79 Model with A/C - Blower Fan issue

[stuclark]

trying to identify where an errant wire goes. I have one black wire that is loose in the engine bay and is part of the wiring harness that seems to feed into the blower fan and also near to the starter motor feed. Pic shows the wire I am trying to find a home for. Anyone with a '79 with A/C that could point me in the right direction I would be grateful. It is not live (black is normally earth) but it does spark if you touch to a ground, so it is completing a circuit. I suspect possibly the blower fan? HELP PLEASE!!!!!

[sirfixalot]

Cant see clearly from the top pic if it goes in the 6 pin plug in the corner with another black wire with a heavy red next to it, it goes onto the factory alarm switch which is located on firewall in second pic

[stuclark]

Hi, sorry, the loose black wire comes out of the 6 pin connector off a terminal with another black wire and next to the heavy red wire wire like you mentioned.

Are you saying this loose black wire should be connected to the plunger switch on the firewall? I cant see where it should connect or join to.

[sirfixalot]

The alarm switch has 2 spade conections. That is where wire goes one on each side.The spade connector may be broken off

[stuclark]

thanks for that, I will look more closely on the weekend.

[stuclark]

thanks, found exactly what you said Sirfixalot for the plunger switch, yes, it had broken away, so now I need to track one of these down. I spent some time also working on the blower fan. Again you were right in that I had 12v to both terminals of the Blower Fan. My Fan Relay seems inoperative, but there is some weird wiring that someone has done in and around this area. I'm pretty much at the end of my capability now, so thinking I might need an auto sparky? Know any in the Western Sydney area that might do house calls?

[stuclark]

So after some investigation this is where I am up to and now stuck. Hoping I find someone with a stock '79 with A/C that I can either get some pictures off or go to look at the wiring to compare. but the attached might help show my situation

[Vettech]

Stu - the switch looks like a generic and should be available from any Auto store  that sells alarms - may be Jaycars.
I'm  in the W/subs but I'm  as sick as a dog at present and my 78 is currently doing an impression of a storage cabinet and getting into the motor would be tricky - I'll  have a look at my build book and maybe find my manual. If I find some info I'll  let you know. Oh and I have gear to test any electrical bits etc.

[sirfixalot]

Check down on the starter to see if the black wire has been installed onto the 3/8 stud on solenoid is a common fault on fan motor which puts + on both sides of fan motor if it is on the stud remove it & put it onto the bell housing bolt . Disconnect purple wire off fan motor & operate fan switch connect a test lite to earth & you should be able to see the speeds.I have the male / female 6 hole plug brand new give me a call. may even have 2nd hand switch, Jaycar have a similar switch you will have to connect second wire under the mounting nut as it is above earth potential mounted on fiberglass

[Vettech]

Not sure if I'm helping as my cct's etc relate to 78, but it's relay has five connections - a two pin plug on two and a three pin plug with one pin offset on the other three. A seperate plug comes out of the loom and goes to the fitting that carries the speed resistors mounted thru the AC housing. Even though mine has been converted it was done back in 79/80 and the Blower housing/Evap assembly is still on the RH side.  There is another two plugs out of that loom but the pages don't  show everything.

[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]

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.

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.