Hi, new here. Searching out my ac problem led me here, there's a ton of info here wow.

Ok searched the other threads and after troubleshooting I thought it was a bad ecu, until I changed it.
98 dx ac is charged, push ac button condenser fan comes, on engine speeds up slightly for a bit, compressor does not run. If I jump the relay I can make ac compressor run, blows cold.
Jumping pressure switch doesn't do anything.
At ecu pin a17 has voltage to ground when car running, does not switch to a ground when ac button pushed.
Black/red wire at pin a17 has full continuity to ground pin at clutch relay underhood. Clutch relay has power. All fuses good.
All things seem to point to a bad ecu.
Only concern I have is at pressure switch if I test for voltage at blue/red wire I get nothing.
Did I miss something or did I get another bum ecu?
Your help is very much appreciated!

 

Test the Blu/Red wire for an open between the pressure switch plug and ECU pin C5.

 

Thanks for the quick reply. Unfortunately the car just left, I'm helping my sister in law it's her car. I'll be back at it tomorrow.


Hypothetically say the line is open between blue/red and The c5 ( I'll assume that's on the c plug?) where do I go from there? Just tying to be a couple steps ahead since the car isn't here all the time.

 

Ok fixed it
Ron thanks for the help!
Tested for continuity between blue/red at pressure switch and c5 at ecu, open line. Turned the key on tested for 5 volts at c5 back probing when plugged into the ecu, had 4.5 volts. Ok broken wire.
I have a telephone probe and tone tool, put a tone on the wire at ecu and followed with the probe, lost the tone behind the grill. Pulled the wire out and it had 3 little holes from I'm guessing bad manufacture and the water had got in and corroded it. Cut it out, 2 inches of new wire, fixed.
Thank you so much for your help Ron and thanks for this board!

 

Great job. I love the creative use of the phone probe/tone tool.