How do you jump the A/C compressor to get it running?

[Brently]

N/m

[DBMaster]

Pull the pressure switch connector off the switch. It's on one of the lines connected to the receiver/drier. You can connect a jumper wire across the leads on the connector. Just don't run the compressor too long with no refrigerant/oil in your system.

[nswst8]

Why are you going to jump the low pressure switch? Reson being if you have to ask, you shouldn't being doing this.

I know that somewhere you heard that but its easier if you just have the pressures checked.

[DBMaster]

I have had to jump them in the past at times to get the compressor running when charging an empty system. Usually, once you have vacuum it will take enough charge to get the compressor going, but sometimes not. Either way, I was not indicating jumping the switch as something longer term than a few minutes.

[nswst8]

I have had to jump them in the past at times to get the compressor running when charging an empty system. Usually, once you have vacuum it will take enough charge to get the compressor going, but sometimes not. Either way, I was not indicating jumping the switch as something longer term than a few minutes.

No, Mike I was not trying to say that you were wrong in anyway with your help.

My reply in general was to the thread initial request. My advice to these guys wanting to check out their systems.

Jumping the compressor for you and I would be no problem. But for someone with little to no knowledge can equal a disaster.

[Brently]

Phil,

I feel your concern and Mike's 2nd response is what I would have said. I'm capable of messing something up and not getting pissed at anyone for giving me advice. However, I HATE electrical work because it's too much reading for me to learn. Everything else I can do.

Took the car to AC shop last week because I didn't have time to research and we've been having 100 degree days everyday. They checked system, filled with 134a and put in a dye. I drove to work and system didn't get cool at all. Figured I let it rest out of the sun then start over, same problem. Had a friend take it back to the repair shop after I called, they told her it had a leak. Therefore, I'm now suspicious of the shop after $140. I haven't found the dye leak yet and my guess is they want more money.

Read that manual over and over and didn't see how to jump the compressor. Which led to Mike answering my question. Hope that cleared it up some. If I "F" something up it's okay, but I refuse to let a shop rip me off.

Guess where I'll be first thing Monday morning?

Brently

[nswst8]

Hello Brently,

My apologies, Mike and I get alot of the "I want a quick fix" questions and sometimes it gets pretty mundain in my opinion.

I like helping and try to as much as possible.

I just beleive that the most effective way to is to check the pressures. And this is real simple.

Get a inexpensive set at the local auto parts store, you should be able to rent/barrow them.

"Engine off"

Connect Blue to low side (just in front of dizzy) Valve in closed position.
Connect red to high side ( passenger side fender next to headlight) Valve in closed position.

"Engine still off"

Now this is the really simple part the pressure you see should practical equal the ambient temperture outside. 80 degrees outside = 80 PSI. Should your pressure = lower PSI to outside temp then you have a low charge.

Now this is the best way for you to check your system. Jumping the low pressure switch is a good shadetree way of ensuring the compressor is operating but if there is no charge theres no oil to properly lube the compressor during operation.

When I jump a low pressure switch it is only for a few moments to see the compressor engage. And I do mean only a few monents.

Now, if you can give us alittle more information, like the fact that you had taken it to the shop we could have told you what to look for.

Type compressor, if you converted it. And what you have done so far.

So again, I do apologize.

What else can we help you with.

[Brently]

Phil,

I'll stop being the shade tree and go get the set to test. Don't apologize, you're doing the right thing. It's a Denso I converted to 134a 2 months ago. It ran great for awhile, then stopped so there must be a leak somewhere. Mechanic said he oiled and installed leak test, but I can't seem to find where it's leaking.

I'll come back and let you guys know what I find if I get to it today. This baby is running good now, AC would just make it even better before it goes to the new owner, if she wants it. Or I might sell it because I thought my wife could use it as a delivery car for her flower business. But no, now she wants a Honda Civic Wagon ('87-'91) and I found a nice one on Craigs.

Thanks

[nswst8]

One of the simplest ways to check for leaks is to look for oily residue at the joints, connections.

Oil mixes with the refrigerant so when it leaks the oil will adhear to the point of exit.

If it is a fresh leak its kind of like looking for the wet spot.

You can add a dye solution, real simple after checking low pressure (jumping low pressure switch) simply get a can of refrigerant with dye/oil premixed and add thru low side (valve in front of distributor).

Can in upright position (this is called a vapor charge) can tap valve open, engine running, jump low pressure switch and add entire contents of refrigerant can.

Use UV light and glasses to look for leak. Repair as nessasary

[nswst8]

If there are no visable leaks then a possibility is that you could have a leak in the evaporator or behind the condenser (between the condenser and the radiator) these are the only spots that are not visable.

When you converted, did you convert it yourself or did you have a shop do it? How much R134a?

[Brently]

Darn it, that could be why I have a smell of old urine when I use the "Fresh" air.

I did the shadetree conversion, yes you know it. didn't evacuate only installed 134a (10 ozs). I'm seeing my problems now. It should take 22oz, correct?

[DBMaster]

If you had any leaks that let out the old R12 then even more 134a will leak out. I am not about to start another alternative refrigerant thread, though. You system may have held adequate vacuum when the shop recharged it, but 134a's positive pressure is greater than the vacuum pump's negative pressure.

No offense taken, by the way. :)

[DBMaster]

Oh, and since R134a has smaller molecular size and does not carry oil the same way R12 does you can indeed have a leak and see no visible trace. The dye ought to help, though.

[nswst8]

Darn it, that could be why I have a smell of old urine when I use the "Fresh" air.

I did the shadetree conversion, yes you know it. didn't evacuate only installed 134a (10 ozs). I'm seeing my problems now. It should take 22oz, correct?

Yep, 22-24oz should have found your sweet spot. The conversion would have required a discharge(evacuation) of the old refrigerant and a vacuumed sytem prior to the charge of R134a.

Since R134a has a higher operating pressure and that to a positive pressure system (no vacuum)= over pressurized system creating a even greater strain on an older system to operate.

Guess we found the culprit.

[nswst8]

Oh, and since R134a has smaller molecular size and does not carry oil the same way R12 does you can indeed have a leak and see no visible trace. The dye ought to help, though.

Question Mike? Are you finding leaks w/o oil residue associated with the leak. Most of the time I find that the shadetree wannabes overpressurize the system resulting in serious leaks and I'm finding the leaks with oil residue but confirming with dye.