Mercedes 190 E a/c problems

[Scott_in_WVA]

I have a Mercedes 190 E,and earlier this past spring I had it in the Mercedes dealership for some work and they put a whole new ac unit in...New compressor,evaporator,and (condenser?)
It will work fine at times and then it will quit cooling and start blowing warm air in the car and you have to put the windows down,then after while it will start blowing cool air again.I had taken it back to the dealer once already and they had it set there for 2 days and they said it worked fine...Well I stopped by the dealer Friday and made an appointment to have it looked at again...they say,we will look at it again,but its hard to trouble shoot it does not quit working right while they have the car in the shop, well I understand that...but I can not always be at the dealer when the problem occurs, I have a feeling it is going to be the same story again.
Anyone know of any suggestions or things to look for on this car in regards to this problem?Could it be a sensor or low on refrigerant?
Thanks
Scott

 

[centex]

I had a 190 and the AC was replaced three times in two years. Fortunately it was under warranty and did not cost me anything. The first time it was replaced I had the same problem as you. It has been my experience that this usually means that the freon charge is low and the evaporator freezes the condensation on the coils. When the ice melts the AC will cool until it freezes up again. In this case I found a fitting on the condenser that had oil on it indicating a bad o-ring. I pointed this out to the dealership but they replaced the entire AC anyway. I assumed they got more money from the distributor this way. I had to take the car in later for a AC recall and another time for a safety recall and they replaced the entire AC on both occasions. I concluded that the AC in this car was beyond hope and got rid of the car before the warranty was up. I thought that Mercedes made a good car before I bought the 190 but I would not take one if someone tried to give it to me free. I had more problems with this car than any car I have ever owned. I now think Mercedes and all the German cars are overpriced junk. I have never seen a German car that the interior trim was not falling apart on even in the dealership and you even had to look hard at the Mercedes in the showroom to find one that was not already starting to rust at the seams near the trunk. Just my opinion but I would get rid of the 190 bvefore you put more into repairs than it is worth.

 

[Scott_in_WVA]

I love the 190E,the a/c is the only problem I have...but thanks for the info about the air.

 

[centex]

I should point out two potential problems with this car to maybe save you some grief down the road.
1) If those spherical wheel lugs are overtightened you will not be able to remove them with a lug wrench. A dealer's mechanic overtightened mine and I bent the lug wrench Mercedes gave me and could not budge them with my largest impact wrench. I took the car back to the dealer who overtightened them and he also had problems until he used an impact wrench with the air pressure set to 160 lbs. If my wife (or I for that matter) had had a flat on the road it would have meant a tow truck because the wheel could not have been removed. So make sure that no one tightens those lugs more than the recommended torque.
2) I had a similar problem with the oil drain plug. As I remember this is a relatively large diameter bolt with a large shoulder that seals on a copper gasket. The head is small though and a soft metal. I think it is 12 or 13mm. They made it this way so it would not be overtightened but the dealer's mechanic overtightened it anyway. I had them change the oil at the required 6K mi intervals to ensure that the warranty was not invalidated but I changed it at the intervening 3K mi. Even using the correct size 6 point socket I rounded the head of the oil change plug. I had to use a hole saw to cut the shoulder off to remove the bolt. Again the torque value that Mercedes gives for this fitting is very important due to the design of the bolt.

I have tried to forget this car but now more horrid details are comming back to me. I should also let you know that you should not let the brake pads wear the point that the wear sensor turns on the light. When this happens you have to replace the sensors and they cost more than the brake pads which in turn cost more than 4 or 5 sets of normal pads although they last only 1/3 as long.

I hope I don't have nightmares about this car now!!

Oh yes, if you have the all inclusive alarm system that also protects the radio (this was the most stolen radio in the US when I had my car), don't let the battery go dead with the alarm on or your radio will be disabled and you have to take the car to the dealer to get it replaced. I thought it was interesting that the alarm system that was supposed to protect my radio out destroyed it in less than 2 years when I have never had a radio stolen from a car in over 40 years. For my money I would not have an alarm system on anything. My Corvette came with an alarm but you had to turn it on and off with a key at the rear of the car. I used it religously for a while but I would occasionally forget to turn it off. I then started to notice that even with the alarm blaring at 120db people would barely give it a notice, i.e. it did nothing towards stopping someone from stealing my car. When I lived in London the insurance companies there charged more for homeowners insurance if you had an alarm bell mounted on the building. They said that the appearance of an alarm just told potential burglers which houses had valuables worth stealing.

 

[Rowski]

Scott

What year car? R-12 or R-134a? Has it been retrofited? When does it seem like it is not cooling, stop and go traffic or highway?

 

[Scott_in_WVA]

Yes it has been retrofited,all new everything (1986)
It happens on the open highway or sitting in traffic...whenever it decides to do it.Nothing consistent....

 

[Carl_NH]

Scott,

Could be moisture in the system that when the expansion valve gets cold it freezes and is blocked, then when the engine heat warms it enough the refrigerant flows again.

Or could be a slow leak and you are low on refrigerant.

Check out the car by opening the hood and cooling on high, then feel the return line - it should be cold all the time. Also the line to the expansion valve (high side) should be warm to the valve and cold at the valve and after that point.

