Heater Power Issue/Question

[TheRedMamba]

Babygirl is a mistreated 1993 GMC Sierra SLE Extended Cab K1500 4x4, Z-71, 5.7L V8…

A few days ago the blower fan went out, the plastic fan was detached from the motor, because of location the new motor with fan attached took a couple days to arrive, It's averaging a -8 here at night, I sleep in my truck, easier for work, so I tried a quick, temporary hack job of reattaching the fan to the blower motor. It worked for like an hour when the actual motor finally went.

Issue:
When the motor finally died the control head went dead and there was a slight smell of melting plastic…. Like wire insulation, etc. but only for a minute, I was also pushing the fuse back into the fuse box when the power supply died and I noticed the smell.

I replaced the blower motor, brand new with the fan attached.

Nothing. Still no power to control head.

Sidenote: When the blower initially stopped working, the Heater Control Head had power until reinstalling the fuse.

Went to the yard and pulled a Heater Control Head out of a 1994 Silverado, installed and no change.

I do not see any melting damage on the wiring behind the fuse box or the harness that attaches to the Heater Control Head. I haven't checked elsewhere other than fuseable links under the hood at the bulkhead Distribution Block (Passenger Side).

Does anyone know if the Heater has a fuseable link somewhere I can check?

Any ideas on where to find the most likely spot where my issue might be?

Any help/suggestions would be great and appreciated! It's freaking freezing! Lol I'm a decent, fairly knowledgeable home mechanic, but electrical is not my strong point.

I'm off work tomorrow and will begin tracing the wiring visually and with my multimeter!

I do have the 1993 wiring service manual but I'm not finding an exact schematic for the heater, just the blower and AC!

TIA! I Appreciate it! Cheers

 

[movietvet]

If you smelled it, only for a quick time, there was already damage being done. You need to track all related wiring and connections. Is there not a blower resistor? I am unsure of the location. Not seeing melting/damage does not mean there is none. Inspection of all connections is needed. Sometimes, just disconnecting and reconnecting is enough to clean a connection.

 

[TheRedMamba]

Thank you. With the down time I have today that is the plan. Cheers

 

[GoToGuy]

Do you have the OE service manuals , not Haynes or chilton. If you don't in the sticky above is the link for your year, the forum library has many. In it it has the details of fan and heater operation. If you smoked the fan speed resistor, it will have to be replaced. It's in area below glove box. Also the connector at fan is prone to overheat , fail.

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[TheRedMamba]

Do you have the OE service manuals , not Haynes or chilton. If you don't in the sticky above is the link for your year, the forum library has many. In it it has the details of fan and heater operation. If you smoked the fan speed resistor, it will have to be replaced. It's in area below glove box. Also the connector at fan is prone to overheat , fail.

You must be registered for see images attach

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I do have the 1992-1994 manuals downloaded from this forum, there only the wiring for the 1993. Let's say the resistor is smoked, would that be the cause of the control until not having power?

 

[GoToGuy]

There shouldn't be much difference between 93-94,
You have this 94 manual, it's in section 8A- 60 starts with heater controls etc. the power, grounds, locations, digrams.

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[TheRedMamba]

Babygirl is a mistreated 1993 GMC Sierra SLE Extended Cab K1500 4x4, Z-71, 5.7L V8…

A few days ago the blower fan went out, the plastic fan was detached from the motor, because of location the new motor with fan attached took a couple days to arrive, It's averaging a -8 here at night, I sleep in my truck, easier for work, so I tried a quick, temporary hack job of reattaching the fan to the blower motor. It worked for like an hour when the actual motor finally went.

Issue:
When the motor finally died the control head went dead and there was a slight smell of melting plastic…. Like wire insulation, etc. but only for a minute, I was also pushing the fuse back into the fuse box when the power supply died and I noticed the smell.

I replaced the blower motor, brand new with the fan attached.

Nothing. Still no power to control head.

Sidenote: When the blower initially stopped working, the Heater Control Head had power until reinstalling the fuse.

Went to the yard and pulled a Heater Control Head out of a 1994 Silverado, installed and no change.

I do not see any melting damage on the wiring behind the fuse box or the harness that attaches to the Heater Control Head. I haven't checked elsewhere other than fuseable links under the hood at the bulkhead Distribution Block (Passenger Side).

Does anyone know if the Heater has a fuseable link somewhere I can check?

Any ideas on where to find the most likely spot where my issue might be?

Any help/suggestions would be great and appreciated! It's freaking freezing! Lol I'm a decent, fairly knowledgeable home mechanic, but electrical is not my strong point.

I'm off work tomorrow and will begin tracing the wiring visually and with my multimeter!

I do have the 1993 wiring service manual but I'm not finding an exact schematic for the heater, just the blower and AC!

TIA! I Appreciate it! Cheers

I think I found the problem...

There shouldn't be much difference between 93-94,
You have this 94 manual, it's in section 8A- 60 starts with heater controls etc. the power, grounds, locations, digrams.

You must be registered for see images attach

I do thank you

 

[TheRedMamba]

This might be the problem eh?!! Ugh!!

 

[Caman96]

This might be the problem eh?!! Ugh!!

That may be the result of an issue and not necessarily the cause.

 

[movietvet]

That may be the result of an issue and not necessarily the cause.

Like a head gasket failure is usually the result of another problem. I agree, fix and fire it up and be ready to do further tracking.