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no 12v at compressor? Pages: 12

b_train_98 on Sun June 29, 2008 10:49 PM User is offlineView users profile

Year: 93
Make: Ford
Model: Explorer
Engine Size: 4.0l
Refrigerant Type: R12
Country of Origin: Canada

Hope you guys don't mind helping a newbie. The Explorer forum I've been on for a few years suggested I come here for some help, maybe I stumped them?

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, have since checked all relays and get power to them all. Jumped the compressor to make sure it will work when I fix it. And of course I pulled ALL the fuse's to make sure they're not broken. Didn't do all of this in that order, did some tests as I thought of them or was suggested via the Explorer forum. What am I missing? Getting desperate as it's getting real hot now!

Chick on Sun June 29, 2008 10:53 PM User is offlineView users profile

You have to check if you're getting 12v to the cycling switch on the accumulator (I think it's there) it's the two wire switch. If you're getting 12v to there, then check further down the line, (between the cycling switch and compressor) if not, check for 12v being sent to it from your control head. may need to reset the computer if your not getting 12v to it. What was the original problem?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

b_train_98 on Sun June 29, 2008 11:30 PM User is offlineView users profile

I am getting 12v to the switch. There is 4 wires that make a connection just in front of the accumulator (near the bottom), I am getting 12v into it and NOT out to the compressor. I found that last week so I replaced the connection and still only get 12v in and less than a volt at the compressor. This is the original problem by the way; not getting 12v to the compressor. I'm not sure what you mean by the control head? The climate control inside the cab? If so then yes I pulled the dash apart today and I'm getting 12v in to the switch in the cab. I'm getting 9v (10amp fuse) into the fuse box inside the cab. Not getting power to the relay under the hood though.

Dougflas on Mon June 30, 2008 5:26 AM User is offline

email me have that schematic


dktv at aol dot com put schematic in subject area

b_train_98 on Mon June 30, 2008 8:20 PM User is offlineView users profile

I e-mailed the only schematic I have on my computer. The other two are in my books Chilton and Haynes.

b_train_98 on Mon June 30, 2008 9:30 PM User is offlineView users profile

I ended up talking to my dad and realized another problem. 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.

Chick on Mon June 30, 2008 9:42 PM User is offlineView users profile

Ahhh..Ok, you have 12v to the two wire switch, pull a deep vacuum, and then let the vacuum pull in as much refrigerant as it can. That will close the switch, same as jumping it, compressor should start on it's own then. Don't jump any of the four wires on the other switch though, but make sure the plug is on tight and no pins are bent, .. The switches need system pressure to operate..The ECM should send ground to the compressor relay, I don't have the wiring diagram in front of me, but thats how most do it...Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Dougflas on Mon June 30, 2008 10:35 PM User is offline

You may have a bad/open at the wide open throttle relay (WOT). I sent you a schematic.

b_train_98 on Mon June 30, 2008 11:07 PM User is offlineView users profile

At first glance it's allot better than the one I have. Out of curiosity, where did you get it? Looking at it now, should have time tomorrow to play.

b_train_98 on Mon June 30, 2008 11:58 PM User is offlineView users profile

I do know that I'm not getting power to the relay socket, (engine not running). The low pressure switch has 12v. How would I further test this? No power would mean an open circuit? Where would I even begin. Any idea where the ground would be for the relay?

mk378 on Tue July 01, 2008 12:10 AM User is offline

You can introduce some R-134a for leak testing before commiting to a charge of R-12. Do not run the compressor with the R-134a in the system. You could disconnect the clutch wire and see if 12v reaches there with pressure in the system.

b_train_98 on Wed July 02, 2008 10:50 PM User is offlineView users profile

I couldn't find a ground for the relay no idea what to look for next. All relays have 12v except the WOT a/c. I might jump the switch tomorrow and see it it will click on, no pressure though. I'm getting desperate. I'm getting some seals and an orifice tube tomorrow while I'm waiting. Not sure if my accumulator came with oil in it so I might get some of that to, what kind do I need for a R12 system?

