After spending a cool $700.00 to get the wife's AC fixed on Friday, I need a little help with my car. The car in question is my 87 300D. The AC just isn't blowing cold anymore. I have absolutely no idea how to troubleshoot an AC system. I could take the shotgun approach and replace everything, but it would cost as much as putting it in the shop for the pro's to figure out. Is there a clear cut method to figure out what is wrong with my AC? I need to figure this one out pretty quick since it is starting to heat up here in Houston an the car is black with black interior...some would call me stupid for buying a car of this color in Houston.

Thanks for any help.
Mike

__________________
Mike

'80 300D
'84 300D
'85 300D
'87 300D

The best way to check the system would be to put gauges on it to check the charge. You could check the whole system for leaks. Use soapy water in a spray bottle or look for oil leaks. Gauges would be more accurate though.
Make sure you check the expansion valve located under drivers side dash panel (under stearing wheel). It's way back against the firewall. Has 2 lines going in and 2 coming out. The O rings tend to leak sometimes.

Also, if you don't have access to R-12 you could consider changing over to 134A.

As with any repair you need the correct tools.

Danny

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

Do you know if the Compressor Clutch is actually engaging?
On my SDL the Clutch & Aux. Water Pump are fed from the same fuse and if your Water Pump is seized (quite common) the fuse will blow and the A/C will not operate. Check your fuses (on the SDL it is #5 - maybe different on a 300D) first and then make sure that the clutch is engaging before troubleshooting the rest of the A/C system

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

sublettm,

Short the terminals on the pressure switch, usually located on the dryer. If you hear the clutch kick in, you probably lost freon charge thru a leak. Don't keep the short connected any longer than you need to test the clutch and make sure the AC is set to cool.

P E H

Thanks for the help guys. I now have something to do when I get home tonight. I'll keep you posted on what I find.

Mike

__________________
Mike

'80 300D
'84 300D
'85 300D
'87 300D

Mike, You have not posted much...but you have been a member through Two Summers.... which included the AC wars......
There is all sorts of good stuff in our archives concerning checking, flushing, filling, replacing stuff.... I suspect you had a good AC during that time and did not read them (?) .... but they are still there available with a search...

Yeah discussions about R12 vs. R134 are about as common as the dreaded oil threads. Now about the 134 conversion.....

__________________
LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

We have an '87 300 D Turbo, and the AC was doing almost exactly the same as you describe - no cooling. Here's the first thing to check: is your coolant charge good? You can tell by seeing if the A/C Compressor clutch cycles on when the temp knob is rotated full cold (on) then full hot (off). If it doesn't, have the coolant charge checked.

There are a whole lot of other things to start checking - look on the previous threads for some some thorough testing processes. One other thing - I'm guessing you do get full air volume through the vents, right? Sort of a silly question, but if the vents are not opening properly, you don't get any of the cooled air.

Our '87 went from lukewarm to really, really cold once the coolant was ok. It's running the R-134 (prevoius owner made the converstion) and works great.

Hal

'87 300 D Turbo at 289,000 miles
'98 E300 Turbo Diesel at 73,000 miles
'83 911SC at 105,000 miles and still the best driving car ever.