Engine Size: 3.5L
Refrigerant Type: 134A
Country of Origin: United States
Hope all is well. I've got my wifes compressor off and the new one ready to go on. They are identical with one small issue.
The old one (original with car) has a two pin plug. One wire is white and the other black.
The new one has a single pin connector. There are two wires coming from the clutch(both black). One goes to the connector, the other is grounded to the compressor case.
I thought it would be simple and that on the old one, that the black would be ground. When I check them with an Ohm meter, both wires are open. When I check both wires on the new one, they both appear to be shorted to ground (0 Ohms).
Can any one help?
Resistance thru the coil shoud be 3 to 4 ohms. If your meter is analog be sure to zero it first. The two-pin plug probably has one wire grounded thru the harness (double check this). So you can drive the new compressor from the one "live" wire in the plug and leave the other coil wire grounded to the frame. There should be 3 to 4 ohms between the 2 pins on the 2 pin compressor. If not the coil is bad.
That is it exactly! Thanks! I got 3.5 ohms across the coil. I also determined which wire from the vehicle is grounded. I'll retrofit the new compressoer so that I can still utilize the plug.
More problems that I hope you can help me with. I installed all my A/C components and went to vacuum out the system. My old Edwards lab vacuum pump worked for about 5 minutes and crapped out. I took it apart, and the diagnosis is that the electrical motor is gone. Even with the pump disconnected, the electrical motor barely turns.
Being Sunday, the only place where I could get one was Harbor Freight which had a cheap veturi style. After pumping for 45+ minutes I was able to get it to about 28.8 "hg. I followed the instructions on this site and let it sit for 15-20 minutes to make sure that the gauge didn't move. I hooked up a 12 oz can and only a few ounces at most went into the system. I started the car and jumpered the clutch to get the compressor turning. It seems like nothing is going in. The only readings I get are about 90psi on the low side and and 0 on the high side. After about 10-15 minutes I gave up.
Do you think it is the vacuum pump? What would your next step be. I think my next step will be to take it to a trained professional!
Edited: Sun July 13, 2008 at 1:29 PM by brucebotti
High side should never be lower than low side. I suspect that your high side hose coupler, and possibly the low side one as well, are not actually opening the valves in the car. Are they the kind where you have to turn the knob on the top to push the pin out?
If that's the case you still have a system full of air, you only evacuated and charged the gauge and the hose.
It should not be necessary to jumper anything to charge a system. Charge as much as you can as liquid with the engine off, then start the car and all the safeties should be satisfied so the compressor will run.
The motor on an Edwards pump should be a standard NEMA face mount (or perhaps metric standard), you can replace it with a generic motor. The pump half of the unit is the expensive part. Make sure your motor is wired for the proper voltage if it is a changeable type.
To check if your couplers are really engaged, open only the high side valve when you start to evacuate and watch if the low side gauge goes down into vacuum. This shows the vacuum is flowing through the car. Then open both valves and evacuate fully. Of course use a mechanical pump, the air one will not do a complete job.
Charging with liquid is exactly as you describe, it should take only seconds for the first can starting from vacuum.
Sounds like your replacement compressor is of the Japanese type, can find one side of the coil grounded to the case with a screw, that is where you want to put your existing ground wire with an eye terminal connected to the bare end.
You are also learning venturi type vacuum air compressor fired devices don't work, don't even know why they bother putting these things on the market, worthless.
I'm a tad older than you and my master just taught me how to sit, so even I can learn new tricks.
You didn't mention why you had to replace the old compressor, if it seized or just had a leak, the former is disastrous requiring a complete flush new accumulator, and perhaps even a new condenser, the latter leaves you into the dark as to exactly how much oil you have left in the system. Only way to be sure is to flush it and add the OE recommended amount. BVA-100 as sold on this sight is a good deal as it doesn't absorb moisture like PAG does. OE's pump this stuff in, air tight into a near perfect vacuum so they don't have that moisture concern, but not so easy to do this at home. With R-134a, always good to change the accumulator, kind of a one shot affair, once it gets wet, it's history.
Charging stations are nice, can leave the lo and hi side hoses connected and play with button to vacuum and charge, when you have to remove these hoses, the ports want to suck air like crazy when switching from vacuum to charging.
Hooking your pump to the blue hose, can to the yellow hose, and red to the high side, can leave the high side open, can valve closed, open the low side valve and let a good vacuum pump really suck it clean, close the low side, and open the can valve to get an initial charge in the system. That way, when changing or purging hoses a bit of refrigerant is leaking out rather than air leaking in. Air is some pretty bad stuff in an AC system.
For that first can, as long as the valve is open, can really heat the pants off of it, it will not explode, but you will get the last drop of refrigerant out of it, could set it in a pan of hot water or use a hair dryer.
With the oil, new accumulator, good vacuum, no air or moisture, that will let your system work for a nice long time which should also be apart of your goal.
Well, all's well that ends well. I finally finished up the recharge on my wife's 300M. I was actually done two weeks ago, but wanted to make sure it still held a charge before I started gloating.
Of course you guys were absolutely right and all I was doing was vacuuming and charging the hoses. After much frustration, I realized that the instructions for the quick-connect shutoff valves were wrong. They said to shutoff the valves, you turn them clockwise. In reality you turn them clockwise to open them. Harbor freight foiled me again. When I finally figured that out, it was easy. The book says 25oz of R134, but I was only able to put in 23 without the low side getting too high. The air coming out of the vents is a beautiful 40 degrees.
I want to give a big Thank You to all who helped me out. I'm glad I went out and bought a real vacuum pump. I took great pleasure in smahing the Harbor Freight venturi one. As promised, right after this thread I will make a $50 donation to the forum. It is a small price to pay for all the professional and quick advice that I received.
I still have the old Edwards lab pump with what seems to be a bad motor (electrical). Is it worth anything?
Bruce, thank you for the support donation! Glad the members could help with your a/c issues! nice to hear the success stories now and then!
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