Heater wiring

[TrueNorthist]

The heater abruptly stopped working on my gen 2 (91, 3 litre auto). The fuses are all good but the blower simply does not power up regardless of settings. I see the A/C is tied into the same wiring. The A/C compressor is failing so I have not bothered to charge up the r12 and wonder if that may be the problem? Anybody know of a quick-fix for this? I do not intend to repair the A/C, at least if I can avoid it.

Cheers!

 

[nevada]

pull the plug from the blower motor, and verify 12v, or lack of.

I have seen blower motors just die suddenly.

 

[fourwd1]

You could also apply 12V to the blower to see if it works.

 

[TrueNorthist]

I get power across the fuse (the 20amp fuse behind the glove-box) but none to the connector, and if I apply 12v direct to the connector the blower flashes up fine. The juice just isn't getting to the blower which is what leads me to wonder if the A/C has anything to do with it. Is there a low freon pressure cut-out of some kind? I have noticed that if the a/c button is pressed the light no longer illuminates. BTW, the rear heater blower works fine.

 

[nevada]

its unlikely that all the speeds died, but you could check the heater speed relay, it should be mounted IN the heater box somewhere.
im not exactly sure where its located on that rig, but look around under the glove box, near the blower motor. you should see a plug going into the heater box. 4-5 wires maybe.

there is a low Freon switch, but it should be unrelated to the heater controls.

 

[TrueNorthist]

The blower does not work on any speed which makes such a failure unlikely, but I can't say impossible so I'll check. I was looking at the schematic and it shows several grounds are shared with the a/c... But procedure matters here. I'll report back shortly.

Thanks for stickin with it.

edit: there is also the heater relay and blower resistor that I will poke at.

 

[TrueNorthist]

Swapping the blower relays did the trick, but now the rear blower doesn't work. I'll snag another relay to keep the wife and former sweetheart happy.

BTW, the lunch-box worked great. I get minimal increased under-steer but can deal with it easily. 4x3 sure ain't bad.

Cheers buddy! I owe you a jug of your choice. :cheers:

 

[nevada]

awesome man, im glad you got it fixed, and that it was something simple.

odd that all the speeds went out at once tho. must have been a common wire in there that failed.

 

[TrueNorthist]

There are relays for both blowers right next to each other above the fuses which meant I could simply swap them. The wiring was fine, at least this time. A bit of rust oozed out of the bad unit so the guts must have corroded badly while in storage. I'll be sure to rig up a desiccator lamp this winter to keep her dry as a chip.