OK for a day or so, then the driver's side vents became warm, passenger stayed cool. Put the gauges on and both high and low sides were out of whack from what they were from the day before. I replaced the expansion valve, vacuumed and refilled the system again and the air worked again. The following day, back to unbalanced air temp between the left and right sides. I took it for a ride and monitored the system pressure through the climate control. While driving about 55mph, the pressure would drop and stay in the 3-5bar range, sometimes down to 2 bar, air would be on the warm side. As I would stop for a traffic light, the pressure would climb to the 17-18 range, air would get much colder, and as I started to drive again the pressure would drip back down to 3-5 and the air would warm.

Yesterday morning I started the car and watched the pressure at idle - it sat around 7 bar, then cycled very quickly to 25+ bar, and the compressor shut off.

Then yesterday evening I started and idled the car in preparation to gather sensor data for this post, and the pressure started on the low side, about 8 bar, slowly cycled down to 3 bar, then rose to 17 bar and cycled between 10 and 17 bar and the air seemed quite balanced and nice and cold.

Sensor data is as follows in C, 83 deg F ambient temp (as reported on the dash) vehicle at idle for about 5 minutes:

Sensor 1 = 28
Sensor 2 = 33
Sensor 3 = 14
Sensor 4 = 12
Sensor 5 = 49
Sensor 6 = 71
Sensor 7 = cycles up and down 10 - 17 bar
Sensor 8 = 71

Code - B1232

Am I correct that sensor 5, Evap temp is reading high at about 120f?

B1232 is a faulty pressure sender - I am wondering if it is indeed faulty or just the erratic pressures are fooling the system into thinking the sender is bad???

I am also wondering if I have a refrigerant leak or is it possible that the system is slightly undercharged?? Anything else come to mind?

This is my first experience diagnosing an AC system so any thought are greatly appreciated.

Thanks,
Matt

compu_85 · #2 07-27-2016, 02:50 PM

Does that car have a variable displacement compressor? The later gas W210s did. If the refrigerant control valve in the compressor screws up the compressor will unload and do very little pumping.

If the high side is shooting up really high while the low side goes low there's a blockage in the system someplace, probably on the high side.

-J

Zulfiqar · #3 07-27-2016, 04:22 PM

seems like a pretty severe clogging somewhere in your system if the pressure shoots to 25 bar on the liquid side.

considering your post claims that the system was empty Im suspecting a stop leak product in there which is causing this behavior.

If the A/C hasnt been used for a while the compressor front seal will be leaking due to being dried out. But in any case a leak test and flushing is required now. If there is stop leak in the system then do not open it up unless you have a proper flushing setup ready to fire at it.

jay_bob · #4 07-27-2016, 04:24 PM

Mine did all that stuff exactly like you described until I completely rebuilt it.

The compressor grenaded which forced my hand as summer was bearing down last May.

I think you are going to find that there is an obstruction or failed component - my evaporator was leaking because there was green streaks on the evaporator.

http://www.peachparts.com/shopforum/diesel-discussion/377507-w210-compressor-seized.html

I was able to do all the work in about 3 days and except for cross threading a fitting into the dryer I would have been done in 3 days instead of having to go back a week later. Now I'm riding with 35 degree discharge air when it is high 90s and oppressive humidity here.

funola · #5 07-28-2016, 08:58 AM

Quote:

Originally Posted by Zulfiqar

.................If there is stop leak in the system then do not open it up unless you have a proper flushing setup ready to fire at it.

Is this for concern of the stop leak hardening up in the open system while being exposed to moisture? What is the proper procedure (type of flush and how soon after system is open) in flushing an open system with stop leak in it? Have you actually seen stop leak hardening in an open system?

I did some googling and found this http://aircondition.com/knowledge_base/LeakSealers.html where a few manufacturers of stop leak products answer questions. 17 and 20 copied below. What do you think? Are the manufacturers lying?

"20. Suppose a system has been treated with sealer but then is opened, and left open for a few days, in a high humidity area. The refrigerant is recovered but not all of the oil. Will the sealer that is in the remaining solidify because of the humidity and become a problem when the system is reassembled?

Cliplight : No. High humidity in a fully open system will not cause the sealer to activate. It takes a leak to generate the concentrated condensation.

Cryo-Chem: A wet dryer can deactivate the Cryo Seal and prevent it from ever reaching the leak site. See answer to #17.

Tech Chemical: No, it will not. Leak Stop rejuvenates the O-rings, seals and gaskets, it does not solidify in the A/C system."

"17. Most importantly: Will parts of the sealer solidify in the system (contact with moisture), float around and eventually plug up a TXV or FOT?

Cliplight: No, the concentration of moisture in the system is too insignificant to activate the product. (See 1, referring to extreme concentrations.)

Keep-it-Kool: There is a potential of the sealer attaching itself to a very wet desiccant bag. Our instructions advise that on old systems that may not have received ongoing service, a replacement accumulator or drier would be an advantage. We have found no indication of any particulate causing problems with the systems.

Tech Chemical: No."

leathermang · #6 07-28-2016, 10:15 AM

There is the potential for that supplier to have been answering EXACTLY the questions which were asked in order to promote his product...
and Tire sealers which I have used on farm equipment were made to harden when exposed to AIR... moisture made no difference....
So opening up the system to air might cause a problem .... and clearly the people questioning were not really up on automobile AC design asking about a ' wet ' receiver dryer.... which is oil wet by design but meant to take out water in the system.

