99 malibu...temp gauge & AC


gpmodelj70
08-14-2016, 07:42 PM
Hello,
I have an issue which has stumped me...sitting at idle, the AC and temperature gauge works properly...if I pull out onto the road, then at ~10 mph and up the temp gauge goes to zero and the ac clutch disengages...any ideas?..this happens together every time.

brcidd
08-14-2016, 09:08 PM
Is yours a manual a/c system (no digital readout for temp control) if so read on:

Does the green a/c indicator light go off as well-- if so wiggle the fan speed switch- it acts as the "Master" on-off switch for a/c- and the contacts get hardened grease on them that disables the a/c command-- seen a bunch of them. Fix is to remove blower switch and polish the contact surface area with a pencil eraser....

gpmodelj70
08-14-2016, 09:13 PM
the indicator light does not go off...is it possible that the ECM is losing its signal for engine temperature and shutting off the AC on purpose?

Kristi'sChevy111
10-02-2016, 12:23 PM
Our 08 Mailbu is doing sort of the same thing. The temp gauge does not move at all & the a/c doesn't work at all. We disconnected the battery and everything works for a couple days then goes inop again. We changed out the Engine Coolant Temperature Sensor but that didn't help. We don't want to keep throwing parts at the car so if you find a fix for it please let me know.

Stealthee
10-02-2016, 04:24 PM
If the ECU does not see voltage from the coolant temperature sensor it will disengage the AC clutch. It is a failsafe. It basically sees no voltage as an overheat. When it overheats it will disengage the AC clutch as well.

Blue Bowtie
10-03-2016, 08:26 AM
In summary, the CTS itself has been replaced but the problem remains. This may be due to open circuits in the wire harness, including connectors, splices within the harness, and wires themselves. The fact that it is intermittent will make it more difficult to locate. A factory service manual with schematics will be very useful in determining all the connectors and areas involved in the CTS circuit.

gpmodelj70
05-09-2017, 08:13 AM
I still have not resolved this issue...I unplugged the ECT connector and used a 400 ohm resistor...gauge still drops to "cold" whenever the car is rolling...to be sure someone has resolved this issue on their car!?

gpmodelj70
05-09-2017, 08:14 AM
Does anyone have a factory service manual with wiring schematics that can send me a scan?

03GMCSonoma
07-17-2017, 11:10 AM
I have an 07 Malibu with 2.2l engine doing the same. Intermittant temp gauge reading cold, and A/c not working when this happens. Looking for answers. No check engine light coming on either.

gpmodelj70
07-17-2017, 01:37 PM
Is yours a manual a/c system (no digital readout for temp control) if so read on:

Does the green a/c indicator light go off as well-- if so wiggle the fan speed switch- it acts as the "Master" on-off switch for a/c- and the contacts get hardened grease on them that disables the a/c command-- seen a bunch of them. Fix is to remove blower switch and polish the contact surface area with a pencil eraser....

Did that...no change...still same issue...swapped out the dash control with a known good one...no help

gpmodelj70
07-17-2017, 01:41 PM
Connected scanner to monitor engine coolant temperature while car is in motion...computer disconnects from the scanner at the same time the temperature gauge drops to zero and AC clutch disengages

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