nlcrane wrote:Both relays are pin compatible and can be inadvertently interchanged. The dark blue relay (Hella 4RA 003 510-34), however, has our old friend the quench diode internally mounted across the relay coil terminals, this is to quench the reverse emf caused by the collapsing magnetic field on de-energizing and to prevent this reverse current from damaging any downstream components. The light blue relay (Hella 4RA 003 510-68) has no diode, but has a current limiting resistor mounted in place of it.
My guess is that the diode had shorted, so the relay could not energise and so the clutch couldn’t be pulled in.
abercanadian wrote:Sorry can't check the colours because I don't have the original relays any longer.
After going through some electrical issues a few years ago, I found that the Hella light blue relays were the subject of a Jaguar bulletin so I replaced them with the recommended black sealed relays.
The bulletin posted below will also clarify the use of the various relays.
pimgmx wrote:Another known weak link in the A/C chain of late model years is the so-called trinary switch, replacing that solved the A/C issues on my early '94 Sovereign and late '93 Insignia...
I'd suggest to check for leaks for first, though, before you start replacing parts that might still be OK!
abercanadian wrote:A good way to check for a leak is to pick up a UV LED flashlight - (there are some really good ones on eBay for not too much money)
Try to take the car into as close to total darkness as you can and start shining the light into the engine compartment. Shine it along the a/c hoses, ports, unions, compressor and through the grille to the condenser. If you have a leak you should see the leak point glowing brightly from the trail of dye that has escaped from the system.
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