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79 Model with A/C - Blower Fan issue

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stuclark:
thanks for the tips, I have repaired the Theft Alarm Switch, so temporarily see how this goes, failing this, off to Jaycar and some mods to their switch. Have just tried to meter out the fan issue. if I put an ohm-meter across the fan winding, I get about 200 ohms, which is probably a bit on the high side? I would have thought much lower than this? I don't suppose anyone knows or could measure across the blower motor winding and give me the ohm reading? I will get under the car again next weekend to see if the starter solenoid wiring issue is there or not. I'm pretty convinced my Relay is shot (5 pin type), Reasonably happy that the speed resistors are ok? but just have some weird wiring up on the firewall that just does not make sense.

Vettech:
Stu - not sure on fan motor resistance - but at full tilt they suck up a bit of juice. at 200π the resultant 60 m/Amps would not be near enough - I remember now replacing mine some years ago (from chevparts Yenora) and it had massive corrosion and rust inside. If you put 12volts on the fan it should run at full speed - no doubt will spark when connected. I don't  have the cct in front of me but would assume the two pins on the relay will be the coil so 12 volts should cause a click here if working. The three pins mostly be a changeover contactor, configured so the power for low and medium go thru it and via the resistors, when operated in high speed power changes over and bypasses the resistors and goes direct to the fan motor. At a guess on high it could drag 10 or more amps. Sorry to sound vague but I have the build book but can't find the manual and cct diagrams. See how you go.

Vettech:
Sorry I just had another thought - should be a connector for hood switch and maybe for AC pressure switch in AC gas line - maybe high pressure  switch. Yes there it is " switch asm - cut off pressure". So maybe that is where another plug thingo  should go.

sabre:

--- Quote from: stuclark on September 28, 2014, 01:47:31 PM ---Have just tried to meter out the fan issue. if I put an ohm-meter across the fan winding, I get about 200 ohms, which is probably a bit on the high side? I would have thought much lower than this? I don't suppose anyone knows or could measure across the blower motor winding and give me the ohm reading? I will get under the car again next weekend to see if the starter solenoid wiring issue is there or not. I'm pretty convinced my Relay is shot (5 pin type), Reasonably happy that the speed resistors are ok? but just have some weird wiring up on the firewall that just does not make sense.

--- End quote ---
Hi Stu. You're right, motor resistance should be under 10 ohms but check you have good test connections before replacing. You could also just run a live to the terminal with the purple wire and see if it runs at full speed. Worn brushes are the most common cause of a high reading
Beware of blaming the relay. The relay only operates when the AC is in 'MAX' position. In all other positions it is inactive with current supplied through the resistor network and the closed terminal of the relay.
The sparking on the black is of concern. Sirfixalot may be on the money as it would be easy to put the earth on the live by mistake although that would cause the autopark of the wiper to misbehave???? It uses the same earth.
I have a full factory circuit diagram for a 78 which should be the same as your 79. What part of the Western Sydney are you in? I'm a little immobile at present but happy to help if you are close.

stuclark:
finally got back to the car and replaced the blower resistor block, just in case, but the problem was in fact the blower relay, now all working fine.

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