The A/C relay AND the compressor clutchwere screwed up.

I just got back from the A/C shop. They do A/C systems for the Audi, BMW and Daimler Chrysler stealerships. The owner is really stuborn. He said "this problem won't beat me". So we drove around for about half an hour and the system was working fine. He put a thermometer to see how cold the air was and it is within spec.

Then I asked him to stop and put the car in neutral so we could look at the tachometer moving in accordance with the compressor engaging/disengaging. We started playing with the A/C on-off switch. After several times the compressor stopped engaging. Then we took the car back to the shop and tapped the compressor clutch with a long stick and it engaged, just like Tech said it would. We tried putting some compressed air in there to see if the mechanism was dirty, but it didn't change anything.

So next week after New Year Ihave an appointment at the shop to fix the compressor clutch. I will be printing Tech's tutorial and taking it to the shop next week so they follow Tech's instructions. Before that I am going to ask him how much he will charge me. Maybe I'll fix it myself. The problem is that I don't have jacks or access to an elevator so I can work under the car to remove the compressor.

As usual Tech was right. Thanks guy for the help, I'll post any news here.

 

Glad you finally got to the Root of the problem.

 

The guy working on it sounds very reasonable. I think I would pay him before doing it myself. Especially if he guarantees his work. A/C is one of the things I stay away from as far as doing it myself.

Good luck.

 

Labour is cheap here. I don't think they will charge me more than USD 100 to disassemble the compressor, fix the clutch and reassemble it all. I told him that Tech had quoted 4 hours for the whole job (not true) and he said that it was a reasonable time.

Volvo official shop charges U$ 30 / hour plus tax (21%) labour.I am expecting U$ 20/ hour from this Indy. He won't invoice it so I save the 21%. Yup, this is tax-evasion country.

 

I have just read another post by Tech, and this apparently can be done in 1.5 - 2 hours.

I'd like Tech to confirm that if I tap the clutch and the compressor engages then it's absolutely 100% certain that the clutch is bad. Is there another cause for this symptom? Sorry to ask so many questions, but I'm really low on cash right now and I want to be sure.

Regards

 

I just did an extra test, I unplugged the low pressure switch from the pressure line andshort-circuited the plug with a cable, just to make sure that it's not the low pressure switch that's "misbehaving".

With the a/c compressor engaged,I opened the wire and the compressor disengaged, as expected.

With the wire short-circuiting the sensor, it was still necessary to"help" the magnetic clutch to engage with a broom stick.

I'd like to do one more test, which would be to measure the signal voltage coming into the compressor that tells it to engage the clutch. I wasn't able to find that wire. Where on the compressor is that signal?

Regards

 

I'm not Tech by any means, but I would think that if you have to tap it with a broom stick to get it going that it is definitely the clutch.

 

Yeah, but if the magnetic clutch is faulty, then how come it sometimes works. The magnet obviously has enough juice to keep the clutch coupled. And when I put the A/C switch in OFF, the magnet releases the clutch immediately. Once it is engaged, the clutch does not slip. I'd just like to understand how the magnetic coupling process works, and why the gap is so important. Is it that the magnet is barely powerful enough to pull on the clutch, and if the gap is too big the magnetic field is too small to move it? Is that the problem basically?

 

Bump for Tech...

 

Yup. I had similar problems to you. I re-shimmed my clutch and everything is better. - AB

 

The Magnet overheats and releases the clutch due to the Excessive gap.
When it is excessive then it even has a hard tine engaging in the first place.

 

I did this test:
- engine off
- car is cold, hasn't been used for the last 2 hours. thus A/C clutch should be cold too.
- outside temp is 25C
- put ignition in ACC position, electricity is on
- put blower in minimum, temp in 16C, A/C on.
- short circuit the pressostat switch

The clutch should engage, but it doesn't. I put a metal stick close to the compressor and I can feel a very strong magnetic field. If I tap the clutch it engages.

Since the clutch is cold, I don't think the problem is temperature related. If you ask me, I'd guess the problem is with the magnet losing its magnetic power over time. I don't know if that makes any sense physically.

