I have an 1989 s10 with a 4.3 l V6. I am having some trouble with the AC blower motor. In winter when I start my truck and switch on the heater or vent and slide the blower motor. It only kicks in at high. I've also noticed that at times the blower shuts down and restarts .sometimes it doesn't even work and the operation has been very intermittent. In the last 2 months I've changed the AC blower resistor, the as blower speed control switch in the cabin, the blower motor fuse and the heater core. Can someone tell me how I can diagnose and find the problem? Has anyone else faced a similar issue?
Update Jan 13 2018
Installed a new blower resistor, however it didn't work. I also noticed that when you switch to any speed mode, there is a faint amount of air being blown through the vents. However its not strong enough to warm up a vehicle for the harsh Alberta Winters. Does this mean the blower motor is kaput?
Update on blower motor behavior - Jan 15 2018
This is interesting, the temperature dropped to -8 in the morning. when i started the truck and switched on the heater , the blower motor kicked in. However after driving it for a bit , it shut off the motor. When i placed my hand on the vent, i could feel a faint amount of air flowing through.