Where to start in AC diagnosis? - PeachParts Mercedes-Benz Forum

dwoloz · #1 07-24-2007, 10:47 PM

83 240D (has manual controls, no CCU as far as I know)

Turn on the AC, no cold
To me it doesn't feel like the condensor ever gets engaged, I just don't feel any difference in the car from with AC on or off so I suspect it never really turns on.

Where do I start to diagnose?

tangofox007 · #2 07-24-2007, 11:39 PM

Quote:

Originally Posted by dwoloz

To me it doesn't feel like the condensor ever gets engaged

The condenser is already married, to the evaporator. Despite being complete opposites, they make a great couple.

It's the compressor that is known to break engagements.

dwoloz · #3 07-24-2007, 11:42 PM

Err, compressor is what I meant, sorry

I was mostly just trying to indicate that I am not feeling any indication from the car that when I switch on AC, it's actually switching on anything

tangofox007 · #4 07-25-2007, 01:59 AM

Then checking refrigerant pressure would be a good place to start. The compressor will not engage if the pressure is too low.

dwoloz · #5 07-25-2007, 02:44 AM

Is there a recommended gauge for this job?

Is the electrical circuit ever problematic or is it most likely a recharge that is needed?

Should I be worried about leaks or was this most likely just caused by old age?

rrgrassi · #6 07-25-2007, 10:32 AM

Quote:

Originally Posted by dwoloz

Is there a recommended gauge for this job?

Is the electrical circuit every problematic or is it most likely a recharge that is needed?

Should I be worried about leaks or was this most likely just caused by old age?

Manifold guages are what is required. If there is 0 pressure, all freon is gone. A recharge will show you where the leak is, but they system need to be evacuated, IE vacuumed, to remove moisture.

The electrical can be problematic, but you are better off checking the simple stuff first.

spugeddy · #7 07-25-2007, 11:53 AM

I am contemplating taking mine to a local reputable guy.

My brother took his car to him and they charged, found a leak, repaired, re-charged for $100 bucks. Car was 95 Ford Explorer.

Is it, in your opinion, worth taking it for this type of service, or is this AC system too complicated, or foreign (not a pun) for some hayseed to work on.....

rrgrassi · #8 07-25-2007, 11:59 AM

Actually the A/C system is easy to work on, except for the vacuum pods in the dash. Everything else is easily accessable, except the high side port. Just be careful where you take it, as you can find parts online for half of what you can get them for OTC. Compressors prices are similar though.

tangofox007 · #9 07-25-2007, 12:28 PM

Quote:

Originally Posted by spugeddy

Is it, in your opinion, worth taking it for this type of service, or is this AC system too complicated, or foreign (not a pun) for some hayseed to work on.....

The refrigeration portion of the system is not foreign at all!! It's GM. Even the fittings are SAE.

dwoloz · #10 07-25-2007, 01:28 PM

Quote:

Originally Posted by rrgrassi

Actually the A/C system is easy to work on, except for the vacuum pods in the dash. Everything else is easily accessable, except the high side port. Just be careful where you take it, as you can find parts online for half of what you can get them for OTC. Compressors prices are similar though.

Isn't there a special recharge machine AC shops use to vacuum the old stuff and put in new?

I don't think I'm equipped for this job unfortunately

rrgrassi · #11 07-25-2007, 01:56 PM

Quote:

Originally Posted by dwoloz

Isn't there a special recharge machine AC shops use to vacuum the old stuff and put in new?

I don't think I'm equipped for this job unfortunately

You can "Borrow" a vacuum pump from AutoZone with a deposit. What you are thinking of is a freon collector. They do have machines that house a 30 lb. canister of freon for charging, and some also have the combo machines that do it all. You need to decide if you want to use R12 or R134a. R12 you can do yourself if you still have cans laying around, and 134a you can buy at the store.

They charge a lot of cash to do that sort of thing, but you are mainly paying for labor and use of the machines, which are a huge investment for any shop.

I prefer to DIY since it saves me a ton o'cash. I borrowed a vacuum pump from a friend and a flushgun from another friend. The rest I bought, or already had (guages, methanol for flushing, and all the parts).