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On my 75, the High fan speed does not work (other speeds do). I read where if this is the case the relay is bad. Replaced the relay and still no high speed. Any ideas?
Check to see if you have 12 volts at the relay that feeds the blower motor. I think the power comes directly from the horn relay and has a fusible link in the wire
My 76 had the same problem. My relay is located on the passenger side under the hood and is attached to the air box. I found my fusible link by tracing back from the relay. In my case the fuse had blown in addition to the power wire being no good, replaced both, then relay died. Replaced relay and the new POS one burned up as well. I decided to replace with a modern relay and changed it's grounding point. Not only does it work but I have better voltage which makes the fan actually blow stronger. 👍
If your blower is not working on the High setting the first place to look is the 30 Amp fuse at the driver side fender.
Circuit #40 ORN wire from inline 30amp fuse (driver side fender area) is the common side of the high speed relay.
1) Place blower switch to high, if you have 12V on DK BLU wire at blower relay than the switch is good.
2) With blower switch to high check for power at the blower relay ORN wire, if you have 12V the fuse is good.
3) With blower switch to high check for power at the blower relay PPL wire, if you have 12V the relay is good.
Outside of wire issues there are only 4 components in the HI Blower system. 1) Console switch, 2) 30A Fuse, 3) Blower Relay and 4) Blower Motor.
If the blower motor is working on lower settings the motor is good.
If your blower is not working on the High setting the first place to look is the 30 Amp fuse at the driver side fender.
Circuit #40 ORN wire from inline 30amp fuse (driver side fender area) is the common side of the high speed relay.
1) Place blower switch to high, if you have 12V on DK BLU wire at blower relay than the switch is good.
2) With blower switch to high check for power at the blower relay ORN wire, if you have 12V the fuse is good.
3) With blower switch to high check for power at the blower relay PPL wire, if you have 12V the relay is good.
Outside of wire issues there are only 4 components in the HI Blower system. 1) Console switch, 2) 30A Fuse, 3) Blower Relay and 4) Blower Motor.
If the blower motor is working on lower settings the motor is good.
I checked these according to your instructions.
I did not find a 30 amp fuse on the drivers side, but will look some more. There is a 30 amp in-line fuse (org wire) going to the relay that is good. I unplugged the relay switch and checked the connections on the harness as you said. #1 had 12V. #2 had 12V. #3 (purple) did not have 12V. Should I have checked it with the harness plugged in? It is a new relay. Blower does work on all lower settings. Thanks!
Last edited by ALLEN007; Jul 13, 2023 at 08:55 AM.
Yeah, I believe I got it. After not having power to the purple wire as MR D. instructions said it should have. I found another post on here from 2003 where the guy jumped a wire from the Orange to Purple wire and his high speed fan worked. He said they sold him the wrong relay. I did that to mine and it worked. So I guess my issue now is to figure out why the purple wire does not have 12V. The purple line has limited voltage as the switch changes positions, until it gets to the high. On high, the purple line has no voltage. Or do you think I have the wrong relay as well? This site is awesome. Thanks all!
After doing a it more research looks like I do have the correct relay according to some parts sites I looked at. # JD191K16-12V
Last edited by ALLEN007; Jul 13, 2023 at 11:21 AM.
My issue was the 50 year old plastic plug that was not making a good connection with the spade relay terminal for “ the High Speed.” It took me buying a new relay and fan switch before I stumbled on the real cause. Don’t you just love these old girls?
I checked these according to your instructions.
I did not find a 30 amp fuse on the drivers side, but will look some more. There is a 30 amp in-line fuse (org wire) going to the relay that is good. I unplugged the relay switch and checked the connections on the harness as you said. #1 had 12V. #2 had 12V. #3 (purple) did not have 12V. Should I have checked it with the harness plugged in? It is a new relay. Blower does work on all lower settings. Thanks!
Yes, you need to have the harness and relay connected to perform this test, probe the back of the plug for power.
You stated that you had 12V at the ORN wire so that rules out the 30A fuse in the system being the problem. Next up is when the blower speed switch is placed in the High position it completes the circuit between (directs a 12V signal) the blower switch and the AC Relay via the DK BLU wire. When this happens the coil inside the relay is energized creating a magnetic field and pulling (closing) the contact that has 12V at the ready on the ORN wire. When this happens 12V is directed from the ORN wire contact to the PPL wire that feeds a full 12V to the blower motor.
When the blower speed switch is placed in the M1, M2 or LO position 12V is directed to the Resistor that reduces the voltage coming out of the Resistor to the Blower Motor causing it to operate at a lower speed.
With the Ignition switch in the run position, blower motor switch in the HI position you should have 12V at the ORN wire, DK BLU wire and PPL wire. If the PPL wire does not have 12V the relay is not closed. Have you verified the ground connection at the relay is good? This will prevent the DK BLU wire circuit from being completed.
Yes, you need to have the harness and relay connected to perform this test, probe the back of the plug for power.
You stated that you had 12V at the ORN wire so that rules out the 30A fuse in the system being the problem. Next up is when the blower speed switch is placed in the High position it completes the circuit between (directs a 12V signal) the blower switch and the AC Relay via the DK BLU wire. When this happens the coil inside the relay is energized creating a magnetic field and pulling (closing) the contact that has 12V at the ready on the ORN wire. When this happens 12V is directed from the ORN wire contact to the PPL wire that feeds a full 12V to the blower motor.
When the blower speed switch is placed in the M1, M2 or LO position 12V is directed to the Resistor that reduces the voltage coming out of the Resistor to the Blower Motor causing it to operate at a lower speed.
With the Ignition switch in the run position, blower motor switch in the HI position you should have 12V at the ORN wire, DK BLU wire and PPL wire. If the PPL wire does not have 12V the relay is not closed. Have you verified the ground connection at the relay is good? This will prevent the DK BLU wire circuit from being completed.
I promise you I had 12V to the orange wire the last couple times I checked it. This morning, no power to the orange wire. Anyway, the culprit was the in-line 30 amp fuse. If you wiggled it was hot, wiggle it again and no power. Anyway, got a new in-line fuse and all is good. All speeds work. Not as much air as I would have thought but I guess that's because it's 48 years old. Thanks everyone for all the help! If nothing else I now know all about how this portion of the AC works.
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No Hi speed on AC blower
