boecherer

I just saw a response to this post and saw what I wrote and that I would update this when I checked the fuse box connections. That was back in 2020 and since then I did check the fuse box. I disconnected it and took it apart a bit and found sone of the leads that mate with the relay for the blower motor were not making a connection. I was able to coerce them into making a better connection and the fan has been working ever since

It did get stuck on high (4) recently and that was due to the resistor module that goes bad and doesn't provide any resistance so all fan positions are stuck on high (no resistance). The funny thing was that I replaced that module with a replacement a while back trying to troubleshoot the blower issue and it turned out not to be the issue, but I left the replacement in since it was in and done. So when the fan got stuck on high recently, I knew what it was and I put in the original module that came with the car and that worked. Nice to have spare parts laying around and ones that are original and older than the replacement parts.

66mustangcoupe289

i’m having the same issue, ive replaced the blower motor, blower motor resistor, ac clutch relay, blower motor fuse, im getting power to all the connection, sometimes it blows and works fine sometimes nothing blows at all im lost i dont know what else it could be other than ground or pcm issues

66mustangcoupe289

also have a new power distribution box(fuse block/box) whatever you wsnt to call it

boecherer

Sorry to hear you're having so many problems after replacing just about everything. Someone above mentioned the actual fan switch (in the dash I assume) might be the problem. Have you tried replacing/checking that? Maybe you can bypass it to see if it stays on when not using the actual switch.

When it blows does it blow at the correct speed or only high speed? Since you've replaced the resistor it's probably not that since even if it went bad again, it would blow at full speed.

66mustangcoupe289

yes when it blows everything works correctly, however it is more likely to cut off if keep touching the controls

boecherer

It sounds like it might be the switch. Someone mentioned above "I have helped with many blower problems and it tends to be the connector on the fan switch itself that cannot handle the fan/resistor currents without overheating and loosing all connections." if you haven't seen that. There is also a schematic: https://iihs.net/fsm/?d=40&f=Manual%...l%20System.pdf

I'm not a mechanic, but I've fixed a lot of things. I would try messing with the switch and continually switch it to see if it's reliable. From the info above, if the switch can't handle the fan currents without overheating, I assume that when the fan is on the highest speed, the most power is running through the switch.

And not knowing what the switch is like, maybe you can get it out and set something up to set it on speed 2 or 3 by bypassing the switch to see if it runs longer without the switch in the mix.