My A/C stopped blowing cold air. Checked the fuses......the 30 amp fuse for A/C was blown. I replaced the fuse. Still the A/C is NOT blowing cold air.....please help in diagnosing....or if any one has seen the same thing please advice what I should do. Thank you.

What is your center vent temp with the blower set on two or three while driving? What is the ambient temp? Is the clutch on the compressor engaging, ie is the compressor operating?

Check that fuse again. Chances are, it's blown again. There is a wiring harness upgrade that will bump that fuse up to 40 amps. Do not simply put in a higher amperage fuse, as that could cause a fire.

The vent temperature is 75 degrees. The compressor does kick on. The temp. sensor lights up and goes off when you turn the ignition.....meaning the red led on the lowrange/aux switch panel.......the fuse is fine now after I replaced and it did not blow the fuse again.........I have also tried to take it to hot and dropped it down to cool into the blue range and it cools to 75 degrees when its not hot outside.....otherwise the temp inside is 90 degrees

I think what I would do next is connect a set of hoses with the manifold gauges to the high and low pressure service ports and get some readings. When you take the readings see if you can have the engine rpm between 1500 and 2000 rpms. If the ambient temperature (temperature as measured about 2 inches in front of the condensor), with both fans running is
between 90 F and 100 F see if the low pressure is 30 psi and if the high pressure is between 165-270 psi.

Maybe you are just low on R 134a.

Hi,

I took it to Sears to charge the Freon and he stated that the compressor does not come on so he could not do anything. I checked the fuse again and it is in tact.....any suggestions.....thanks.

Time for more of an expert opinion.

You might want post your questions on this forum for the link below.

Automobile A/C forum

I know the compressor will not come on if there is not enough gas in the system, in other words you initially charge with the compressor off but I'm assuming they tried that and your problem is elsewhere.

1. Can you tell me where the low pressure switch is located.
2. I was told that the clutch could be shorted out and that you have to replace both the compressor and clutch .....further when I enquired about pricing ...the clutch was $749 and the compressor and clutch was $849......
3. Can you tell me where I can get rebuilt compressor and clutch.

Thank you

1-Not sure where the low pressure switch is on ML; on my 300E it is located right on the receiver/dryer as is the high pressure switch.

2-Price for the compressor I recently purchased for 300E was $355. with the clutch being $104. Add to that was a core charge of $93 which was refunded when I returned the parts I removed. The compressor I purchased was a Denso remanufacted compressor. What was important to me was that it was remanufacted by Denso in Japan, which it was. Lots of companies remanufacter Denso compressors but I figured the best ones came from the orginal manufactorer, hope I'm right. Frankly what I put on looked brand new. The compressor does not have the clutch installed but it's not that hard to install.

3- I got my parts from Phillips a mercedes dealer in Virginia Beach. I felt it was best to buy an item like this from the dealer and frankly I think their price on this item was less than I could have gotten it elsewhere.

I do recommeded putting in a new receiver/dryer at the least and a new expansion valve too.

Thanks for all your help. The A/C is fixed now. It was a loose connection underneath the relay switch which is close to the A/C fuse. The compressor works fine and cools very well. I took it to one of my old mechanics and he fixed unlike all the other dealers (2 dealers I checked with....thank goodness I took the car back from them when they said compressor and clutch) and a work shop who wanted to replace the clutch and compressor. I would like to send a bill to the worksop and dealership for wasting my time and would have replaced the compressor for nothing. Beware of dealerships !!!!!!!!!!!

A dealer in MA said the estimate is $1400 for A/C compressor replacement.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

I have a simular A/C problem and would like to explore the loose connection as reported near the a/c fuse. Can anyone tell me exactly where this relay is and how difficult is it to check or repair?

Hello....this sounds exactly like the problem I am having with my wife's ML320. I know its a short somewhere in the fuse box because up until two days ago, when the compressor would refuse to come on, I could tap on the fuse box and the compressor would miraculously wake up! We had done this for the past year....but I guess the short is in a position now where a tap will not work any longer. Can you please describe how I could check to see if something is grounding out under the fuse box? Also, I know about the F44 fuse, and that fuse is not blown....I checked it, and it is not blown, but there is a relay that clicks when it is taken out and reinserted....K19...I do not know if this is where the short might be....has anyone attempted to lift up the fuse box board to reseat or check wires????? Please post or email me if you can provide any help. Thanks...I am letting wife use my S320 right now, and I would like to get hers fixed so I can get my car back.

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1994 S320
131K miles

1998 ML 320
126K miles

1994 Blue C220
122K miles

Im going to Grad School @ the University of Iowa
Go Hawkeyes!!!