Just my luck...so, what's the bad news???

[NoSpeedLimits]

I am picking my car up this evening after the shop is done putting the finishing touches on my new paint job. Yippy!!! Obviously, I am going to want to show her off. Hence, my dilemma... Prior to dropping her off I learned that my A/C was not working properly - only blowing hot air. And since it 90 degrees outside, I need help. I had asked some questions on this forum last month, http://www.bimmer.info/forum/showthr...light=a%2Fcand and based on the responses the first thing I decided to do was have the A/C system recharged. Consequently, I found out that my auxiliary fan was not working. So, I bought the replacement ballast resistor for the aux. fan and picked up a new aux. fan switch socket (figured I'd replace it while I was doing A/C maintenance). I have plans to replace them this weekend. Anyway, the mechanic that did the recharge just informed me that it did not solve the problem. So, he took a peek at the compressor and noticed that the clutches were not engaging. The mechanic suggested that it could possibly be an electric problem. But wasn't sure... He mentioned that the A/C fuse was good, and that he did not know if there was anything else electrically that could be preventing the clutches from working. He indicated that it could possibly be related to the A/C switch mounted in the dash??? Any advise would be really appreciated.

[DanDombrowski]

Hate to break it to ya, but its probable that the thing is out of refrigerant. Most newer cars will keep the compressor from engaging if the system is too low. You can test this easily by testing the wire that goes into the compressor with a volt meter. If it has power, but no clutch, chances are its empty. If no power, its electrical.

Hope this helps.

I am picking my car up this evening after the shop is done putting the finishing touches on my new paint job. Yippy!!! Obviously, I am going to want to show her off. Hence, my dilemma... Prior to dropping her off I learned that my A/C was not working properly - only blowing hot air. And since it 90 degrees outside, I need help. I had asked some questions on this forum last month, http://www.bimmer.info/forum/showthr...light=a%2Fcand and based on the responses the first thing I decided to do was have the A/C system recharged. Consequently, I found out that my auxiliary fan was not working. So, I bought the replacement ballast resistor for the aux. fan and picked up a new aux. fan switch socket (figured I'd replace it while I was doing A/C maintenance). I have plans to replace them this weekend. Anyway, the mechanic that did the recharge just informed me that it did not solve the problem. So, he took a peek at the compressor and noticed that the clutches were not engaging. The mechanic suggested that it could possibly be an electric problem. But wasn't sure... He mentioned that the A/C fuse was good, and that he did not know if there was anything else electrically that could be preventing the clutches from working. He indicated that it could possibly be related to the A/C switch mounted in the dash??? Any advise would be really appreciated.

[NoSpeedLimits]

Not being very familiar with A/C systems, I hate to ask but I gotta satisfy my curiosity...how can the system be out of refrigerant? I thought recharging an A/C system did ensure the system was full of new refrigerant? I didn't specify originally because I always feel that I am giving too many unnecessary details, but the mechanic told me that he drained the system and then refilled the system. Is recharging something totally unrelated to the refrigerant?

And after I borrow my buddies volt meter, where would a A/C ignorant person look to find the switch wire?? Or better yet, were should I tell my mechanic to check. Digital photos would be a nice touch...

Thanks for your help.

[DanDombrowski]

If I'm not mistaken, its the green wire in this picture. If its not, there should be only one wire going to the A/C compressor.

Recharging the system will fill it, yes. If it has a leak, however, the system can empty rather quickly. As far as checking to see if the system has refrigerant, the shop you go to will have no problem doing that, usually for free.

I'm not saying that because it doesn't come on its empty, I'm saying that if its empty, it won't come on.

I just did this troubleshooting on my Dad's Honda where they told him he had to pay a lot of $$ for an electrical diagnosis. A quick check of that wire revealed power to the compressor clutch, so we knew to look elsewhere. I doubt that testing the wire will give you a solution to your problem, but it WILL tell you if the problem is electrical or mechanical, and that will help a lot.

