Why? Jumpwire between A/C and Alternator?
 

Okay, so I've been searching for a week to find a short/parasitic draw that kept draining my battery (I'm new at this - took me a few days to figure out how to even search for it). And I finally found it - there was a jump wire between the wire that plugs into the A/C compressor and the alternator.

So here's the story - I bought the car about 6 weeks ago. Prior to buying it, I asked the seller to charge the A/C system, since he said as far as he knew, it was just out of refrigerant. So he had it charged. A/C worked great, but the compressor ran all the time - even with the A/C switch (on the dash) turned off. Even with the fan blower turned off. After a few days, all the refrigerant was gone, and it no longer cooled.

So my question is, why would you run a jump wire between the A/C and the alternator? I understand that this will cause the A/C compressor to run all the time, but why would you need to do that? I just don't understand. I suspect they did it when they replaced the refrigerant, but just not sure of the purpose in doing that.

Any help? Before you flame me, I would search the archives but I don't even know what to search for.

Thanks for the help.

maybe the a/c switch doesnt actually work and he wanted you to think the a/c was fine so that he could sell the car. Or maybe the thermal switch was mal functioning or something and did it for the same reasons i just listed

Yeah, there is a definite problem with your AC system. All he did was band-aid it to work.... just to make you happy... so you would sign papers.

It sounds like there are two problems:

a leak in your system somewhere (or he had it filled with the wrong refrigerant)

and and electrical gremlin... which happen to be semi-prominent in FDs.

Maybe he wanted the fans permanently on full blast to keep the engine from overheating.

thewird

Does your car have R-12 or R-134? If you have the latter, I would just charge it up with a $10 charging kit that you can buy from a local auto store.

Then, remove the jumper wire and see if it works properly. If not - as the previous poster mentioned - you have other issues in addition to the leak. It could be the AC switch in the dash, the AC thermoswitch attached to the evaporator, or the pressure switch next to the drier, or something else... There is a very good set of diagnostic procedures in the Body Electrical Manual (which can be found in the stickies).

Oh yes, and email the previous owner and tell him that he is a scuzzball.

Thanks. I took off the wire, and the A/C appears to work properly so far, in that when I press the switch on the dash, the compressor kicks in, and when I press it again, the compressor cuts off. It still doesn't have refrigerant, so I don't know if it works properly when charged. As for R-12 vs R-134, I'm not sure. How do I tell which one it has? Is that something that's listed in the owner's manual? I trust the seller - he was completely honest about every other thing on the car. I suspect his mechanic who charged the AC is the scuzzball. Unfortunately, that mechanic is 100 miles from me, and not worth pursuing.

Thanks for the help.

You've probably got a first class mess on your hands.

I'm guessing that the system was totally empty when they decided it was time to charge it up. If the system is totally empty, the low pressure cutoff switch will prevent the compressor from running. The proper thing to do in this situation is to pull a vacuum on the system and then charge into the vacuum. That will put enough refrigerant in the system to allow the compressor to run semi-normally.

I suspect they didn't feel like pulling a proper vacuum, and just hotwired the compressor so they could dump some gas in there and get semi decent cooling.

What year is the car? If it is a 1993, then it is a factory R-12 system....of course there's no telling what's been done to the system since it left the factory. Somebody may have converted the system to R-134a using the proper techniques and procedures, or somebody could've used a death kit on it from the auto parts store which will probably kill the compressor after a summer or two. On the other hand, if it is a 1995 car then you have factory R-134a. If it is a 1994 then you could have R-12 or R-134a. Look under the hood for a sticker that shows what type of refrigerant and how much. Then look over at the high/low service ports to see if they're R-12 fittings or R-134a fittings.

If you want a properly working system that will run reliably for years to come then you need to either take it to a shop that specializes in A/C repair and prepare to spend some $$ or you need to plan on investing some time in learning how to fix A/C systems and you'll need about $250 worth of tools plus who knows how much in parts to do the job right.

Thanks. I'm taking it to a dedicated automotive A/C shop on Tuesday. I'm hoping the system isn't all jacked up. I guess I'll know more after they look at it. It's somewhat reassuring to me that the day after it the system was charged it blew air so cold that I had to roll the windows down to let in some warm air. And also that the compressor does actually come on when I press the dash button and go off when I press it again. Hopefully the jump wire was just due to a lazy tech and not a defective system.

Oh, it's a '94.

Thanks again for the help.

With a '94, there's hope. If it was factory R-134a then you don't have to worry about some goons mucking about with a half assed conversion. Best case scenario is that you've got a leaking o-ring in an easily accessible location and all it will need is an o-ring, new drier and a recharge. Let us know how it turns out.

I'll let you know. i looked under the hood, and it's R-12. I don't think it's been converted, but not really sure. The receipt from the "mechanic" that charged it says they put R-12 in it. I hope it's something simple.

Just an update. I took it to a reputable AC shop. They found the leak in one of the hoses and replaced it. They also replaced the dryer since it had never been replaced. As far as they could tell, the jump wire didn't do any damage and the system works fine now. Total cost was just under $500 and it cools like a champ.

Thanks for everyone's input.

That's not too terribly bad as far as cost is concerned. Where'd they get the hose from? Supposedly all the hoses are NLA from Mazda. I suppose they could've taken the two metal end pieces and put a new piece of hose between.....

Glad to hear you got her up and running right!

Not sure where they got the hose from. All they do is AC work, so I suppose they could have manufactured their own.