View Full Version : A/C button flashing

06-13-2013, 01:13 AM
I have searched hard and have looked through the bgb for hours. I have a 93 GTS with auto a/c. I push the button to turn the a/c on and the compressor kicks on and the engine begins to idle up and then the compressor kicks off and the light begins to blink. It will repeat this process as many times as you reset the button. I do not have a set of gauges but the can I used to charge the system showed the low side in the blue. I also jumpered the pressure switch connector and got the same results. If I bypass the clutch replay the compressor will run and actually put out cool air. I have read that it could be the rpm sensor but it checked out at 100 ohm. I checked the a/c amplifier wiring per the bgb and had several issues. Pin 1 had 9v with the a/c switch on. Pin 6 had no voltage with the a/ switch off. Pin 8 had 12v with the a/c switch on. Pin 13 had 12v with the a/c switch turned off. Pin 18 had 12v with the engine shut off. I read the the a/c amplifier will kick the compressor off if the rpm are to high. According to the bgb the act signal from the ecu to the a/c amplifier is supposed to be 4.5 - 5.5 volts, I was getting 12v at pin 11. I recently changed out my tach and got it from another 5th gen but don't believe it was a gts. The tach works but I'm wondering if it controls the signal to the a/c amplifier in some way.

I know this is a ton of info to sift through but would really appreciate some help. Thanks for your time.

06-13-2013, 02:00 AM
have you tryed putting in ur old tach and seeing what happens? or unplugging the new altogether? also check ur relays and fuses

06-13-2013, 02:24 AM
Thanks for the quick reply. I have check the fuses and relays and all are fine.

This is going to sound stupid but how would I unplug my tach? I replaced the one in my combo meter. Is there one plug on the back of the combo meter just for the tach? Sorry it's been awhile since I had it apart.

06-13-2013, 02:31 AM
srry i ment unplug the whole cluster and then see what happens. im also not sure what u mean by combo meter

06-13-2013, 02:37 AM
I mean the cluster, The bgb calls it the combo meter. Thanks again for the reply, I'll try it in the morning and give an update.

06-13-2013, 02:50 AM
Combo meter IS the cluster since it all runs off of the same circuit board assembly. You can replace individual items in it though.

06-14-2013, 07:45 PM
I pulled pin 18 from the ac amplifier connector. That is the wire that runs from the tach. No more blinking light and the compressor is running and blowing cold air. It blows cooler at idle than running down the freeway. Does anyone have any ideas? My guess is that although the rpm sensor ohms checks out, it is not working properly and not reading consistent with the tach signal. Basically there is a matching no signal to the amplifier now and it is running great at idle. Now I'm wondering since the signal doesn't change while driving that the ac amplifier can't optimize the performance while driving? I hope there is a ac guru around to give some guidance.