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Discussion Starter · #1 ·
Hi all, I have a 99 escort zx2 that I would like to wire in an external set of relays to engage the a/c compressor and turn the cooling fan on high. Here's what I want to do, but I have a couple of questions. But first things first... I found a bad WAC relay for the a/c compressor clutch in the CCRM, and tried (with little finesse) to replace the relay... Oops, I made the circuit board junk for soldering in a new WAC relay by losing patients and yanking the old relay out (it came out all righty :devil:).

I want to hook up a toggle switch to a relay that will close a switch to ground pin 17 (Which should close the switch for the cooling fan on high speed). Also, my toggle switch will close another relay that will switch hot to pin 23, which should engage the a/c clutch. But instead of just switching the a/c clutch on, I want to send the circuit through the low and high pressure switches in the a/c system.

Question #1. If I ground pin 17 (Which is what the PCM does to turn the cooling fan on high), is it going to screw up the PCM? If so, should I install a diode so it doesn't ground where ever pin 17 goes to in the PCM?

Question #2. Does the high pressure switch actually operate as a switch? I recall reading somewhere that the high pressure 'switch' is actually a rheostat that signals the PCM to tell it how high the pressure actually is (instead of just opening a switch when the pressure gets too high on the high pressure side). It seems like both low and high pressure switches have more than 2 wires, so....

Quesiton #3. Which wires should I use on the low and high pressure switches to wire the hot wire to my compressor clutch?

That way I get the a/c to turn on, along with the cooling fan on high when I flip the switch that I will install. But, if the pressure gets too low, or too high in the a/c system, the appropriate switches built in to the a/c system will disengage the a/c compressor.

I'm not concerned with the WOT relay. I don't drive it like a race car, and I don't ever think I floor the accelerator anyway.

Thank you so much for any help you can offer.
Jason
 

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Just because you can do something doesn't mean you should.

While in theory your A/C and fan might work, you have created layers of problems. If you "trick" the A/C into working, the PCM will not calculate the idle speed correctly for the load. By running the fan speed on high, you will put additional wear on the fan motor, and alternator. Unless your pressure switches are part of the plan, you run risks of evaporator freeze up, and lose low refrigerant protection, as well as overpressure protection. By the time you run wires inside and out, mount switches, hang relays, splice wires, and install fuses... You could have been done if you installed a new CCRM, with out risking A/C, & PCM.

So I say no. Don't do it.
I know they are expensive brand new. So find a used one. Or find a rebuilt.
 

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So I say no. Don't do it.
I know they are expensive brand new. So find a used one. Or find a rebuilt.
Good advice :thumbsup:
 

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Discussion Starter · #5 ·
Makes sense.... Sometimes lack of patients gets the best of me. By the way, I planned to include the pressure switches. Have you seen some of the other bypass plans? Just running a hot wire from the low pressure switch to energize the compressor clutch? (eek!) No cooling fan..... No a/c off..... I'm a toggle switch kind of guy. heh.... and the local salvage yards don't have my model of CCRM. I can check on line, but then again, with this being such a common problem I would likely just get another bad ccrm. And they're over $200 new from Ford. (No thanks!) I figured the idle speed adjustment was negligible. The PCM will want to keep the idle at around 800-900 rpm no matter what the load is. I thought about a separate switch for the cooling fan, but I'm not the only one driving it. Thanks for the advice, though. It sounds wiser than extra wires and relays. :)
 

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I'm sorry Jay, I didn't take the time to read your whole post, but can't you rebuild the CCRM? I imagine that if it is taken apart that is has 2 or 3 relays in it, Can't you solder a working relay into it?

One thing my dad taught me is that if something is broken to the point that you are going to replace it, it doesn't hurt to take it apart to see if you can fix it because even if you break it more, it doesn't matter.
 

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Discussion Starter · #7 ·
Yeah... I even bought the replacement relay to solder in, too. The problem is that i think I damaged the circuit board getting the old relay out. :blush2: The green stuff is all scratched off where I think it would make connections where it’s not supposed to if I soldered a little sloppy. I thought about using some sort of nail polish to cover the tracks back up, but I think I just pretty much ruined the board around the a/c relay. . I'm worried that if I solder back on the board that I'll end up shorting something out and making matters worse. I have seriously considered just getting a CCRM from a salvage yard and soldering in the relay I bought if need be.

The car is running fine with the damaged board without the a/c relay on it. So I left well enough alone and just took time to ponder the possibilities.

I have pretty much everything I need to wire in the relays like I thought would work (above). I just don't know if I'm going to screw up the pcm by doing it. I understand the added wear and tear on the cooling fan and alternator. It's just hotter than you-know-what outside and I want the a/c to work. Way to go Ford for using a relay module.... how cost-effective. :eek:ut:
 

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Discussion Starter · #8 ·
Now that I've heard of a product called de-solder, I think removal of the old relay will be soooo much easier. :thumbsup:
 
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