So, I picked up a 96 accord for my daughter. clean car good price and as a mechanic I always liked honda as they are usually pretty staight forward to work on. the a/c did not work when we bought it. As temps are now staying in the high 90's here in central cal i figured it was time to get some a/c. Whipped out the gauge set and checked the charge the pressures were good yet the clutch was not engaging. upon inspection i found some tape around compressor lead between clutch and connector. removed tape and found a solder joint. This makes me believe either clutch or comp. have been replaced(wire sizes are different on each side of joint). So next i jumped from batt to comp and ac worked well and pressures looked good. checked power at relay, was good, so i switched with fan relay. fan worked, A/C didn't. so i jumpered the pressure switch. nothing. next i went inside the vehicle and pulled the glove box and jumpered the thermostat. no change. So i used my meter and found as follows: red and white input to ecu has 12v present. when switch is engaged on dash input switches to ground(continiuty to ground shows .034 ohms resistance. when a/c is turned on idle speed goes up and a/c fan turns on. At this point i am reading 4.93 volts at both comp output to relay and at the relay plug, with no continuity to ground, so the relay won't engage. Ive checked continuity of the blue/red output wire and it has perfect continuity from one end to the other so im pretty sure not wiring. I just really would like to be sure of an ecu failure before buying one. my diag experience with ecu's usually leads to an alternate problem. but in this case i cannot see what else it could be. Also checked the diode and it tests good. Any help or input would be much appreciated as temps are climbing.

 

I would unplug the pressure switch. Start the car, and have the a/c and blower turned on. Test for 12V to the red/wht wire. Also test for continuity to ground on the blu/yel wire at the pressure switch.

When you jumped the thermostat, what wires did you jump?

On the compressor relay, there are four wire. The blk/yel and wht wires should both have 12V to ground. The red/blu wire should have continuity to ground. And the red wire should have continuity to the compressor plug (one wire connector). Hope this makes sense, and let us know what you find.

 

When I jumpered thermostat it was blu/yel to blu/red. tested everything as requested and the only thing i can see wrong is im only measuring 4.55 v at the red/white wire on pressure switch. going to re check wiring diagram for possible reason. thanks for the help so far. hope to hear more ideas on my half voltage.

 

Unplug the B connector from the PCM and recheck the voltage at the red/wht wire on the pressure switch.

 

unplugged connector and have no voltage

 

i guess there was no resolution??I have the same issue.:-(

 

Welcome to the HAF site. The thread starter never continued the posting so the conversation ended. It sounds like you have A/C issues. Please post your information and we will see what we can do to help. Thanks.

 

Is there a way to jump the AC thermostat to see if the clutch will engage I tested the fan controller and there 3p thermostat connector with the pressure switch connector plugged in out jumpered and not jumpered and it reads that my pressure switch is working and I have adequate pressure in my system. But when I jumper the blue/red from the thermostat coneector to ground with engine on the clutch still does not engage .