A/C Compressor Not engaging??

[zr1esq]

1991 ZR1 40K - blinking head unit states low freon. Bought this r12 substitute stuff from amazon - supposed to be decent - however no compressor action?? Fuse checks good - jumped at all pressure switches - nothing. Removed negative battery cable - nothing. Physically I can move clutch on compressor but its not engaging. Am I missing something? Bad compressor? Any other test I should be doing. I didn't find anything in the search and the FSM is very vague. Help!

[Dynomite]

Originally Posted by zr1esq

1991 ZR1 40K - blinking head unit states low freon. Bought this r12 substitute stuff from amazon - supposed to be decent - however no compressor action?? Fuse checks good - jumped at all pressure switches - nothing. Removed negative battery cable - nothing. Physically I can move clutch on compressor but its not engaging. Am I missing something? Bad compressor? Any other test I should be doing. I didn't find anything in the search and the FSM is very vague. Help!

If like other AC compressor clutches there is a shim washer or shim washers keeping the clutch hub spaced correctly with the clutch surface (serpentine belt pulley). If there is too large a space between the outer hub and the clutch surface the magnetic field cannot engage the clutch.

I think if you apply 12 volts to the AC Compressor the hub should pop in...if not, the gap is too large and shims should be removed. It appears not easy to hot wire the AC Clutch on the LT5 to check (one should check if there is 12 volts at the AC Compressor with AC ON). Also.......you can hot wire the pressure switch on the Dryer Side of the AC checking for 12 volts there as well. On other vehicles it is a 15 second job to hot wire the AC Clutch and a 5 minute job to remove a shim on the center bolt. You want to Hot Wire the AC Compressor right at the compressor just in case there is an issue with providing 12 volts to the AC Compressor with AC On anywhere else in the electrical wiring to the AC Compressor.

[RICHARD TILL]

The high pressure switch is normally closed until excessive pressure and the low side switch is normally open until enough pressure is detected to engage clutch. How do they now check? Got voltage at either side of the low pressure switch?

[zr1esq]

When I jump the high pressure switch I get nothing - any other car would always make the compressor engage. I will check for voltage tomorrow in the switches

[zr1esq]

Ok with ignition on and not running. I pulled the plug from the switch under the overflow tank and measured .578 volts. Then next to the motor, there are two more switches. again I measured .578 on one switch - the other switch I unplugged and the secondary cooling fan turned on. When I pulled both switches no voltage was measured at either switch. What do you think?

[randy ransome]

Have you made sure the codes are erased.
My compressor wouldn't do anything either until the low freon code was deleted.