1999 G/T 4.6 A/C clutch not engaging.

[David B.]

I started at the fuse. Found a good 30-amp fuse. Replaced it with a proper 15-amp fuse. Next, hooked the gauges to low and high sides. Good static pressure. Checked for power through the low- and high-pressure cutouts. Power in and out of both switches. (I am guessing the other 2 wires on the high side are for cooling fan high speed if high pressure cutout makes!). Next to the CCRM. It is not burnt or any signs of overheating. Bench tested the clutch relay, coil checks out. When contacts are MADE I have continuity through contacts. To eliminate the CCRM I purchased a NEW one and replaced it! When the A/C mode switch is set to any A/C position the idle picks up. I pulled the clutch coil plug and wired it to 12 volts and the clutch pulls in. Coil checks out OK. If anyone can tell me what I'm missing, it would be appreciated! To me it looks like I'm not getting a A/C request from the ECM!

 

[89ripper]

Hmmmm do you have a good charge of refrigerant? Sounds like low pressure, just a guess

Edit: nevermind reread your post. Sorry its late at work haha

 

[David B.]

Thanks 89ripper. If this was A pre-ECM vehicle the clutch would pull in! UPDATE: I dropped a 30 amp. relay in on the wheel well. I fished a wire over to the battery, fused 15 amp, grounded the coil to the relay mounting screw. The contact side- Tapped of the high pressure switch 12v. out side. Tapped the 12v pos. wire to the clutch coil. I didn't cut any wires I tapped off the existing wiring because the idle jumps up when selector switch is switched to any A/C position. The ECM is getting a A/C request from the mode selector switch but not sending the request to the CCRM. (I replaced with a NEW one not a reman.) Now the clutch pulls in and A/C works fine. Cools good! The test will be on the 90 degree plus days to come. So far the temp. has not gone over 190 degrees. I have a new radiator and fan so as long as the cooling fan jumps to high speed when required, I don't see a down side to this I still have the cycling switch's for compressor protection. I soldered and heat shrink on all the connections and ran wires in wire loom. This tells me the ECM is not sending A/c request to the CCRM. I have a BDX mounted on the dash so I can keep track of coolant temp. Again, I don't see a down side to this! If anyone does see a problem with what I've done please tell me!