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Originally Posted by White horse
had a look at the fan, 4 wires leave the control box and go in to the fan, would that be a 3 speed fan?
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Yes, you have the earlier 3-speed system.
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The fan control box has three relays(?) inside. I have disconnected the wiring to the fan, the piggy back job on the chassis rail, if I reconnect that and try the demist test I should hear one of the relays click, would that be right?
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All else being in place, yes. The relay should trip power to the (slow speed) fan. The usual cause of this problem is failure of the motor brushes.
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Also, no sign of a resistor, the usual mounting point shows no evidence of holes ever having screws in them. More evidence of a three speed fan?
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Yes, the resistor is only present in the later 2-speed system. The fan guard bracket is there but it won't ever have had a resistor on it.
You have two options. Try to rebrush the motor or replace the whole shebang with a later 2-speed system (or the aftermarket alternative), including control box (all plug and play).
If the fan tests failed to run the fan at any speed at all, then I reckon your chances of recovering the old motor are pretty slim. Examine the commutator if you fancy a go.
There's a Howto rebrush the motor and recommended suppliers if you do a key word search using the Google based search system:
https://cse.google.co.uk/cse?hl=en&c..._YDw#gsc.tab=0
TC