AC/Heater blower motor does not work on high

[Charlie]

Had this issue the past few days The blower motor shuts off when switched to high. Works on all other speeds. With the help of a squarebody guy, issue resolved.

There is an orange 10 ga wire on motor relay that goes thru harness to firewall that has an inline fuse connected to the junction block. The fuse holder/fuse was burnt. Replaced fuse holder, now have the high speed on blower. This wire has a constant 12v.

Using AC lately has been bearable in our Texas heat, I could use the bi-level setting and the medium 2 fan speed.

There may be some here that has had this issue and there may be others that this could help.

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[Big Chip]

 

[Charlie]

Thank you very much. Good to know that someone is noticing my posts!!!

 

[bucket]

Was it a factory fuse holder? My '77, '78 and '79 don't have a fuse holder and the junction block is over towards the driver side of the firewall.

 

[Charlie]

Was it a factory fuse holder? My '77, '78 and '79 don't have a fuse holder and the junction block is over towards the driver side of the firewall.

Yes as far as I know. Truck is mostly original especially these items. I haven't changed much at all. Could be a 73-75 model year setup not sure.

 

[gmachinz]

Yeah its a stock thing...the 73/74 trucks had horrid electrical layouts imo.

Double check you have a GOOD blower motor case ground to the firewall-when that high speed kicks on its a helluva jolt to the electrical system and oftentimes that grounded wire just doesnt “bite” good enough when the relay demands it.