Demothen · #7 07-28-2016, 10:36 AM

My system was open to air for a bit before I flushed it, I found at least 2 or 3 giant clogs from stop leak. It's certainly not going to hurt to flush it ASAP.

I ended up using about 4 cans of aerosol flush. If you get a system that lets you recycle the flush, I'd suggest recycling the flush until it's mostly clean, then adding fresh flush for the final cleaning(s)

Speaking from experience, replace anything that MIGHT be suspect if at all possible the first time, it will save you time and money in the long rung.

leathermang · #8 07-28-2016, 10:44 AM

Quote:

Originally Posted by Demothen

....I ended up using about 4 cans of aerosol flush. If you get a system that lets you recycle the flush, I'd suggest recycling the flush until it's mostly clean, then adding fresh flush for the final cleaning(s).....

The FSM is pretty much ' talking to ' a dealership which is assumed to have one of the recycling flushers....and that is the ' philosophy ' stated in their instructions also....

Zulfiqar · #9 07-28-2016, 11:31 AM

Quote:

Originally Posted by funola

Is this for concern of the stop leak hardening up in the open system while being exposed to moisture? What is the proper procedure (type of flush and how soon after system is open) in flushing an open system with stop leak in it? Have you actually seen stop leak hardening in an open system?

I did some googling and found this https://scontent-sea1-1.xx.fbcdn.net/t31.0-8/1501249_797696356913374_551110285_o.jpg where a few manufacturers of stop leak products answer questions. 17 and 20 copied below. What do you think? Are the manufacturers lying?

"20. Suppose a system has been treated with sealer but then is opened, and left open for a few days, in a high humidity area. The refrigerant is recovered but not all of the oil. Will the sealer that is in the remaining solidify because of the humidity and become a problem when the system is reassembled?

Cliplight : No. High humidity in a fully open system will not cause the sealer to activate. It takes a leak to generate the concentrated condensation.

Cryo-Chem: A wet dryer can deactivate the Cryo Seal and prevent it from ever reaching the leak site. See answer to #17.

Tech Chemical: No, it will not. Leak Stop rejuvenates the O-rings, seals and gaskets, it does not solidify in the A/C system."

"17. Most importantly: Will parts of the sealer solidify in the system (contact with moisture), float around and eventually plug up a TXV or FOT?

Cliplight: No, the concentration of moisture in the system is too insignificant to activate the product. (See 1, referring to extreme concentrations.)

Keep-it-Kool: There is a potential of the sealer attaching itself to a very wet desiccant bag. Our instructions advise that on old systems that may not have received ongoing service, a replacement accumulator or drier would be an advantage. We have found no indication of any particulate causing problems with the systems.

Tech Chemical: No."

those questions and answers dont quite add up..

they are relying on moisture in the system to activate the product? Or are they relying the decompression from the leak site for the product to activate and build a patch.

leathermang · #10 07-28-2016, 11:37 AM

Quote:

Originally Posted by Zulfiqar

those questions and answers dont quite add up..

they are relying on moisture in the system to activate the product? Or are they relying the decompression from the leak site for the product to activate and build a patch.

That is what I was saying.... it makes no sense to rely on moisture to activate a leak stopper... seems like oxygen is the logical activator... and the supplier was skirting the issue trying to make their product seem better...

tjts1 · #11 07-28-2016, 01:04 PM

If you're getting differents left and right temps it's a vent issue, not an AC issue. The 210 has a single evaporator and separate air paths for the left and right vents that can be be controlled separately.

Zulfiqar · #12 07-28-2016, 01:21 PM

Quote:

Originally Posted by tjts1

If you're getting differents left and right temps it's a vent issue, not an AC issue. The 210 has a single evaporator and separate air paths for the left and right vents that can be be controlled separately.

The W210 has separate vent paths on the evaporator, and it is known that when the refrigerant is low the driver vents will be warmer than the passenger side, this is because the evaporator is divided with a horizontal passage. and the evaporator wont be chilled evenly when its on low charge.

bsmuwk · #13 07-28-2016, 02:28 PM

Quote:

Originally Posted by Zulfiqar

The W210 has separate vent paths on the evaporator, and it is known that when the refrigerant is low the driver vents will be warmer than the passenger side, this is because the evaporator is divided with a horizontal passage. and the evaporator wont be chilled evenly when its on low charge.

This right here ^^^ You're undercharged / leaking. If you guys vacuumed the system down, did you wait to watch the gauges for 5-10 mins to see if it's loosing that vacuum?

Why would you charge an empty system without changing the drier? They're cheap and you get to throw some new seals on the lines in that area. Do a bit of research on drier function, with an empty system (for who knows how long) that damn thing has got to be blocked up. Either way, with the system running, look at the sight glass. There shouldn't be any bubbles (barely any bubbles) running through with a charged system. If you've got white bubbles, you're low. Stop filling when the sight glass runs clear or has a minute trace of bubbling running through.

Add dye to the system, get yourself a UV/blacklight or something and start searching for any leaks.

Demothen · #14 07-28-2016, 02:58 PM

I agree that the FSM calls for the refridgerent flush, and that is probably the best idea. No questions. However taking the system apart and flushing it then blowing it dry is better than nothing, if done properly.

vstech · #15 07-28-2016, 06:36 PM

Follow jaybob's advice...

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