ZX Heater Puzzle

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Ginganav
Posts: 4
Joined: 25 Nov 2002, 22:01
Location: United Kingdom
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ZX Heater Puzzle

Post by Ginganav »

Hi Folks, any electrical experts around I would appreciate some help:
Heater on 93 1.9 TD ZX failed instantly, switch and motor checked, seem ok. Resistor checked and with multimeter and there seems to be no resistance at all between 'output' connector and 4-speed 'input' connectors so a new one fronm Andyspares reveals logical increase in resistance at 4 'speed' connectors. Also now getting 12v between both red and black blower motor connectors, BUT THE MOTOR WILL NOT TURN. Motor turns fine when connected directly to the same battery so figured it might be the blade connectors which were removed and wires connected directly to motor. This at least gets motor turning v slowly and at same speed regardless of rotary fan switch setting. Before I give up totally and pay an autoelectrician, what else can I check to get my heater back to normality, this snag is taking up far too much of my time and I'm pretty clueless when it comes to wiring diagrams. Could it possibly be that I'm not getting the requisite current thru' despite having 12v at the motor supply any speed?
Would appreciate anybody's help on this, it's doing my swede in!
David W
Posts: 439
Joined: 30 Apr 2001, 17:49
Location: United Kingdom
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Post by David W »

David,
Just changed the resistor pack on our 1993 ZX TD, and done loads before.
I think it all works like this...
There is a 12v supply to the motor all the time the ign is on. The other motor lead goes to earth via the resistor pack and speed switch.
If you take the multiplug from the resistor you should be able to find the 12v feed from the motor (yellow wire?). Also you should be able to find the direct path to earth for full speed (blue wire?). If you temp link these terminals on the plug with the ign and blower switched on the fan motor should run quickly.
If it seems slow there must be a high resistance somewhere, these motors draw a fair current and need sound connections.
To prove the fault is in the earth path from the resistor plug to the car body via the speed switch take a temp wire from the 12v feed side of the resistor plug to any sound earth point. If the fault is in this section you will regain full speed.
To test for a poor 12v supply run a temp 12v supply from the battery to the 12v side of the motor with the bridging wire over the blue to yellow terminals (assuming those colours were correct) as above. If you get full speed now start looking for a high resistance joint in the feed via the fuse and ign switch...in fact check the fuse ends for corrosion first.
I hope this reads as I understand the system. It is harder without the car and test meter in front of you!
David
Ginganav
Posts: 4
Joined: 25 Nov 2002, 22:01
Location: United Kingdom
My Cars:

Post by Ginganav »

Thanks for that DJ, I'll give it a go tomorrow.
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