Today, I found out the AC on the 99 ML isn't working. I swapped relays and checked fuse 44. No dice. The compressor does not kick in nor does the aux. fans work. I have some possibilities.
1. The aux. fan(s) could be bad, but unlikely, causing the compressor not to kick in when the AC button is pushed.
2. The compressor could be low on charge/ bad causing the Aux. Fans not to work.
Anyone have any additional thoughts and possibilities as to what could be the problem?
__________________ Be careful about reading health books. You may die of a misprint.- Mark Twain
Today, I found out the AC on the 99 ML isn't working. I swapped relays and checked fuse 44. No dice. The compressor does not kick in nor does the aux. fans work. I have some possibilities.
1. The aux. fan(s) could be bad, but unlikely, causing the compressor not to kick in when the AC button is pushed.
2. The compressor could be low on charge/ bad causing the Aux. Fans not to work.
Anyone have any additional thoughts and possibilities as to what could be the problem?
I too thought all of the above was wrong but it ended up bieng the aor blend moter actuator.
One day my ac just stopped working and onl hot air would come out the vents even after pushing the ac button. I took my 99 ML into an AC shop to check for leaks and none were found, lucky for me. So then I did some research and found that MBUSA had put out a DIY repair a few year back due o this problem on many ML models.
here it is buddy. I just saved you time and money, and if your patient I will upload the Video DIY of me doing this repair on my ML in the next week.
Part number is: A163 820 0108
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jealous people can suck a fat one!
While it is possible that one of the actuators has gone bad, it may be worthwhile to check the pressure/charge in the system. Possibly, you are just low on the refrigerent. I am assuming that you don't have a pressure guage, take it to any competent mechanic and have them recover the old oil and refill the system. During that procedure, they can tell you if there are any leaks in the system. I would say the cost may be around $80.
When was the last time you used your A/C? If you haven't used it in a while, then I would suspect there may be a [tiny/slow] leak, leading to low on refrigerent, leading to aux fans not being activated, leading to no A/C. :-)
I too thought all of the above was wrong but it ended up bieng the aor blend moter actuator.
One day my ac just stopped working and onl hot air would come out the vents even after pushing the ac button. I took my 99 ML into an AC shop to check for leaks and none were found, lucky for me. So then I did some research and found that MBUSA had put out a DIY repair a few year back due o this problem on many ML models.
here it is buddy. I just saved you time and money, and if your patient I will upload the Video DIY of me doing this repair on my ML in the next week.
Part number is: A163 820 0108
Thanks for the info. I went ahead and downloaded the PDF.
But, I'm getting 'cool' air out of the vents and the temperature settings are working because I can change it from cool to hot, etc. The cool air is the outside air being pulled in. How I first noticed it was when it was raining, the inside window wouldn't defog as well as it had been (need a/c for that). Then, yesterday, the car was hot from sitting in the sun and when I turned on the a/c button, just barely cool air came out (outside temp. air). I checked the compressor and it's not running at all.
I'm really suspicious of the recent oil cooler leak I had and the repair the dealer done on it. I'm wondering if some oil had gotten into the compressor wiring harness plug and caused a connection problem. I'll check it today.
Does the Air Actuator have anything to do with the compressor not running, i.e. a switch or something?
While it is possible that one of actuators has gone bad, it may be worthwhile to check the pressure/charge on the system. Possibly, you are just low on the refrigerent. Take it to any competent mechanic and have them recover the old oil and refill the system. I would say the cost may be around $80. During that procedure, they can tell you if there are any leaks in the system.
When was the last time you used your A/C? If you haven't used it in a while, then I would suspect there may be a [tiny/slow] leak, leading to the low on refrigerent, leading to no aux fans working, leading to no A/C. :-)
MB compressors are supposed to run some, even with the heat on, to keep them from freezing up from no use. I do know it was working a couple of weeks ago, but as I mentioned in my response to DETANE, I had an oil cooler leak the dealer fixed last month and some oil may have gotten in the wiring harness plug. If the plug checks out okay, I'll run it over to my independent and let him work on it.
It's amazing how unpleasant a place the interior of a vehicle can be in the sun without air conditioning - I know this living in West Africa where it is often 35 degrees centigrade in the shade!
Please let us know how you resolved it when you do.
