2000 Ford Mustang A/C Just quit working

Tiny
STANGJOE
  • MEMBER
  • 2000 FORD MUSTANG
  • 6 CYL
  • 2WD
  • MANUAL
  • 104,000 MILES
I drove my car home and parked it for 30 mins, the air had been working fine. I got in and started it up, and the air wouldnt blow cold. I checked and the A/C clutch wasnt enaging. I jumped the low pressure switch, and the only thing it did was raise the engine RPM. Removed the jumper and the RPM lowered. Checked the system and its at the proper pressure. So I used a meter and checked the connector going to the compressor. I am getting 13 volts to the connector when the a/c is turned on. However, when I plug the connector in, the clutch does not engage. So I jumped the compressor to the battery. The clutch engages and the car blows cold air. So, I have 13 volts at the connector, no clutch engagement and if I provide power from the battery then the clutch engages. If I run leads from the connector to the compressor, it wont engage. So now I am lost. Oh, when I run the leads from the connector to the compressor, it seems to be pulling.5 amps, when I run the leads from the compressor to the battery, it seems to be pulling 4 amps.

I appreciate any help you guys can offer!

Thanks.
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Wednesday, May 6th, 2009 AT 7:53 PM

11 Replies

Tiny
RACEFAN966
  • EXPERT
Ok I need you to do some testing. You will need a digital multi meter for these tests. First you will unplug the A/C cycling switch and then check the ohms of resistence between the violet wire and ground. Then with the a/c selector in the a/c position check the high pressure switch unplug the harness there and check the ohms between the dark blue wire with yellow stripe and ground too. Lets start there and see what we find. Thanks
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Thursday, May 7th, 2009 AT 10:28 AM
Tiny
STANGJOE
  • MEMBER
Sorry for the delay in replying. I am not great at auto electrical, so here's what I found.

I disconnected the cycle switch and checked it and got a reading of 1 with the a/c off. When I turned the a/c switch to on, I got a reading of 374.

Not sure where the other switch is, but I am guessing its the connector to the compressor, as it had a ground wire and an dark blue with yellow stripe wire. From there it was 3 ohms with the a/c turned on. Hope that is what you needed, please let me know. I appreciate your help, its getting so hot out here!

Thanks
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Thursday, May 14th, 2009 AT 2:25 PM
Tiny
RACEFAN966
  • EXPERT
OK so far so good. Now there should be a violet wire at the A/C compressor switch. I need you to unplug that and check the resistance between the violet wire and ground should be 10k ohms or more if it is less then that then you need to check that wire for any breaks or shorts. If it is more then 10k ohm then you need to do the next step.
Plug the switch back in and back probe the violet wire with a paper clip and connect your meter between that and ground and then you will need to set it where you can see it from inside the car and then rotate the selector switch and put it in all possitions. If any possition is less then 10k ohms during this then the selector switch is no good. If all is good here then get back back to me and we will go to the next step. You are welcome I am a Ford and Mustang guy myselft. I also have a 98 Mustang V-6 with many mods and for summer and a 95 F-150 for winter. Glad to try to help. Let me know what you find.
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Friday, May 15th, 2009 AT 8:32 AM
Tiny
STANGJOE
  • MEMBER
Ok, I hope I tested at the right point. I disconnected the cycle switch plug (the one you jump to see if the low side switch is bad). I put the meter on 20k ohms and put the red lead to the purple wire and the black lead directly to the negative side of the battery. For the most part the meter just read 1 or changed to -1 when the selector inside was turned from off to normal a/c or to max a/c. If I moved the black lead some, sometimes it would give more numbers, but nothing consistent.

The part of this that is really killing me is that if I provide positive power from the batter and ground from the clip into the compressor it kicks right on. However, I get voltage at the clip of 14 volts but it wont turn the compressor on.

This problem really has me hitting my head! Again, I appreciate your help and will gladly donate more when we get this fixed!

Thanks!
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Saturday, May 16th, 2009 AT 8:09 AM
Tiny
RACEFAN966
  • EXPERT
OK no worries we will get this it just takes a bit longer to do this over the net as apposed to having the car infront of me. Now what I would like you to do is first check the a few fuses. Fuse number 2, 23, 24, they should be a 20 amp, 15amp and 30 amp in that order, these are in the fuse box inside the car. I also need you to check the black wire with the yellow stipe at the a/c clutch. This is the power wire to the clutch coils and with the car on and the a/c on max do you get power there? If not then you need to find the A/C relay in the relay box behind the engine coolant reservior and check that the red wire is getting power to the relay. If that is good then check the dark green wire with the orange stripe at the relay to see if it has power. If this don't have power then I need you to check the fuse in the junction box that is infront of the drivers strut tower. It is the 20 amp fuse for the a/c relay, make sure it is good. I know this is a lot to check and if you have any problems please just ask. Let me know what you find here.
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Saturday, May 16th, 2009 AT 9:14 AM
Tiny
STANGJOE
  • MEMBER
Ok, I checked the fuses and they are good. I also checked the wire going to the a/c clutch and am getting 14 volts there, so do I need to check the other wires you listed since it has voltage? I completely understand the time it takes over the internet and truly appreciate the help.
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Saturday, May 16th, 2009 AT 9:45 AM
Tiny
RACEFAN966
  • EXPERT
Ok no if you would unplug the ac clutch and check resistance across the terms of the clutch. Get back to me with what you find. So far sounds like a bad clutch coil. Thanks
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Monday, May 18th, 2009 AT 9:51 AM
Tiny
STANGJOE
  • MEMBER
Well its raining right now, so I'll have to check that tomorrow.

If it was a clutch coil, why would it turn on when I run power directly from the battery and ground from the connector? Just asking, as I am not good with electrical, but thought it made sense.

As for checking resistance across, put one lead to each end of the connector and check the ohms, right?
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Monday, May 18th, 2009 AT 8:15 PM
Tiny
RACEFAN966
  • EXPERT
Sorry your right some times I forget to read back to make sure where we are at. With that I need you to find the A/C clutch relay and the EDF relay next to it. These are in the relay box behind the coolant resersior. I am thinking that one of these are getting overheated and shutting down there for needing replacement. Everything else you tested checks out good so far so that is the only thing that makes sense. Once you find them then I need you to check to see if the pink wire with the yellow stripe to the ac relay get power when you turn it to ac. Then check to see if the EDF control relay get power from the dk blue wire. Let me know what you find.
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Tuesday, May 19th, 2009 AT 9:31 AM
Tiny
STANGJOE
  • MEMBER
I dont have a box behind my coolant res, as it is in the front center of the engine compartment, right behind the fan. The only box I see is behind the batters and the washer fluid res. If thats the box, then:

Which two fuses? Are you referring to the A/C Press fuse (20amp - Constant Control Relay Module)? And what is the EDF relay?

Sorry for the confusion.
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Tuesday, May 19th, 2009 AT 9:44 AM
Tiny
RACEFAN966
  • EXPERT
Yes that is the fuse that I am refuring to. It is the a/c press fuse 20 amp. Let me know if that is blown and the edf relay control sends power to the a/c relay and according to mitchell on demand it is located on a bracket behind the coolant reservior. They are calling this unit a constant control relay module and hold the edf and hedf relay and edf relay control and a/c relay thats it. Let me know if you find it and if not then if you would get me the actual production date of you Stang and I will look again. Thanks.
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Tuesday, May 19th, 2009 AT 9:07 PM

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