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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.

  • I'd remove the blower and test-run it. Build a test-rig with a battery, some test-leads, a matching fuse and a checked resistor. Perhaps you have seized bearings, worn coals or faulty cabling. – Martin Jan 11 at 16:03
  • Thanks Martin. do you know of any any tutorials on how i can build a test rig? – Allan Varkey Jan 11 at 21:42
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When it only works on high, this is a sure sign the blower resistor is blown. The resistor "does work" at the slower speeds by limiting the power which will flow through. It's direct power on high speed. When the resistors fail, no power at all goes through these. This is a very common problem on GM vehicles when they get a few years on them.

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    Bad motors damage resistors, I always replace both the motor and resistor when the resistor is blown. – Moab Jan 11 at 16:49
  • so i changed my blower motor and my resistor between two days apart. it ran fine for two months. however the position before high was not available a week after the motor was replaced. i didn't care much because all the other options worked.this issue of intermittent blower motor engage started happening beginning this week . is it safe to say that the blower motor is not wrecked? – Allan Varkey Jan 11 at 18:30
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    @AllanVarkey - If it blows, it blows. As far as the resistor, you may have just got a bad one. More than likely, depending on where you got it at, it should still be under warranty so replacement should be free. – Pᴀᴜʟsᴛᴇʀ2 Jan 11 at 19:12
  • @Pᴀᴜʟsᴛᴇʀ2 Thanks Paul, ill try swapping out the resistors and see if that makes a difference. – Allan Varkey Jan 11 at 21:42
  • @Pᴀᴜʟsᴛᴇʀ2 i updated the question with an update. it didn't work after swapping the resistor – Allan Varkey Jan 14 at 19:06
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We sorted out the issue. The problem was the connector to the speed control switch in the cabin. It was fried up. once we swapped it out , it works like a charm. Thank you all for the answers and tips.

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