Blower fan not working

[Evans Ward]

Have an 87 GMC Sierra Classic- I do not have any blower fan blowing at any of the speed switch settings. Switch is also new. Can someone point me in the direction of what to check in order of trouble shooting? Thanks in advance.

 

[Boonie]

My 74 has an inline fuse under the hood up by the firewall. Passenger side. I don't know if they still have that in 87 though.

 

[Evans Ward]

Mine keeps blowing the AC/ Heater fuse in the fuse box under driver side floor area immediately as soon as put in.

 

[chengny]

I assume (being from GA) it's with A/C.

Does the fuse blow instantly even with the selector lever (i.e. the vent/mode control, not the fan speed switch) all the way over to the left - in the OFF position?

If so, the short/ground is in the wire between the fuse block and the HVAC control panel.


It doesn't happen often, but sometimes the blower resistor shorts out internally (usually they just go open) - pull it and inspect the resistor coils. It is located here:

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If you don't have one, you should by a multimeter. Shotgun repairs on these trucks is not a good idea. The parts are expensive and hard to find.

When I say "shotgun repair", I mean just changing part after part in the hope that eventually you will change the one that is causing the problem.

 

[Evans Ward]

Thanks and I will check that out and report back at a later date.

 

[BigPoser]

I have the same problem as well. Heater works, but blower fan doesn't turn on at all. I have that inline tube fuse and it's good.

Would the resistor coils be the root of my problem as well?

 

[smoothandlow84]

Check the ground wire for the blower fan...in the rust belt states, it seems to be a common problem. Have you also tried running a jumper wire from the power plug of the blower fan directly to the battery? It could also be the blower fan relay switch. On my 87...its mounted on the fan housing close to the firewall. If a meter indicates power into the relay, but no power out...its the relay. New relays are under $30.

 

[BigPoser]

Check the ground wire for the blower fan...in the rust belt states, it seems to be a common problem. Have you also tried running a jumper wire from the power plug of the blower fan directly to the battery? It could also be the blower fan relay switch. On my 87...its mounted on the fan housing close to the firewall. If a meter indicates power into the relay, but no power out...its the relay. New relays are under $30.

Ha, yeah i did that last night actually and the blower kicks on. I remember that when I rewired my truck, there was a wire that was left unplugged on the AC control. I think that it might be for the fan switch. Not sure why the new kit didn't have it, but all it had as the wire to power the system. It's cold and I gotta get this working soon.

 

[Greybeard]

If you just want heat while you are troubleshooting the real problem run a heavy wire from a hot terminal of the fuse box (Or battery if you feel lucky) through a heavy switch or switched relay, to the power in of the fan, at least you will have a blower on one speed to move the air around.

 

[BigPoser]

If you just want heat while you are troubleshooting the real problem run a heavy wire from a hot terminal of the fuse box (Or battery if you feel lucky) through a heavy switch or switched relay, to the power in of the fan, at least you will have a blower on one speed to move the air around.

Got mine to work, although when on the highest setting it stops working. Maybe the relay or resistor. Good to have heat again.

 

[hatzie]

No HI is usually either a bad relay or no power to the Relay common from the J-stud on the firewall.

 

[wczimmerman]

Got mine to work, although when on the highest setting it stops working. Maybe the relay or resistor. Good to have heat again.

I have an 87 Suburban that will turn the blower on at all the speeds (usually) but it will then stop blowing until I switch to a lower speed. At first it would only do it on HI, then it started doing it on HI and the next step down. Now, occasionally, it won't even turn on but if you leave it while you drive it will kick on at some point. Any pointers? I was planning to replace the A/C controls but after reading this thread I am reconsidering.

 

[chengny]

A good place to start would be to check the condition (and terminal connections) of the blower ground strap. Because the blower motor is mounted to a plastic housing on A/C equipped trucks, there is no path to ground via the motor casing (as there is with a heat only blower - which mounts to a steel housing).

To create the ground path an external wire is used. It runs from a screw located in the upper inboard section of the motor housing over to a big screw that threads into the firewall:

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Electrical components that exhibit erratic operation (but are not completely dead) often simply have grounding issues.

 

[89Suburban]

The fan speed switch also burns up inside and causes intermittent operation. You may even see burn marks and carbon right where the harness connects to the switch.

 

[wczimmerman]

I found the issue: when GM built the truck, they ran too many wires over the harness for the temp/heater selector (the slide for A/C, vent, defrost, etc). Consequently, the plug was weighed down over time causing a short or light contact situation. You can see from the attached pics the switch was burned badly. There is still an issue with the plug itself but I have that "remedied" by re-routing the wires to remove the load and by taping the wiring for the fan selector and this selector switch to the inside of the dash for extra support.

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