AC wiring

f117rt

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AC compressor won't engage when AC is turned on.

If I connect the compressor wire to +12v at the battery, the clutch engages ath the compressor.

I checked the wire going to the compressor and it gets +12V!

When I connect the wire the clutch does not engage!

Doesn't make sense.

Any suggestions out there?

 

72HCODE

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Getting voltage but not the Amps to hold the clutch then I suspect.

There is a micro switch on the back of the slider controls when you flip the slider to AC fresh or max the switch kicks on and you can hear the click at the compressor clutch if it is silent in the garage.

There is also a temp switch located behind the glove box insert on the AC box body. I would check the connections there and see if something is loose.

Also the main connector that is on the left side of the slider controls for the fan switch you can reach it from the drivers side foot well I would make sure it didn't get loose.

Make sure with the volt meter that if you move the slider to heat on the climate panel that you read 0 volts at the AC compressor clutch power wire, that would at least tell you the micro switch is working on and off.

Replace the AC fuse also and clean the fuse contacts to the right of the steering column. You can have problems with a half blown fuse down corrosion down there. So pull the fuse and replace and then brush the fuse box contacts to make sure then pop the new fuse back in.

 

f117rt

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Getting voltage but not the Amps to hold the clutch then I suspect.

There is a micro switch on the back of the slider controls when you flip the slider to AC fresh or max the switch kicks on and you can hear the click at the compressor clutch if it is silent in the garage.

There is also a temp switch located behind the glove box insert on the AC box body. I would check the connections there and see if something is loose.

Also the main connector that is on the left side of the slider controls for the fan switch you can reach it from the drivers side foot well I would make sure it didn't get loose.

Make sure with the volt meter that if you move the slider to heat on the climate panel that you read 0 volts at the AC compressor clutch power wire, that would at least tell you the micro switch is working on and off.

Replace the AC fuse also and clean the fuse contacts to the right of the steering column. You can have problems with a half blown fuse down corrosion down there. So pull the fuse and replace and then brush the fuse box contacts to make sure then pop the new fuse back in.
Thanks, will check that today,

With the meter on the compressor wire I did check the voltages:

Fan off = 0v

Fan ON with lever not on MAX or fresh = 0v

Lever on Max or fresh with fan On = 12V

So it seems that the switches work properly.

 

72HCODE

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ok switch works now you could check the sensor behind the glove box insert.

there is 2 connectors going to the temp sensor one green and one black from memory.

you could bypass that by connecting together and check to see if the sensor went bad which would cut power to the compressor.

that would bypass the temp freeze sensor on the compressor power line.



from beyond that you could have a broken wire in the system trace the wire from the a/c compressor to the firewall connector there should be a 3 or 4 pin rubber boot connector behind the block on the drivers side firewall.

pull that apart and inspect for problems.

that black wire for the compressor goes back to that sensor switch behind the glove box which then goes to the fan duct electrical plate.

Going back into the car in the drivers side foot well up to the fan duct motor you will see a red plate with electrical connections.

pull that all apart and clean the corrosion off

picture of area



the plate has the connector for the fan duct motor speed and also ground. you can check all those wires and clean all the connectors to weed out issues.

the fan ground is up inside the dash with a phillips head screw you can reach it from the drivers foot well if you take out the drivers seat and climb in down there.

i would take out the drivers seat to make all the electric checking easy anyway.

ford crimped all those wires so it is possible there is a bad high ohm connection at one point or a wire fractured causing the clutch to not engage due to low amps but the voltage is reaching the clutch. if you have an ohm meter with alligator clips you could trace all the points and spot a super high ohms reading as a point of failure.

cleaning the connection points will drop resistance as well.

 

f117rt

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1971 Conv; 1 of 17; 351C, 2V, Auto
ok switch works now you could check the sensor behind the glove box insert.

there is 2 connectors going to the temp sensor one green and one black from memory.

you could bypass that by connecting together and check to see if the sensor went bad which would cut power to the compressor.

that would bypass the temp freeze sensor on the compressor power line.



from beyond that you could have a broken wire in the system trace the wire from the a/c compressor to the firewall connector there should be a 3 or 4 pin rubber boot connector behind the block on the drivers side firewall.

pull that apart and inspect for problems.

that black wire for the compressor goes back to that sensor switch behind the glove box which then goes to the fan duct electrical plate.

Going back into the car in the drivers side foot well up to the fan duct motor you will see a red plate with electrical connections.

pull that all apart and clean the corrosion off

picture of area



the plate has the connector for the fan duct motor speed and also ground. you can check all those wires and clean all the connectors to weed out issues.

the fan ground is up inside the dash with a phillips head screw you can reach it from the drivers foot well if you take out the drivers seat and climb in down there.

i would take out the drivers seat to make all the electric checking easy anyway.

ford crimped all those wires so it is possible there is a bad high ohm connection at one point or a wire fractured causing the clutch to not engage due to low amps but the voltage is reaching the clutch. if you have an ohm meter with alligator clips you could trace all the points and spot a super high ohms reading as a point of failure.

cleaning the connection points will drop resistance as well.
Thanks, will check in the morning.

 
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