12 volts where are you?

[b_train_98]

I didn't realized I wasn't in the a/c forum until it was a little late. I'm not having any luck what so ever getting 12volts to my compressor. I tested the diodes (700-800mv), tested the relay (don't remember numbers), replaced accumulator because of a small leak, replaced the low pressure switch. Theres a connector in front of the accumulator (4-pin), I was only getting 12volts in to it and not out. I replaced the connector and still only get 12v into it. I pulled the relay out today and I'm not getting 12v into the relay connection in the fuse box. The relay next to it (heater/blower motor?) has 12v on all the connections. What am I missing? Getting desperate as it's getting real hot now!
http://www.explorerforum.com/forums/showthread.php?t=216560

 

[BrooklynBay]

Do you have a schematic diagram? Did you ever check the control on the dashboard?

 

[b_train_98]

weery wiring?

I did finally find a schematic for my 93 explorer. I haven't tested that switch with my meter yet. Looking at the diagram, it looks like power should get through to the a/c system when the light is illuminated and I DO see the light. Pulling that unit out would take a bit of time, might have to wait unit Tuesday. Any other ideas in the mean time? hopefully one that will find the problem!

 

[b_train_98]

12v in the dash

I pulled everything apart yesterday. I have 12v into the switch on the dash and 9v at the 10amp fuse under the steering. I shouldn't be getting 12v to the compressor without a charge in the system. I know I wasn't getting 12v before I replaced the accumulator (that's the whole issue) and have NOT charged it yet. How would I test it without a charge? I don't want to charge it up then realize I have to replace something and spend more money to charge it. I've already spent $200 trying to get this fixed. What about jumping the switch and starting the truck to see if the compressor will start? If it does then I guess I can charge it and be cool! If not then the same problem would be there; no 12v at compressor.

 

[b_train_98]

While I'm attempting to figure this out I'll get some more parts. Where exactly is the orifice tube? Does a new accumulator come with oil, not sure if mine did. I haven't figured out why I'm not getting 12v into the relay. The relay tested good just can't get power to it when it's plugged in. All other relays still have power into the socket.

 

[b_train_98]

relay needs 12v

It's not automatic. Set the blower motor speed, turn on a/c and that's it. It doesn't automatically change temp or anything. I did find a thermal limiter in my diagram for the blower motor. Is that related to my a/c relay not getting power? The diagrams don't show anything else like that.

 

[Cobraguy]

Wait...you don't have a charge in the system?? If not, then you won't get 12V to the compressor! You must have a charge to close the low pressure switch and allow current to the compressor. This is there to prevent the compressor from running without a charge (and oil) and destroying itself. You can jump across the low pressure switch harness, but if you do that without a charge, kiss your compressor good bye. And then you have to take the entire system apart and flush it.

What do you want to test? For leaks? The only way you can test is to (a) put a vacuum on it and see it it holds (b) put a partial charge in the system and check for leaks with a leak detector. Since I doubt you have a vacuum pump and leak detector, this would require a trip to a shop. Do NOT just try and put Freon in it. The system needs to be evacuated first to remove moisture from the system. Especially since it's been open.

I'm not sure where the orifice tube is on a 1st gen. On 2nd gen, it is located in the evaporator core inlet. (bottom fitting) Since your system is empty, this should be removed and checked for debris. It will have some. Clean or replace. They are only a couple of bucks.

 

[b_train_98]

Sorry, I've posted to a few forums didn't realize I haven't updated this one. I have replaced some seals, accumulator, oil, orifice tube (debris on the first 2 screens on old one) I'm forgetting something. Then I charged it up by jumping the compressor. One can brought it up to 25psi while charging. When everything plugged in factory it got up to 100psi and still wasn't kicking in the compressor. I didn't have 12v coming into the relay before I charged (haven't checked after yet) so I thought maybe I have a thermal limiter stopping the power to the relay.

 

[b_train_98]

I was just playing around a little. My compressor has 3.6 ohms, relay has 14v while engine is running and the system is holding a charge of 25psi for at least a week. I brought it down from 100psi, I didn't want to blow anything up! Still doesn't want to kick in. I have 12v into the low pressure switch, tried jumping the switch and no luck. Still can't get 12v to the compressor.

 

[Cobraguy]

So without the compressor running, your pressure is at 25 psi?? Your system is empty and will not run. Static pressure on a 90 degree day will be something like 90 psi. When the compressor runs, you will normally see the low side in the 30's when engaged and the high side between 150 psi to 275 psi, depending on weather conditions.

Have you tried jumping across the low pressure cut out connector off the accumulator? I just can't follow what you're doing.

 

[b_train_98]

Yes I have jumped the low pressure cut off switch and it stills doesn't work. Are you saying I should charge it again with another can? How high of a charge can it handle without damage?

 

[BrooklynBay]

Jumping the low cut off switch should turn the system on regardless if there is a sufficient charge or not. There is another problem.

 

[b_train_98]

I realize that. The only reason I even touched my a/c is because I can't get 12v to the compressor. I've done allot of things and can't seem to figure it out. Thermal limiter? 93 Explorer

 

[Cobraguy]

If you've jumped the low cut out switch and nothing happens, I wouldn't charge it again until I could get the compressor to engage. Brooklyn is correct...jumping that connector will engage the compressor regardless of the amount of Freon in the system. Do you have the factory wiring diagram? That's where to start. Follow it completely and see where you lose your voltage. I have a "tone" generator I can use in this situation in case there is a break inside a harness somewhere. I can find it that way. If you don't have access to one, then find the component you lose the signal and run a temporary jumper to the next component in the system and see if your problem goes away. If it does, replace the wire completely and don't worry about finding where the open short is. Just be sure to "retire" the wire.

 

[BrooklynBay]

Harbor Freight sells an inexpensive circuit tracer. I have a product review on it: http://www.explorerforum.com/reviewpost/showproduct.php/product/285/cat/500

 

[b_train_98]

Awhile ago I found something interesting. There is a 4 wire connector in front of the accumulator, 2 wires to the low pressure switch and 2 wires to the compressor. I have 12v into the wires that go to the switch. I DON"T have 12v in the 2 wires going to the compressor (I get the same voltage at the compressor 0.01v). I cut that connector out and used new connections, taped the hell out of it. How can I test that wire with a multi-meter? I tested a spare wire once but got the same numbers so I'm not sure if I'm doing it right.

 

[b_train_98]

it's fixed!

I think it was a combination of things. The only thing I didn't test was cleaning up a ground wire behind (toward the firewall) the fuse box under the hood. I took it to a shop and all they really did was charge it a little and it worked fine. It must have been the ground wire. Is that where the ground is for a/c?