1993 300D Getting Ready to Help on AC Issue - PeachParts Mercedes-Benz Forum

meltedpanda · #1 04-14-2006, 02:26 PM

My friends 93 300D stopped blowing cold air. Is this an R4 or R12 system.
If it is compressor, easy or hard to DIY
Other common causes?

Thanks

jcyuhn · #2 04-14-2006, 05:53 PM

It's factory R-134a.

Compressor R&R is reasonably easy on this car. Wouldn't bet on that being the problem. Most likely issue on a car this age is refrigerant leaks. Too many possibilities to list there.

- JimY

rhodes2010 · #3 04-14-2006, 07:31 PM

Check to see if the compressor clutch is engaging, and that the
compressor is indeed running.

The belt can spin, and the middle part of the pulley will not be spinning.

This can happen if the freon/refrigerant is too low.

Is the blower motor in side the cabin blowing air at all ?

If the compressor is spinning and the blower motor is not
you may just need to tune up the blower motor.

Have not really heard of problems with the vents opening.
Seems to be usually the compressor or blower motor.

meltedpanda · #4 04-15-2006, 10:16 AM

ACC units functions fine, clutch is not engaging at all, I guess it cold be very low on refergerant as indicated by 2010. Is there a way to put a pressure gauge on it to see, or otherwise to see if in fact that is the issue.
Thanks

jcyuhn · #5 04-15-2006, 03:50 PM

It has fittings for a standard R-134a guage set. Low side is up high on the drivers' fenderwell, just in front of the forward firewall. High side is down near the front of the compressor, near the condenser and fan belt. Can't really get them wrong, as high and low side are different...

As a quick and dirty test you can try jumpering the low pressure switch on the dryer. If the compressor starts, it is an indication the system is too low on refrigerant to operate. If forget which one of the two switches on the dryer is the low pressure switch. But if the electric fans on the condensor start up when you test it; then it's the other one...

- JimY

Ron in SC · #6 04-16-2006, 07:12 AM

Quote:

Other common causes?

Possible leak in evaporator. Might want to add dye and freon. Drive it and try to find leaks if any. If after 1 week or so the compressor will not kick on because not enough freon you will know you have a pretty bad leak which you will have to locate.

Also if the system is empty of freon you could pull a vacuum on the system and see if it holds. If it doesn't you'll know you have a leak but you'll still have to locate the source.

Arthur Dalton · #7 04-16-2006, 10:14 AM

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This will verify a leak , but is not recommended if unit has no refrigerant left.......
If you find there is no refrigerant, you already know you have a leak, so putting it into a vac will only cause the outside air/humidity to be sucked into the system via that same leak point..... not good.
When one has a leak , the system finally reaches zero standing pressure, but does no go into a vac .
However , the mentioned vac holding test is a technique for testing AFTER the leak has been found /repaired , before recharge to verify repair. This save the hazzle of recharging only to find the leak repair has not been successful................

meltedpanda · #8 04-16-2006, 09:44 PM

thanks guys, will do
What should the pressure be?

meltedpanda · #9 04-27-2006, 02:14 PM

well it would not take a charge, Any ideas?

skiier3_9 · #10 04-27-2006, 04:24 PM

what do you mean "it would not take a charge" -- you may have to jump the low refidg. sw. if this is indeed the reason that the compressor is not engaging -- others here will know better than I, what you should do (LarryBible?)

I would def. take pressure readings (with the car on and the ACC set at max cool) and post them

See this post for correct pressures:

http://www.peachparts.com/shopforum/showthread.php?t=150971&highlight=r134+pressure+chart

You should be charging the system on the low side (and I would be using a R134 with UV dye)

meltedpanda · #11 04-28-2006, 09:41 PM

thanks, will do some more homework