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Discussion Starter · #1 ·
The air conditioning does not operate on my 89 Bentley. I have performed most of the test procedures as set out in the Work Shop Manuel (TSD 4700) using a multi-meter and I have not uncovered anything that indicates a problem. In doing the test for the fans control circuit I can faintly hear the relays energize, however the fans do not operate. The manual does not indicate whether or not the fans should operate when 12 volts is applied or that the relays should only energize during the test. Flying Spares has a test box for rent but it appears that all of the test procedures can be made using a multi meter. Do the mirco-processor boards become defective over time due to age and temperature conditions? Thanks for any insight you may be able to provide. Tom Greasel
 

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There are many components to an A/C system.

First..Can you verify the A/C compressor clutch clicks on and locks?
Does the system come on but not cold?
A lack of refrigerant will shutoff of the compressor
 

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I have come across the occasional board failure but not that often in my experience. Have you pulled the plug off the 44° sensor? That is a common fault that prevents operation. Also check that the ground wire under the carpet near the ACU has good contact.
 

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Discussion Starter · #4 ·
There are many components to an A/C system.

First..Can you verify the A/C compressor clutch clicks on and locks?
Does the system come on but not cold?
A lack of refrigerant will shutoff of the compressor
The compressor does not engage at all.
I have come across the occasional board failure but not that often in my experience. Have you pulled the plug off the 44° sensor? That is a common fault that prevents operation. Also check that the ground wire under the carpet near the ACU has good contact.
I do not know where the 44 degree sensor is located. The ground wire is making good contact.
 

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Thermostat housing, plug with two wires. The one with one wire is for temperature gauge so not that one. Just pull off the plugs with two wires to test. This topic has been covered many times in the past and a search should show diagrams which will pinpoint the exact sensor. It's actually just an on/off switch, normally closed, that opens at 44°C allowing operation of the ACU.
 

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This topic has been covered many times in the past and a search should show diagrams which will pinpoint the exact sensor.
Sorry for the stupid question, which one is the 44 ° sensor on this diagram ?
(1988 US specs Corniche II s/n 24509)

 

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2 wire connector on the side..not the top.
 

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I tried shorting the two wires connected to # UE 43063 sensor with no joy : compressor not turning.
(UE 44169 obviously only triggers the coolant fans)
I pulled a 12V wire connected directly to the compressor clutch : A/C blows COLD.
Any suggestion ?
 

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Do you have a 3 terminal fuse in the harness next to the comp/alt area. Do a check.
 

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You don't short the wires together to bypass the 44° switch/sensor you disconnect them. When coolant is cold the 44° switch is closed which powers a relay that prevents operation of the AC system. Once the coolant temp reaches 44° it opens and shuts off that relay and allows the system to function.
 

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Thank you for replying.
Do you have a 3 terminal fuse in the harness next to the comp/alt area. Do a check.
I’ll have a look.

You don't short the wires together to bypass the 44° switch/sensor you disconnect them. When coolant is cold the 44° switch is closed which powers a relay that prevents operation of the AC system. Once the coolant temp reaches 44° it opens and shuts off that relay and allows the system to function.
Wires going to UE 43063 shorted or not, compressor clutch won’t engage.
No joy in Defrost, either.

So far, there is no juice coming to the A/C clutch.

Anyone with a usable wiring diagram, out there ?
 

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Apparentely he has a Sanden compressor and no 3 terminal fuse ( I suggested in case he found it to replace by thermal resetting fuse)
 

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Thanks Jean, In case he had an A6 comp. But not with a Sanden.
 

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Issue is not with the clutch/compressor : A/C works fine with 12V connected straight to the clutch wire.
Compressor is this one :


Red wire goes from the "063" sensor to the clutch :


At the moment, no power comes to the compressor sensor through the green/blue wire.
(Shorting the two wires does not trigger the clutch)
I just disconnected the red wire going from the sensor to the clutch and connected it to a 12 V source.
 

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Power to compressor clutch comes from trinary switch on top of filter dryer check you have 12v there and if so you have a break in wire to clutch if not work backwards to relay.
 

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If refrigerent drops pressure it will break the circuit to shut down the compressor from damage. The switch( NC) confirms pressure and commonly located on the drier. Shorting these wires will fool the compressor into thinking there is enough in the system...but this is just a test.
Did you put manifold gauges set on the ports?
 
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