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  #1  
Old 05-28-2001, 07:03 PM
Johnson Chan
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Hello, this is for the 1992 300D 2.5

The AC blows hot/warm air. It uses R12 and I dont want to do a conversion to R134a if possible.

1) I had the system recharged with R12, and there are little to no bubbles through the sight glass. But still it blows warm/hot air.

2) The auxillary fans are not coming on in 70 degree weather. So I jumped the switch (which theoretically turns them on), but still they dont come on.

3) I checked the fuse box, all fuses have no problems.

4) the pushbutton unit works OK. defrost, min, max, heat, etc. works.

5) Last year when this happened, when I clean the engine using high pressure wash, it would fix itself, but this time, I wasnt so lucky. I would guess the cleaning worked by getting the grease, oil, etc. off the ac clutch, so far it seems clean.

6) How do you know if the compressor is working, am I supposed to hear it or something? The belts dont seem to be loose or have slack.

Im at a loss, so whats next? Thanks in advance.
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  #2  
Old 05-28-2001, 08:01 PM
MikeTangas's Avatar
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6) How do you know if the compressor is working, am I supposed to hear it or something? The belts dont seem to be loose or have slack.

JC,

Turn the key to run, one position short of starting, that'll get you the required juice. Then with the engine off, turn on the A/C (or have an assistant do it while you stand at the front of the engine). You should hear a solid clunk as the A/C clutch engages. If you know where the compressor sits and can see it, you can also watch the clutch action. If no clunk or clutch movement it could be an electrical problem or a bad clutch. If it makes the sound or you can see it engage try it with the engine running.

Once the engine is running you won't be able to hear it, but if you can see the compressor you can watch it. Does it stay engaged?

Just trying to give you a starting point.
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'73 280SEL 4.5 (9/72)- RIP
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  #3  
Old 05-28-2001, 08:47 PM
Johnson Chan
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Hello Mike,

I tried it and the ac clutch/compressor unit, I cannot see any movement.

When we turned the car to acc and turned the a/c on, we did hear the blower motor and glow plug relay click, etc.

I did not see or hear any movment from the ac clutch. But when I start the car, I can see it spin.

Anything else I should be checking for or how should I narrow this down more?

I was looking at fault code testing equipment, it would cost me $400.00 to buy this thing and use it once on the a/c, any thoughts?
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  #4  
Old 05-28-2001, 09:32 PM
MikeTangas's Avatar
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JC,

If the clutch isn't engaging then there is either an electrical problem preventing it from engaging, the clutch itself is bad or the freon is low. You said the system had been recharged, how long ago and was it by an A/C Tech?

Try doing a search, the procedure for jumping the clutch for diagnostic purposes was discussed not too long back.
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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.
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  #5  
Old 05-29-2001, 01:26 AM
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On your model the A/C clutch cannot engage without the engine running. The Klima relay deactivates the clutch when the engine rpm falls below a preset level.
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  #6  
Old 05-29-2001, 03:55 PM
Johnson Chan
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Jgl1,

Thanks for the tip, what about the auxillary fans? they have not been coming on lately and I tired to jump the switch but it still doesnt come on in the acc position.
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  #7  
Old 05-29-2001, 11:07 PM
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Dang jgl1, you mean I'm gonna hafta learn about more electronic gizmos if I ever get a newer model . Learn sumptin new every day.
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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.
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  #8  
Old 05-30-2001, 07:59 PM
Johnson Chan
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Hello Guys,

I checked the AC compressor. I saw the AC clutch engage when the AC is on and when I turn it off, the AC clutch goes off. So I dont see a problem in that reguards.

I also checked all the fuses they are OK.

Is it possible the AC system got "clogged" and needs to be flushed, if so how do you do that?

BTW, I will change to R134a, I ordered all the parts already for $116.00.

Thanks, I will appreciate any ideas on the subject....
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  #9  
Old 06-01-2001, 06:01 AM
Joe Mc
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a/c

Please checkout this site concerning a/c system. Saabmaster@Townsend.com. Click on Saabmaster, then enter, then climate control. Good info about do's and don'ts on a/c system concerning converting to r134a.
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  #10  
Old 06-01-2001, 06:20 AM
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Join Date: May 1999
Location: Charlotte, NC, USA
Posts: 688
AC compressor problems...

It may be that the reason you don't see any bubbles in the sight glass is that the freon is not passing which can be caused by different problems. One may be that the expansion valve is plugged up or the compressor has defective reed valves in it. The fans won't come on until you build up enough head pressure, not when the compressor starts. If you jumper the pigtails on the drier then the fans will run.
Check the compressor by putting gauges on the high and low side or see a competent AC tech.

TobiasMB
4 MBs
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  #11  
Old 06-01-2001, 07:43 AM
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Join Date: Aug 2000
Posts: 269
If you don't have a set of AC gauges, look at the sight glass with the engine running and the AC off, then have a friend turn the AC on you should see a rush of bubbles as the compressor engages and then it should turn clear. If the clutch engages and does not cycle you likely have freon still in the system. Check to make sure your momo valve is working to turn off hot water going to the heater core and that the recirulation flap (behind the glove box) is opening fully (closing off outside air)

Bob D.
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