Good Luck,

carl

 

[Scott_in_WVA]

Thanks Carl.../w3tcompact/icons/smile.gif

 

[8NTX]

A few years ago I was looking into used 190's for my daughter. Of the three that I test drove, all had A/C problems. Also drove a 300E that had the same problem. Gave up on Mercedes and got her a Honda - no problems. But I would disagree that all German cars are junk. My wife has been driving a 2000 BMW 528I for almost three years. It is absolutely the finest car I have ever owned or driven. A true driver's car and the best handling car on the market, IMHO. She preferred her Lexus ES300 because of the easier steering.

 

[dmccarty]

Scott,

Car Talk on NPR just had this question for a different car this
weekend. IF the AC fails when the engine is at idle then its
likely low refridgerent. If it is when the engine is above idle
its likely to be the compressor. Of course if the refridgerent is
low the question is why? Does it have a hole in the
compressor?

You might try a search on the Internet for a Mercedes User
Group website. I know of a few sites for Ford, Chevy and
Dodge trucks as well as one for VW TDI diesels. I would bet
that there is a Mercedes site. These sites might be able
to tell you if this is a common problem with a particular car.

Good Luck,
Dan

 

[Scott_in_WVA]

Thanks to all of you!!!!

 

[centex]

I only looked at Mercedes, Porche, Audi, and VW. I drove a VW for 100K miles but it was really a crappy car. Fortunately it did not have too many things to break. It was good on tires though. The Porches were falling apart in the showroom around their outrageous price tags. I had two friends who had Audi's and they both had some bad problems. I sat in a 500HP Audi at one of their factories in Germany. It was an impressive car with an impressive price but given my friends' experiences I would not have wanted it. I wanted a BMW but they started out as an inexpensive drivers car and I found it hard to think of them as being worth what they cost now but then I don't think any car is worth what they cost now. I now only buy old Japanese cars to drive. They seem to run forever and almost never break which is fortunate because the parts are very expensive. I think my 1972 Corvette is still the best car I have owned. I bought it new and have driven it for 350K miles and it never broke down on me until I got close the 350K miles. I finally had a rear wheel spindle break and had to call a tow truck. Fortunately the heavy duty disk brakes on the car kept the wheel from comming off. I would like to see a modern car's brake caliper do that! The worst car I have owned was a 1967 GTO. It was a piece of junk from the gitgo and I could not ride in it for 30 minutes without getting the worst back ache from the seat.

 

[karmakanic]

Hi Scott,

The a/c system used on the 190 is an unusual system. Basically MB tried to design an auto climate control system that used electronic control of the a/c system and mechanical control of the heater system. They mix the cold air and the heated air to get the desired vent temperature. To do this, they needed a feedback potentiometer in the heater circuit (which is vacuum controled) to tell the a/c system what the heater system was doing. Your problem likely is coming from this feedback potentiometer That is why it blows warm air when it acts up. These potentiometers were notorious for causing the symptoms you describe. The problem is, they're located on top of the heater housing, just underneath the dash covering. To replace them, the dash has to be removed.
There is an adjustment on them, which can be made with the dash in place, if the mechanic knows the tricks to get access.

Now, I'm not saying this is your problem for sure. Other things, like in car temp semsor, outside air temp sensor, push button control unit, ect. can cause similar symptoms. It will be necessary for someone to work with the car until the problem occurs. At that point, a few quick tests by someone who knows the system can determine the problem part.

Frankly, the dealership is not the best place to get a problem like this resolved. For one, the dealer techs are not inclined to spend the time necessary to get the problem to occur. They take it for a drive around the block and if the problem doesn't occur they send it back to the dispatcher with "no problem found" And the turnover in a dealership means most of the mechanics were still in high school when that car was built. The old guys in the shop know to run and hide when the dispatcher shows up with a 190e a/c problem, so the less experienced mechanics get assigned to the job.

My .02 advise is to hunt up an independent shop that's been around for a while and specializes in German cars. There's usually one around, since although Mercedes is the best car built in this world, they do break pretty often.

HTH
Dave Perry aka karmakanic

 

[Scott_in_WVA]

Thanks Dave....
I appreciate the info/tips and advice.....there is a foreign car specialist nearby...I will call him.
Scott

 

[Rowski]

Scott

Dave's advise is most excellent. As Dave mentioned the a/c system is very unssual in that uses both electric and vacuum. It's kind of like the the feed back carburator, great when it works... a pain when it doesn't. It would be nice if you find out whether its the compressor control that isn't working or the actual blending of the air. As an example the compressor will not run if the coolant temp is above 115C, the low pressure switch is open, the engine is running at full throttle, the compressor clutch speed is different than engine speed. So if any of these sensors are not up to snuff then no (or intermittent) a/c compressor. There are also many other things on the heater side as well. Another thing that comes to mind is the the conditions of the vacuum lines to and in the climate control system.

You might give <A target="_blank" HREF=http://iatn.net>iATN</A> a try use the shop locator to find a good shop. I use iATN a lot for work. If you need more info about your car's a/c system I have a copy of the wiring diagrams, etc. Send me a private e-mail.

Lets us know how you made out!

 

[Scott_in_WVA]

Derek,
I really appreciate what you have told me and Dave as well..I feel like I am getting somewhere now.
If I need the diagrams I most certainly will e-mail you.
Thanks again
Scott

 

[karmakanic]

Hi Dereck,

Thanks for the kind words.

Nice to meet a fellow iatn member here.

And Scott, do keep us informed how it goes with your problem. I also would be glad to help by email if needed.

Sincerely,
Dave

 

[Scott_in_WVA]

I am still working the a/c problem...been a busy summer.But plan on calling a foreign car repair specialist Monday.I have not drove the car that much.When the a/c works it works fine.