MB compressors are supposed to run some, even with the heat on, to keep them from freezing up from no use. I do know it was working a couple of weeks ago, but as I mentioned in my response to DETANE, I had an oil cooler leak the dealer fixed last month and some oil may have gotten in the wiring harness plug. If the plug checks out okay, I'll run it over to my independent and let him work on it.
cmitch, if all the fuses and relay are good, and the A/C system is fully charged, then I believe that you have an electrical issue with your A/C system. I think you are sharp enough to know if your compressor is running or not, and with that said, any issue with any actuators is not relevant here.
Something is preventing the signal from the AAM to activate the fans and the compressor . You were correct with your original assumptions (cooling fans or low or no charge). I do not think that the cooler lines (assuming you are referring to the P/S lines) would cause the problem because the cooler lines are on the driver's side and the compressor is on the pass. side.
My suggestion would be is to check the fans and compressor separately.
The Fans----go to them and find the wire connector (green wire & brown wire). Fashion a jumper wire from the pos. battery cable to the GREEN wire at the connector. The fans should run, because the fans are wired together to one plug, and I doubt both fans seized at once. Then remove the fan relay K26 and apply battery power to the cavity which corresponds to the #5 prong on the relay or #87 on the relay (depending on what make relay you have). Look at the black plastic where the prongs are on the relay and look for 5 or 87. Where that prong goes, if the relay were inserted, is the cavity that has to be powered.
The Compressor----the compressor has one wire, Brown/Violet. Separate the connector where it plugs into a pink wire, and then apply battery voltage to the Brown/Violet wire. The compressor should run regardless of what amount of charge you have in it. Once you see it run, remove the power lead.
If everything checks out but still no A/C, then post back and I will give you the procedure for checking the A/C control module.
Thanks for the info. I went ahead and downloaded the PDF.
But, I'm getting 'cool' air out of the vents and the temperature settings are working because I can change it from cool to hot, etc. The cool air is the outside air being pulled in. How I first noticed it was when it was raining, the inside window wouldn't defog as well as it had been (need a/c for that). Then, yesterday, the car was hot from sitting in the sun and when I turned on the a/c button, just barely cool air came out (outside temp. air). I checked the compressor and it's not running at all.
I'm really suspicious of the recent oil cooler leak I had and the repair the dealer done on it. I'm wondering if some oil had gotten into the compressor wiring harness plug and caused a connection problem. I'll check it today.
Does the Air Actuator have anything to do with the compressor not running, i.e. a switch or something?
YES.. It will not open the flap that allows the cold ac air into the cabin. My truck had all the symtoms your truck is having. I asked the dealer and he said if im getting cold air then the ac system is good even if its a little cold air. I noticed on mine when I turned it to the cool setting and put the vent on low while switching the ac on, I actually got really cold air. But then when i turned the fan speed to high I heard the flap shut and only hot air came into the cabin from the engine.
cmitch, have you visually checked to see that the compressor is not engaged? If you have then a flap problem does not come into play here. In Detane's case his compressor was working, but because of the actuator problem, he was not getting the correct air temp. delivery.
cmitch, have you visually checked to see that the compressor is not engaged? If you have then a flap problem does not come into play here. In Detane's case his compressor was working, but because of the actuator problem, he was not getting the correct air temp. delivery.
Thanks for all the info. I took it to my indie today and he put his fancy, smancy A/C recovery unit to it. It was .7 lbs. low (holds 1.7 lbs.). He recovered the freon and He pulled a vacuum, recharged it- No go. He then put his sniffer tube around it and found numerous (tiny) leaks all around the compressor. He then went to check the compressor- it is seized-toast-fried. Even with the pressure out of it, he couldn't turn it. He said the leaks were the result of the locked up compressor.
What's strange is I've had NO symptoms the compressor was going bad. No rattling, knocking, squealing- nothing. I KNOW it was working before I took it in to the dealer, hence why I was suspicious of that. The car has 182,000 miles on it. If it is the compressor, I really have no reason to complain since it has been an, overall, good vehicle.
I guess my next question is: How do you feel about a rebuilt Bosch compressor? My indie insists I'm much better off with a new one since he said rebuilt ones fail about 60% of the time. Plus, we'll have to replace the entire system (dryer, filter, compressor, clutch) or the manufacturer will not stand behind the new or rebuilt compressor. Do you have a source for a NEW compressor?
Air conditioning not working 
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