a/c help big problems

[seeinzs]

got a 94 taurus and a/c stopped working all of a sudden. i have no power to or from the ccrm. i do have power going to the low and high pressure switches but just to the switches. i also do have power from the switch in the car. the only way i can make the compressor come on is sending straight power to it.

[brcidd]

The ccrm's are known to go bad for the a/c circuit- last 2 I saw, I fashioned an external relay, in parallel to the ccrm to complete the circuit- works great- only cost $7 as opposed to $100 plus- a wiring diagram helps- shows you what colors to use to wire your relay..

[seeinzs]

i got another ccrm from a junk yard and still no power to and from it. r the low n high pressure switches suppost to have power to them but not from? it has 45 psi right now in the system also. do u have any idea what i can check that is suppost to send power to the ccrm

[seeinzs]

just went outside n changed the ccrm again. i bought like 3 from a junk yard for $10 bucks each. i didn't mention either the low pressure switch is new. i just checked for power still no power at the ccrm but i have power to and from the low pressure switch now. but still only power to the high pressure switch.

[brcidd]

So 45 psi is probably not enough to engage the low side switch-- should be at about 85 psi at ambient of 70+ degf-- go ahead and jumper the switch connectors- see what happens

[seeinzs]

jump the low pressure switch? but would that have anything to do with the ccrm not getting power? i'll go try it

[seeinzs]

nothing happens when you jump the low pressure switch..... i have power coming into the 'Lp' switch from a purple wire then coming out from a red/yellow wire which goes to the high pressure switch. there r 3 other wires on the high switch tan/green, black, and pink/blue. they have no power, i dont know if they r suppost to or not. but still no power to the ccrm wires numbered 22, 23, and 24. which i found on an a/c website saying they retrieve and send the power to the clutch.

[seeinzs]

still cant figure this thing out.....no power to ccrm, but i noticed in the wiring going to the ccrm there are 2 ground wires that have a plug that grounds out to the body then to the battery. these wires get extremly hot.

[shorod]

Originally Posted by seeinzs

nothing happens when you jump the low pressure switch..... i have power coming into the 'Lp' switch from a purple wire then coming out from a red/yellow wire which goes to the high pressure switch. there r 3 other wires on the high switch tan/green, black, and pink/blue. they have no power, i dont know if they r suppost to or not. but still no power to the ccrm wires numbered 22, 23, and 24. which i found on an a/c website saying they retrieve and send the power to the clutch.

On the high pressure switch the black wire goes to ground. The tan/light green is the High Speed Fan Control (HFC) input to the Powertrain Control Module (PCM). The Pink/Light Blue wire is the A/C clutch control line and should be active when the high pressure side is between 150 and 250 psi. I can't tell however if it is active high or active low. It goes to both the PCM and the CCRM which makes me wonder how it is supposed to operate. I suspect that it's active high since that's what the low pressure switch is.

-Rod

[tripletdaddy]

Hmm......., there's such good information at the top of this forum on this.....:

Your high pressure/fan control switch (four wires to it and behind the compressor) is not allowing power to the ccrm, which you've already figured out, most likely due to it failing, maybe the internal switch is stuck open. Now, Rod got the wires to it right, but the operating pressures ... well... just use mine if you need them, they are from a reputable source. The switch should allow power through it to the ccrm at all times unless the pressure at it is above 420 psi. When that does happen, it won't turn on the power until the pressure goes below 250 psi. It also will turn on the high speed fan when the pressure goes above 325 psi and will return it to low speed when the pressure drops below 275 psi. FYI, the clutch cycling switch will only turn on when the pressure is above 45 psi, and will turn off only when the pressure drops below 25 psi. Yes it seems a bit backwards but it works that way. Your defective switch sounds like it may even be shorting power through the ccrm, since you said the ground wires are quite warm.

So, if the switch is good, you should have power in at the R/Y wire and out at the Pk/Lb wire (or continuity with wiring off) . The T/Lt G wire to the Bk wire should be open wires disconnected. These should test this way with everything off. This switch is expensive, so your cheap parts yard may be worth the risk but electric test it first.

Good luck, let us hear how it goes.

[seeinzs]

ok the high pressure is around 200 to 235. but let me ask you this if the high pressure switch is bad it wouldnt send power to the ccrm wire #21 so then would that make the pcm not send power to wire #22..i just have power coming out of the low to the high then stops completely. i will try to test the high switch. well i guess its bad though because it should continue out of the red/yellow through the pink/light blue right? the switch is like 30 bucks at oreillys. should i just go buy it n try that?

[seeinzs]

can you replace the high pressure switch without evacuating the system or can you replace it just like the low pressure switch?

[tripletdaddy]

Let me start by making a chart of the pin descriptions for the ccrm.

Pin Wire Color Description
16 GY/W AC clutch power feed (-)
21 PK/LB AC relay control feed from hi press switch & PCM
22 PK/Y Wide open throttle ac cutout, signal from PCM to stop power to clutch at hi rpm
23 BK/Y AC clutch (+) power feed
24 R Battery (+), should be there always but
not part of AC circuit of concern here

If hi press sw is bad, then there will be no power from it to pin 21 of the ccrm, or, if there is power to the hpc sw but none out to the ccrm, then it's bad. Though no power through the sw is a test of power continuity, you could use a resistance continuity test to prove the same. Based on what you've said, it's bad. Pin 22 is not involved here as it is only used for when accelerating hard to direct more power to the trans.

From what I can glean from the Ford SM, they do not say you need to discharge it to remove the sw, so I assume it's the same as the low side sw you changed with the check valve. Now why couldn't they have been more detailed on the hpc sw removal as they were with the low press sw escapes me. They say to use new lubricated seals with AC oil and also on the new sw and the fitting, pretty much oil everywhere, your head, your kid, your dog, your neighbor. :

[seeinzs]

i jumped the red/yellow wire to the pink/blue wire at the high sw and the compressor kicked on and is cooling great. so i assume the switch is just bad. i'm gonna replace it today and i'll let ya know what happens, thanks

[seeinzs]

i put the original ccrm back in just to check then replaced the high pressure switch. $29 oreillys. and still nothing so i put the ccrm back in that i got from the junk yard. $10 at a u-pull-it place. and now it works great! i guess the h/p switch shorted out n burned the original ccrm up. thanks a lot u guys you helped me out a bunch!