I am working on a new to me 1969 XR7 with factory A/C. The blower motor is not working for me to fix the air conditioning. Fuses are good. I want to drop 12v directly to the blower. Do I access the blower motor wiring from the driver’s or passenger side? I assume if the blower works with 12volts, then the blower switch is the next spot to check, or should I drop 12 volts to the resistor?
Once I get to blower working what are the items to check to get the compressor clutch to engage? It does have low pressure, so do I start charging and will it engage when a specific pressure is obtained?
Normally the blower motor switch is the culprit. See if yours is bad by using a multimeter. The compressor clutch should be on anytime the AC switch is on.
Like Royce says, there is no low pressure switch to keep the compressor from engaging anytime the AC switch is on. The only other thing that can disengage the compressor is the icing switch at the evaporator coil. That is what causes your compressor to cycle off if the evaporator coil gets below freezing. But it should be closed allowing the compressor to turn on when you first turn on the AC unless it’s below freezing inside your car. I’m not sure if the icing switch is a high failure item or not.
To check clutch , just un plug at the compressor and jump 12v to the plug. By the way , my whole dash got happier when adding relays for the ac clutch and high and lo beam that I mounted by the core support near the regulator. All the signal wires are right there.
I have a similar issue on my new to me ‘69. I wanted to check the fuse, but I’m not sure where it is. When the interior was being restored by the previous owner and the dash was out, there is video of the fan + switch working but now I get nothing so I’m now starting the long road of troubleshooting.
I’ve been tearing into mine this week. Thanks for the photo of the fuse box. I found the wiring diagrams can be downloaded for free from the West Coast Classic cougars parts page as a free purchase.
I pulled all the center bezel and radio out and undid the plug to the back of the switch. When the key is on the accessory position there is no power to any of the wires going to the fan switch. I verified all the fuses are good and have power across both ends with the key on.
So it seems I have an issue in the wiring between the fuse block and the plug. The wiring harness is really hard to get to so I need to figure how to get access to trace it.
If I’m reading the wiring diagram correctly, it’s the heavy gauge yellow wire marked as circuit 257 and it goes straight from the fuse block to the switch.
Unless you are a lot luckier than me, you will probably have to pull the dash pad to trace that heavy yellow #257 wire. At least now you know which one to trace.
The fuse box in my picture is not normal. Most of them have terminals so rusty that no contact between the fuses and the terminals is possible. Normally you have to remove the entire wiring harness to be able to remove the rust from the fuse panel. It can be done by soaking the panel in Evaporust or mechanically removing the rust with a Dremel and a wire brush.
I’d be careful using Evaporust (or any other liquid) by soaking with wiring, as it can get inside the insulation and possibly damage the copper wires. I tried it on rear lamp sockets, and I didn’t like the results. My preference for fuse clips is to sand-blast the clips, then spray Boeshield T9.
So I decided to recheck all the fuses because it does not make sense that the wire loom would suddenly have an issue, especially with that heavier gauge wire.
When I checked the fuse again with the probe it seemed a little intermittent and I thought it was a bad ground but when I pulled the fuse out, the end cap fell off. Seems it was blown up behind the end cap and the end cap was loose. When I would push on it with the tip of the probe there was something making enough contact most of the time that it would seem to be working. I swapped the fuse and I now get constant power to the fan switch.
When in doubt replace the fuses I think is the motto. Also I think the fuse that was in there was a smaller amperage than should be there with AC.
DrDesoto, can you take a photo of how your relay wiring routes for your A/C clutch? My 69’s clutch wire runs from harness through firewall down the driver’s side of intake manifold in a couple of clips along valve cover (351M) to the compressor clutch. Did you loop it just before the clutch then across front of motor above timing cover/water pump over to the regulator panel and mount a relay by the regulator, than back across to the clutch?
Scott and Kyle recently helped to get my a/c revived again after being kaput for 20+ years. Discovered like Royce stated, the little micro looking compressor switch on the blower switch was shot (along with a broken a/c lower box from a botched earlier heater core replacement, and more issues).
I’m debating on putting all my AC stuff back in Greeny someday. What are we talking $$$ wise??? And is there enough stock stuff around to put all back to factory (appearing)???
