Trying to sort some wiring nightmares on my friend's '69 H/O (A/C car). Someone cut the wires to the high speed fan relay and discarded the relay (even sloppily filled the holes behind the booster!). We repaired the wiring with the correct ends and connectors and replaced the high speed relay. Blower works on 'High' speed only. I assumed the resistor was bad but when I pulled it out all the coils are intact and not burnt. I have no power to the resistor connector when lower speeds are selected. Before I pull the fan switch to check it, is there anything I'm missing? The only other thing is the relay we replaced behind the booster is of unknown origin but the prongs were configured correctly so we used it (it may be the problem).

 

There is an inline fuse under the hood for the blower. It's on the drivers side and runs from the horn relay to the blower relay you worked on. I think it's a blk wire w an orange stripe + it's a fat wire. Maybe 10-12" from the horn relay it's built into the wire + pulls apart. Usually when that goes you get no hi speed, but all the other speeds work, but it's worth looking at.

 

Please post a picture of the relay and plugs (disconnected) - I am betting that direction. You need a single pole double throw relay to make it all work right.

Correct relays can be had from local parts stores and Rockauto.

 

I did check the Black/Orange stripe fused wire from the horn relay and have good continuity to the high speed relay. High speed is all I have no other speeds.

 

what other wires do you have going to the relay?

 

Black/yellow stripe goes to the single terminal and the 30a fused 12v feed, purple and blue wires are grouped together on the 3-prong with the 12v feed on the engine side, the purple in the middle and the blue on the firewall side as looking at the relay. I think I'll try another relay since they're less than $10 and, like I said, the relay we used is of unknown application. I assumed they were all the same.

 

There is really no mention of the 'High Speed Fan relay' in the repair manual and schematic so it's hard to figure out the sequence of events. If the Black w/ Yellow stripe wire comes from the switch does that mean the other wires from the switch (lower speeds) go through the resistor first? I understand the 'High' speed bypasses the resistor hence the need for it's own relay. The 'Hold-off' relay on the passenger fender seems to be working normally (which was something else that was missing that we replaced earlier). A/C compressor comes on with switch and stays on even after switched off until ignition is off which is correct (some anti-dieseling thing I think). I suspect the fan switch on the dash because I have no power to the resistor when the lower speeds are selected.

 

Here is a good thread for ya - I knew I remembered going through all this before!
https://classicoldsmobile.com/forums...y-mystery.html
A/C wiring is in the A/C section at the front of the CSM...

 

Thanks Rob. So according to that schematic 'High' speed terminal on switch goes directly to relay behind the booster. All other speeds go through the resistor FIRST then the relay. Since I have no power to the resistor on the lower speeds the problem has to be between the fan switch and the resistor.

 

I know you said the resistor looks good, but sounds like that could be the issue. Test continuity before/after the resistor to see where you have power with the switch on the low speeds.

 

The lower speeds use a different power source...look on the fuse block for the heater fuse and follow it to the switch...

 

But that power source drives the relay for high speed. If the relay is energizing, then the fuse in the fuse block is good.

Check all connectors for burns or discoloration - clean and or replace terminals as needed.

 

I realized that after I posted ...so it has to be in the harness from the switch to the resistors...