Chick on Thu July 03, 2008 8:05 AM User is offlineView users profile

Your ECM sends ground to the relay once it determines the system has pressure, as MK378 suggested, you can pressurize the system (leave plug off compressor) to see that 12v gets to the compressor once it has pressure. Don't go probing to much when it comes to ECM's...Do it the simple way..Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Dougflas on Thu July 03, 2008 12:18 PM User is offline

When I have problems as you have, I plug the compressor plug and put a 12volt test lamp in its place. This way, the compressor clutch does not engage so I don't have to worry if the charge is low thus saving the compressor. When testing ECM signal paths, NEVER ground a circuit. Instead, use a standard diode (1n4007 or equilivent) to ground with the band toward ground.

b_train_98 on Tue July 08, 2008 12:41 AM User is offlineView users profile

I'm not sure I understand what your saying for testing. How would I do that with a multi-meter? I started to trace the wires from the a/c relay then ran short on time. All I found is that the wires go into another thicker bundle and goes all over. Anyone have a wiring diagram for the fuse box under the hood for a 93 Explorer Eddie B? I'd like to find the wire that should have the 12v on it and find the other end (hopefully). Also I tested a spare wire; connected one end to a 12v spare battery and my meter shows 0.06v, the same as at the compressor. I guess the wire under the hood is good. Is there a different test that I should be doing for the wire? I jumped the switch as well and still only 0.06v at compressor. I think I'll test a wire again, don't remember if I had the ground on the battery or not (I'm sure I did?)

mk378 on Tue July 08, 2008 1:11 AM User is offline

Note that, of course, the engine has to be running when you do these tests. The PCM will not engage the compresor unless the engine is running at a normal idle or cruising rpm.

Be real careful jumping stuff and energizing "spare wires," etc. it is quite possible to fry the PCM or other electronic component.

I would again encourage you to plug everything in stock except the compressor, and put about 75 psi pressure in the system, could use nitrogen or R-134a. It only takes a few ounces of refrigerant to do that. Then check if 12v is reaching the compressor with the engine running and the A/C on (but don't plug the compressor in).

When using R-12 it is essential to first check the system for leaks under pressure not just under vacuum. Leave the test charge in for a day or more. If the pressure doesn't fall you can assume there are no major leaks and it is safe to evacuate and charge with R-12.

Chick on Tue July 08, 2008 7:24 AM User is offlineView users profile

your system has a few safety devices that prevent 12v from getting to the compressor unless the system is charged, so as mk378 suggests, pressurize the system to see if you then get 12v to the compressor. It won't get there unless it sees pressure in the system period. You can check the compressor coil with an ohm meter for 3 to 4 ohms, but as far as 12v, you do need pressure in the system, and you won't risk frying your ECM by jumping wires that only use 5v reference.. Hope this helps..


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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

b_train_98 on Thu July 10, 2008 12:42 AM User is offlineView users profile

I had a hell of a time finding some mineral oil for my R12 system, never did get some today. One guy even said to use baby oil? Has anyone ever tried that? don't think I will. Instead of wasting $50 in gas, I'll phone around tomorrow from work.

Chick on Thu July 10, 2008 6:49 AM User is offlineView users profile

do not use baby oil, or drug store mineral oil, it's not the same. Can't believe you can't find mineral oil though.. Try a refrigeration supplier.. Of you are completely changing the oil due to flushing, I recommend a quality ester like BVA auto 100 which will work fine with R12 or R134a.. hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Cussboy on Thu July 10, 2008 2:15 PM User is offline

AMA (board sponsor) lists it #41-50000, at $6.50 for a quart.


https://www.ackits.com/pc/41-50000/Compressoroils/Mineral+Oil+525+Viscosity+%28Quart+Bottle%29

b_train_98 on Thu July 10, 2008 8:47 PM User is offlineView users profile

I wish I knew about that awhile ago. After getting the run around I finally found some oil. It's not the best though. It just happens to be DuraCool universal a/c oil. I have had DuraCool in the system before so that part is good. $25 for a bottle that I'll only need half of! As I understand I have to throw out what I don't use. I will charge my system this weekend and see what happens.

b_train_98 on Sun July 20, 2008 11:02 PM User is offlineView users profile

And it continues! I replaced a bunch of seals, accumulator, oil and orifice tube. I finally charged it today. One can brought it up to 25 psi from empty. I had to jump the compressor while charging it. I disconnected my jumper wires and plugged everything in normally. The compressor still doesn't kick in. I don't know if it even got cold, I was by myself and didn't want to run the compressor to long on the jumper wire. It did kick in when I jumped it, looks like it works fine. Before I left home, I checked the pressure again. 100 psi!! I have no idea what happened. What do you guys think? I'm stumped!

b_train_98 on Wed July 23, 2008 6:17 PM User is offlineView users profile

I have a full charge in it and it still won't kick in. The highest it went to was 100psi. Did I stump you guys to or everyone been busy?

b_train_98 on Wed July 23, 2008 11:43 PM User is offlineView users profile

Do I have a evaporator thermostat? That would explain why I don't have 12v at the relay. 93 Explorer Eddie B

Chick on Thu July 24, 2008 6:19 AM User is offlineView users profile

Does that have ATC or manual AC? you may have to trace the wiring all the way from the control head forward. You are gonna need a wiring diagram of the system. And make sure the blower speed control module is plugged in, under the hood in the evap box.All I can think of without my hands on it..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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