AC Compressor Not Engaging
08-02-2011, 12:21 AM
#1
Racer
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AC Compressor Not Engaging
I had the AC converted & recharged about a month ago. The mechanic said the pressures were good and checked for leaks and didn't find any. The AC worked well for a little while however the compressor will not engage anymore.
I replaced the resistor attached to the condenser as it was shot. That fixed the condenser fan cycling but not the lack of engagement. I hardwired 12v to the compressor and the clutch engages.
The 7.5 amp fuse is not blown. I swapped the rear relay for one of the two in the front compartment and it didn't change anything. One thing I did notice was that the slot for pin 5 that accepts the condenser relay was blackened. Does anyone have the wiring diagrams for the pressure switch and AC system. I am an EE and I feel blind without schematics! I found some comment saying that pin 5 for that relay should have 12v however I read it as 0. Pin 3 had 12v.
I found somewhere that said pin 7 should be 12v, however I read 0 volts.
Any other ideas?
I replaced the resistor attached to the condenser as it was shot. That fixed the condenser fan cycling but not the lack of engagement. I hardwired 12v to the compressor and the clutch engages.
The 7.5 amp fuse is not blown. I swapped the rear relay for one of the two in the front compartment and it didn't change anything. One thing I did notice was that the slot for pin 5 that accepts the condenser relay was blackened. Does anyone have the wiring diagrams for the pressure switch and AC system. I am an EE and I feel blind without schematics! I found some comment saying that pin 5 for that relay should have 12v however I read it as 0. Pin 3 had 12v.
I found somewhere that said pin 7 should be 12v, however I read 0 volts.
Any other ideas?
Last edited by mrmandmman; 08-02-2011 at 12:41 AM.
08-02-2011, 05:59 AM
#2
Rennlist Member
Pin 3 is the fused 12v input power to the NO contact of the relay
Pin 5 is the output of that relay to the compressor
Pin 2 is from the CCU then to the high/low pressure switch then to one side of the coil
Pin7 is essentially ground of the coil
Pin 5 is the output of that relay to the compressor
Pin 2 is from the CCU then to the high/low pressure switch then to one side of the coil
Pin7 is essentially ground of the coil
08-02-2011, 04:59 PM
#3
Three Wheelin'
Hate to state the obvioius - but double check your pressures. I had the oddest leak in my S2. It would hold a vaccum at the shop for HOURS - and work great for 1-2 days - then loose all the R-12A. Top it up - compressor engages - works great - for 2 days... etc.
For yours to have failed again a month later? Entirely feasible. Check that first.
RK
For yours to have failed again a month later? Entirely feasible. Check that first.
RK
08-03-2011, 06:10 PM
#5
There's a small shim in the clutch. I just recently had my AC serviced, and the tech noticed that the clutch gap seemed too large, and was causing the clutch to not engage at times.. He changed out the shim to .18", I believe, from .41", and it started working reliably.
My 2 cents.
Clay
My 2 cents.
Clay
08-03-2011, 07:40 PM
#6
Three Wheelin'
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Hate to state the obvioius - but double check your pressures. I had the oddest leak in my S2. It would hold a vaccum at the shop for HOURS - and work great for 1-2 days - then loose all the R-12A. Top it up - compressor engages - works great - for 2 days... etc.
For yours to have failed again a month later? Entirely feasible. Check that first.
RK
For yours to have failed again a month later? Entirely feasible. Check that first.
RK
There's a low pressure limit switch on the system that prevents the compressor operating when the pressure is too low.
Sorry to suggest that you may have sprung a leak, which = $$$.