Since you said you're not that familiar with A/C systems, I guess I should add that the car needs to be running with the A/C on for you to check power to the wire.

Not being very familiar with A/C systems, I hate to ask but I gotta satisfy my curiosity...how can the system be out of refrigerant? I thought recharging an A/C system did ensure the system was full of new refrigerant? I didn't specify originally because I always feel that I am giving too many unnecessary details, but the mechanic told me that he drained the system and then refilled the system. Is recharging something totally unrelated to the refrigerant?

And after I borrow my buddies volt meter, where would a A/C ignorant person look to find the switch wire?? Or better yet, were should I tell my mechanic to check. Digital photos would be a nice touch...

Thanks for your help.

[NoSpeedLimits]

Thanks, and nice picture! My mechanic was asking about the location of a low pressure switch. He claimed most cars have one so that you can check to see if the refrigerant is low. So, does my car have one and if so, where can I tell him to look.

Also...I am afraid to ask for fear that the answer will result in an expensive repair. But, since today is pay day, I figured I better know if I should start saving. If there is power at the compressor, then as you indicate there is probably a mechanic problem...what kind? And, does it automatically mean the compressor needs replacement?

[DanDombrowski]

Not sure what to tell you about the low pressure switch, the most I've ever gotten into A/C work is buying that gauge thingy at wal-mart, hooking it up, and seeing if the needle is in the green, yellow, or red range, thats the only method I'm aware of to test to see if the system is full.

As far as the compressor needing replacement, its certainly possible at that age, but I wouldn't declare that the problem just because it isn't turning on. The problem could be as simple as a small leak in a hose thats causing the refrigerant to leak out, or it could be a bad compressor, you're just going to have to run through the steps of troubleshooting it.

Now I'm going to give you some hints on how you can test a few things in your A/C cheaply and by yourself, but remember, the system can build up some pretty high pressures if you're not careful, so don't say I didn't warn you. Fortunately, since you have a 94, you should have the R134a system. Better check that to be sure before doing any of this, or you could just have your mechanic do it, in any event, here is how to analyze what you have.

You can go to wallymart and get a can of R134a refrigerant with the reuseable filling system (tube, connections, and gauge) for about $20. If you can, get one where the can has the UV dye in it. If not, it might be another $4 or so. So you want to read all the directions and connect the gauge to the low pressure side of the system at the connections I mentioned earlier. Check a bentley to be sure. Now, this should tell you if the system is low or not. If its low, you can fill the system back to normal. This is actually a pretty common DIY procedure and is a good skill to have for pretty much every car.

Here's where you get into the analysis:

Was it empty (or too low a pressure)? If yes, you probably have a leak since you said the mech just filled it.

Does the system turn on when its filled? If yes, again, you probably have a leak, and the low level of refrigerant is what is causing the compressor not to turn on.

How long does the A/C work for if it does come on? 1 hour? 1 day? 4 days? This will tell you how fast of a leak you have, if you have one.

Now lets assume it was low. You've filled the system and the A/C comes on and blows cold. By tomorrow, its warm again. Now is when you take a UV light, like a blacklight (I think) and look in the engine bay for the glowing residue of the UV dye in the can of refrigerant you bought. This should help you find your leak, if you have one.

Now lets assume that the system ISNT low. If the system has a decent amount of charge and you have power to the compressor and its not turning on, this is where my experience runs out, I'm sorry to say. If I were to venture a guess, I would say a bad compressor. This is where some of the professional mechanics can offer some suggestions.

Even if you don't like to do a lot of work on your car, for about $25 you can gain a lot of experience about A/Cs work, and can save you a lot of professional troubleshooting. These are the same instructions I gave my father (a civil engineer, or as we mechanicals call them, the engineers that work on stuff standing still), who knows nothing about cars, and we found the leak pretty easily. Just be sure not to connect to the high pressure side and not to overfill and you should be safe.

