Hi Folks,

I have a problem with my AC Blower not working. The relay appears to be functioning (I hear it click when I cycle the fan switch to high setting). I jumped the red wire to to the purple wire that goes to the fan motor and the motor spins up and works fine. I checked the motor speed control with ohm meter and it appears to be in good shape as well.

Reading through the previous posts, there are several threads referring to "check both fuses" or an inline glass 30AMP fuse with a white wire. I don't see any inline fuse anywhere, not sure where in the harness to find it?

Thoughts?

Best,

Paul

 

Futz around with all kinds of wiring diagnostics, checking motor, switches, tracing wires, ohm meters, voltage testing, yada yada. Turns out the flippn connector that goes into the firewall relay doesn't align quite properly. The purple wire which is the hot to the motor never was seating properly. You can't tell this when the relay is mounted to the firewall because you can't see it. However it seats in the relay what seemingly is completely normal. Unless you take the relay off and actually visually inspect the connections, you would never no it wasn't seating properly in the fixture. Wonder how many others have seen this one!

 

 

Additional shot of relay placement on firewall.

 

Thanks for the info idtpes. I've barely started tracking all this down on my 80 myself. So far all I've been able to do it is get the clutch to engage momentarily by connecting a battery straight to it. I also got the blower to blow by doing the same. The system is pressurized some. Jumping the pressure switch does nothing. The wiring is compliments of good ole Bubba himself. I don't know where to go next. The fuse under the dash is good. I think I'll check my relay to see if I have the same problem.

Mike

 

Here is a test procedure I used. Turn your blower switch to high in the car. If you put a jumper wire on the ORANGE to PURPLE wire, assuming you have same color scheme, your blower motor should power up full speed. If it does, than your relay maybe the culprit. Its $12-$15 at Autozone. If it doesn't power up, then jump the RED to the PURPLE, if it powers up, then trace that ORANGE wire down and see where it is leads to, might have a break somewhere. Again, my color scheme may not follow yours, so be careful, don't want u to short out anything.

 

Thanks man, I'll give that a shot!

 

Finally got around to messing with the Vette ac. Purple to orange did nothing. Purple to red ran blower wide open. Looking up o see where the orange wire goes.

 

All the proper wires appear to make it to the fan switch and a/c control. Looking at the schematic in my shop manual I expected to find the orange wire going to to the heater control but but there are only three wires connected to it. another The following wiring diagram I found for 80's verifies that there are only three wires.



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The a/c fuse fits a little loose in the fuse block. There is power to the relay at least since jumping the red and purple wires ran the fan motor but I'm pretty sure that red wire is almost straight from the battery/ starter.

I am looking for a brown wire coming from the fuse block but am not really sure where to look first. Any idea where I can access this wire to check for juice?

 

When you turn cycle the switch from off to high, do you hear the relay click? you might need another person to run the switch while you listen. You should hear it click. If you don't then your relay may not be working. The speeds in between are controlled by the resistor pack that is mounted in the heater core. You can see that resister pack in my second picture. If you haven't replaced the resister pack, I would..it will probably will improve the low/med speeds...it did for me. As for your brown wire...not sure what to say there, my harness has four wires running to the relay...ORANGE wire is what is supplied power to my fan motor. I do have a brown wire, but it goes to the resistor pack.

 

I do not hear a click at the relay. The best I can tell, the brown wire going to the resister is what bypasses the speed switch so the motor runs on low when the key is turned to run.

How can I check for power at the switch and ac function control. Should I get 12 volts there or should trouble light come on when checking brown (or other) wire to ground?

If I'm not getting power at the ends of the brown wire I think my problem may be somewhere before the switches, relays or resisters. Possibly fuse block issue.
Thanks

 

Man, I do not envy you. Wiring / electrical problems are many times a rats nest and can take a lot of time to diagnose and will test a man's patience. If you don't hear a click at the relay when you throw that switch into hi speed, then that tells me you have a bad relay OR; no power running to the relay from the orange wire which is the primary power source for either the resistor pack and hi speed motor function which when in hi speed, the resistor pack is bypassed all together - you can see that bypass in your wiring diagram you posted. So if there is no power to that orange wire it is either a blown fuse, bad switch or the power source leading to the switch is broke / dead somewhere along the path. Some others have indicated in the past that the blower motor is fused in two places...one at the fuse block and there is another "inline" fuse on that orange wire exists some place. In my case, I did not have a secondary fuse - perhaps because previous owner did a bubba wiring job ;-)

My recommendations:

1) I wouldn't mess around trying to figure out the resistor pack right now. I would focus on the orange wire - getting the hi speed function to work first since that eliminates the resister pack all together along with the all the other wires. At that point you are dealing with two wires - orange and a ground - black wire. You already know you have a decent ground because when you jumped the RED to the Purple your motor functioned.
2) Get a volt meter and measure if there is power at the switch when in hi position. If there is not, then you know there is no power making it out of the switch.
3) Then check to see if there is power making it to the switch. If not, trace that wire back to its source.
4) You had mentioned the fuse in the fuse block is loose. If that is the case, you should take a volt meter and measure to see if you have voltage across the two poles of the fuse receptacle. BE VERY CAREFUL doing this, you have virtually no space to work in there and if you short that by accident it won't be pretty. Could be the terminal block where the fuse connects is broken.

Hope this helps.

 

Thanks for all the help. So jumping the the fuse block poles with either a trouble light or volt meter should indicate voltage with key on. I'll check that next!

 

For the moment my blower is functioning correctly in all speeds. I pulled the fuse to check across the poles and nothing. When I went to put the fuse back in I seemed to remember from a diagram a single wire plugging into the front of the fuse block directly above the ac fuse but this fuse had been installed in the slot above. I plugged the fuse in the next spot down and bingo, the fan started working. I had also been poking around the back of the fuse block trying to see the brown wire connection and may have jiggled it back to working. Who knows but for now she blows. Minor victory!!!

 

hey, good news and glad you got it resolved!