Another possibility is that the clutch mechansim, due to wear, is creating more resistance than it does when it is new, and it's having a hard time coupling. Maybe the axle on which it moves gets worn out and when you reduce the gap you are basically moving it closer on a differnt position on the axle, where it slides better.

Does this make any sense?

 

Hi Axel,

By now you seem to know about the A/C better than anyone.

My assumption is that the magnetic clutch is indeed losing power to couple. The clutch is electro-magnet, so I am assuming there is something that is causing voltage drop to the electro-magnet when the engine or the comp gets hot. I general, as the temp goes up, so does electrical resistance. But this is nothing but assumption so don't count on this. My 850's comp is made in Japan but could not identify the mfg. Usually, Japanese A/C components are reliable, as A/C is a must in Japan where it gets hideously hot & humid from late June till late September. Many Japanese auto mfg's use Denso or Keihin compressor (could be Mitsubishi or Hitachi as well).

I'm sorry I'm not much of use in this case.


JPN

 

Ok, my A/C shop opened again after two weeks of summer vacations and they reshimmed the clutch. When he opened the compressor they found the two washers, a thick one and a thin one. They just removed the thin one and left the thick washer in. The A/C guy said that he tested to see if the thin one would leave enough clearance for the clutch and it didn´t. There was risk of dirt getting in there and causing compressor disaster.

So the bill ended up being:
- Diagnosing and fixing faulty A/C relay:USD 50
- Clutch reshiming,full R1394 recharge, A/C oil recharge and pressure testUSD 110

They told me that removing the compressor was a major PITA. I guess they didn´t have the service manuals because I saw that Tech quoted 2 hours for that same job in another thread.

IMO I got a great deal. They also do injection so now I have a new injection shop too.

 

It is all working normally again though?

 

Apparently not. My wife says it's working better but it switches from on to off all the time. I guess there is another problem. Maybe the compressor is definitely screwed up, and it wasn't just the magnetic clutch?????

 

What does she have the fan speed setting at?
And temp setting?

 

We just went for an ice cream with the kids in the Volvo and I was able to test the A/C.

Outside temp is 30C, a very hot and humid night. The wind is barely blowing.

The clutch works perfectly, thank to your help Tech. I played with the AC on-off switch for about 40 seconds with the engine off and the hood openand it responded perfectly every single time.

Now in actual use, with both temp indicators in 16C (6 o'clock), the fan in auto,and the wind direction selector in "facial" or whatever that´s called, I could here that after a while the compressor was coupling and decoupling every 5-10 seconds. Obviously the air would get cold/hot/cold/hot.

The R1394a was charged last night, so I don´t think it´s low on freon. Maybe the compressor is screwed up definitely and there is some kind of overheating sensor being triggered. Then the compressor shuts off, the highway air at 70 mph cools it off a couple of degrees, the compressor temp is back in spec, then it gets hot again and so on.

There are two pressure sensors, right? I only changed one... so maybe the other one is the culprit.I'll bypass it with a wire to see what happens.

Maybe the faulty relay did not just have a bad ground. Maybe the relay itself is bad and that's why it is going on/off/on/off all the time.

I sure would appreciate more help here. I am pretty much sick and tired of this.I feel like putting a helmet on and totalling this crap against a illumination post on the highway to collect the insurance.

 

The low pressure switch might be bad.
Is the cooling fan working 100% properly?
How hot does the air get?

 

Hi Axel,

>I feel like putting a helmet on and totaling this crap against a illumination post on the highway to collect the insurance.

↑ (((( ；ﾟДﾟ))))

The two major defective designs on 850; A/C compressor & ABS module (Japanese & German).

I wonder if there is a compressor other than the OEM that can fit on 850. I bet a Denso compressor would perform a lot better. Maybe Volvo engineers didn't take the A/C design seriously, as the average temp in Sweden seems to be below 20C or something like that. But the OEM compressor is made in Japan, so some idiot in Japan may have screwed up the design. I'm ashamed.

Volvo's A/C set-up is beyond my ability at the moment, Honda's A/C is much simpler and a lot more reliable.

I'm sorry I am useless in this case.


JPN