Whew. Am I done yet? Anything I missed?

[NoSpeedLimits]

First, thanks for your time and the detailed response. Second, to give you an update. I questioned my mechanic about the systems pressure. He claimed that he checked the pressure prior to draining and replacing and said that it was good. I am a bit confused as to why he replaced it when it was supposedly good??? I believe he mentioned something about doing it as a precaution. Does anyone have the recommended hi and low pressure numbers available??? I don't remember the numbers my mechanic rattled off but I would like to compare them the next time I see him. Otherwise, I checked the fuses and did not notice any bad ones, plus the horn worked fine. Unfortunately, I run out of time so I did not get a chance to test for power at the compressor. Hopefully, I will fine the time on my next visit to the shop. And, I also want to question him on how he filled the system without the compressor running.

[Tiger]

Low Pressure is 34 PSI for optimal... 30 is fine also for colder A/C

[sbcncsu]

I am picking my car up this evening after the shop is done putting the finishing touches on my new paint job. Yippy!!! Obviously, I am going to want to show her off. Hence, my dilemma... Prior to dropping her off I learned that my A/C was not working properly - only blowing hot air. And since it 90 degrees outside, I need help. I had asked some questions on this forum last month, http://www.bimmer.info/forum/showthr...light=a%2Fcand and based on the responses the first thing I decided to do was have the A/C system recharged. Consequently, I found out that my auxiliary fan was not working. So, I bought the replacement ballast resistor for the aux. fan and picked up a new aux. fan switch socket (figured I'd replace it while I was doing A/C maintenance). I have plans to replace them this weekend. Anyway, the mechanic that did the recharge just informed me that it did not solve the problem. So, he took a peek at the compressor and noticed that the clutches were not engaging. The mechanic suggested that it could possibly be an electric problem. But wasn't sure... He mentioned that the A/C fuse was good, and that he did not know if there was anything else electrically that could be preventing the clutches from working. He indicated that it could possibly be related to the A/C switch mounted in the dash??? Any advise would be really appreciated.

Maybe this is too obvious:

How did he recharge it if the compressor wouldn't engage?
How could he read the high and low side pressures without the compressor running?

Answer: He couldn't have.

The low pressure switch is probably not making due to the low refrigerant. To check, simply jumper it with a paperclip. It should be located on top of the receiver dryer (I am not sure, I no longer have my e34 so don't quote me on that). If it isn't there, it will definitely be in-line somewhere on the low side of the system.

Good luck,

I hate A/C work....

[DanDombrowski]

Scott is probably correct about it being somewhere near the receiver dryer, that is where it is on my Volvo, however, I was hesitant to suggest jumpering this if the system is low because I honestly don't know what kind of damage it could cause to the system, running it without refrigerant (and thus running without lubrication). Perhaps it will be perfectly fine, but I don't know, and now I'm asking.

Now, as far as charging it without the compressor running:

If he's a competant mechanic, and I'm going to assume he is, we'll say he's using all the proper tools and methods for filling the system at the low pressure side. If you start to flow high pressure R134a in from a can or resivoir or something, the pressure will increase until the switch does make contact and the compressor starts and the refrigerant flows through the system, allowing further filling. If it doesn't, well, I don't know what would happen, and I don't really want to either.

Am I wrong in assuming this is a normal procedure for filling a system that is too low to allow the compressor to come on?

Maybe this is too obvious:

How did he recharge it if the compressor wouldn't engage?
How could he read the high and low side pressures without the compressor running?

Answer: He couldn't have.

The low pressure switch is probably not making due to the low refrigerant. To check, simply jumper it with a paperclip. It should be located on top of the receiver dryer (I am not sure, I no longer have my e34 so don't quote me on that). If it isn't there, it will definitely be in-line somewhere on the low side of the system.

Good luck,

I hate A/C work....