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Mainframe444
18th April 2015, 12:12
A few observations that might be helpful to members.....

My Connie CDT Tourer had a failed engine fan and no air con as bought.

Whilst repairing these items, the following was found.....

My car had a dead three speed fan (probably brushes!) so I acquired a replacement two speed unit (and fitted one of Jule's resistors first!)

This is plug and play, there is no need to modify any wiring.

The demister test described on here will only work if the aircon is in working order, when the new fan was fitted it would not work in demist, but I knew it was ok as I had tested it off the car. Once the aircon was regassed the fan worked when the demist test was tried.

The aircon appears to have failed due to a rotten condenser, once the old fan was removed a lot of the fins were missing, and though I could not see any holes in the bits with gas in, I assume this was where it had evaporated from.

If your car has non-functional air con and you want to test the fan, unplug the Trinary Switch and connect the pin with the Yellow/Grey wire to the battery earth with the ignition on. The fan will run at slow speed if it is working.

Hope this is of some use, I now have nice cool air con and a working engine fan, just need to sort the thermostat now so I have the correct running temperature!

T-Cut
18th April 2015, 15:56
The trinary switch inhibits the fan if the refrigerant pressure is too low to run the aircon system.

You're right about the trinary switch.
Trinary test method: http://www.the75andztclub.co.uk/forum/showthread.php?t=35567

TC

SD1too
18th April 2015, 19:42
Thanks for your helpful thread Paul, but all readers should note the following:
The demister test described on here will only work if the aircon is in working order ...
This is true only with the diesel engine.
If your car has non-functional air con and you want to test the fan, unplug the Trinary Switch and connect the pin with the Yellow/Grey wire to the battery earth with the ignition on. The fan will run at slow speed if it is working.
This is incorrect. The trinary switch test described will trigger the medium speed on a 3 speed fan system and the fast speed on a 2 speed (with resistor) system.

Simon

SD1too
18th April 2015, 19:47
The trinary switch inhibits the fan if the refrigerant pressure is too low to run the aircon system.
TC
That's not quite right TC. If refrigerant pressure is below the low threshold, it's the compressor clutch which is disabled by the trinary switch.

Simon :}