Is my AC compressor good or bad? - PeachParts Mercedes-Benz Forum

jfikentscher · #1 08-05-2003, 09:07 AM

Is there a way to easily check if my compressor is good/Bad or do I just need a charge?

About a year and a half ago the blower stopped working and I went through a summer without AC. This summer I fixed the blower but now the AC does not work. It was working great when the blower stopped.

This is on the 1987 300D.

Thanks,

Joe

jas2wa · #2 08-05-2003, 09:21 AM

Well, the quickest way to check it out is to engage the a/c system, check under the hood to see if the compressor is actually spinning with its belt still attached. If the belt is thrown, then the compressor is seized. If everything is in fact turning, but just not getting cool, then you have to have the system checked for leaks, repaired, and then re-charged.

If the compressor needs to be changed (along with the receiver/dryer- necessary to get warranty coverage on new compressor), make sure the whole system is flushed completely before re-charging. Otherwise, metal particles from your previous compressor will hasten the demise of the new one...

Hope this helps-

JAS

jfikentscher · #3 08-05-2003, 09:48 AM

The belt is one of those serpentime belts and is intact. It looks like the compressor is spinning but it doesn't sound like it is engaging.

Joe

jas2wa · #4 08-05-2003, 10:04 AM

So it is likely not seized, that's good. The clutch isn't engaging the compressor, though. Most likely, this is what's happening: when the system is low on refrigerant, in order to prevent the compressor from frying itself, it will not engage. On the later systems like yours, I think this is how they are designed.

Your best bet is to have the system charged to see what happens, most likely it will be fine. If it has a small leak, it will become less effective over time, at which point it will need to be leak-tested, repaired, then re-charged.

A/c is a pain when it doesn't work. Have had 2 123 chassis cars worth of a/c rebuilt. It gets into a bit of trial and error.

JAS

jfikentscher · #5 08-07-2003, 03:48 PM

Well I am being quoted $250-$300 to fill with R12. Does this sound too high?

Joe

PiP · #6 08-07-2003, 05:09 PM

Yes, that is too high by Texas standards.

Most local shops will do an AC check for $20.

They fill it with R12 and check for leaks.

At least then you will know if you have any leaks, and at about $50 a can, R12 isnt as expensive as it once was, but no use in being wasteful.

leathermang · #7 08-08-2003, 06:40 AM

Here is a new ' completed items' url for R12 on Ebay....

http://search-completed.ebay.com/search/search.dll?GetResult&krd=1&ht=1&sortproperty=metaendsort&query=r12&from=R8&completedonly=1

If you look at it you will see that 12 oz cans average in the LOW $20's....

Yes, you may need to get the $15-20 online open book 609 certification to get it shipped to you ( or have them ship it direct to your mechanic , who we assume has the cert already )......

but this is half what I see people quote for R12 all the time.... R12 would be worth it at the $50 per can... but the fact is one CAN get it for half that... so it really is worth using it in these old MB's.

#8 08-08-2003, 08:30 AM

With the symptoms you offer, you need to put gauges on and check the charge. Probably the most common cause of clutch not engaging is a low charge. There is a low pressure cutout switch that interrupts the clutch circuit in the case of a low charge to prevent compressor damage.

Start with gauges.

Good luck,

#9 08-09-2003, 11:51 AM

I have a similar problem. After the engine swap the past owner never charged the AC system. After I replaced my blower I charged it with a 134a conversion kit. The clutch wont engauge, and I suspect its electrical. I looked at my dryer (I think) and 2 of the wires coming off of it are disconnected. I tried connecting them but no change. I can't find a wiring diagram in any of the books or manuals. I know its properly charged and everything except the compressor is working as it should.

Ted2222 · #10 08-10-2003, 12:56 AM

The fact that your clutch won't engage may be a lucky break. If you will go to A/C Information Forum and do a search on "Death Kits", you will find that the professionals refer to those R-134 conversion kits as death kits. The reason being that there is a high probability of extensive damage to your entire a/c system when you use one of those kits. You may have the opportunity to get that stuff out of there before it does any damage.

If you didn't install a R-134 compatible receiver/dryer, the R-134 is likely to rupture the dessicant bag in the r-12 receiver dryer and it will end up contaminating everything in the system.

You say your system is properly charged. Do you have a set of manifold gauges to determine the system pressures? How did you fully charge the system without the compressor running? It can be done, but usually isn't.

I have the electrical diagram for my car and will try to assist you with that if you think it might help and are interested.

Good luck.

#11 08-10-2003, 02:50 PM

So, would I be better off going to a dealer or other benz place, getting the kit out of it and chucking $200 or so into it for R12?

I plan on keeping this car for about 5-6 years. Even in Colorado it gets fairly hot in the summer.

leathermang · #12 08-10-2003, 05:24 PM

Most of us don't have trust worthy places to take our cars... or can't afford the hourly charge of the good ones...
So we tend to suggest researching air conditioners/buying the tools ( which will last a lifetime if not abused) getting the certification ($20), buying the R12 direct cheap on EBay ( less than $100 for most cars).....
So really , if you have no leaks... your biggest investment is reading time in the service manuals and on this forum and on the AC forum ( aircondition.com) for instance...
If you can't trust yourself to do it RIGHT... then you are in BIG trouble...

Of course,,, you can do all this and then would be able to do a great job of supervising someone else actually doing the greasy hard parts...

Ted2222 · #13 08-10-2003, 09:42 PM

82-300td,

I sent you a private message. That is being posted here because, if you are like me, you would not find it otherwise.

#14 08-11-2003, 10:39 AM

Ted2222,
Thank you, I have never checked my private messages before. I guess I'll be checking alot more often.

jfikentscher · #15 08-11-2003, 01:27 PM

Hey Guys, How do I jump the pressure limit switch to run the compressor (1987 300D). They will need to do that if I have the r12 put in. I would like to see if the compressor is good before I continue.

Joe

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