Blower fan stopped working- need wiring help

Damon

Pro Stocker
Feb 7, 2005
1,655
1
38
Philly Area
Naturally, on the hottest day of the year today, by blower fan stopped working. Nothing on any setting.

Got it home and tested the motor itself by running a jumper from the batt to the power connector- it works like a champ (it should, I just replaced it a few years ago). Checked all the fuses... nothing popped. Everything else electrical in the car works fine, as it always has.

So it's something in the wiring between the switch, relay, resistor pack.... I don't know where to start. Anyone got a wiring diagram? Thanks in advance.
 

Damon

Pro Stocker
Thread starter
Feb 7, 2005
1,655
1
38
Philly Area
How did I never know those diagrams were on this site?

Thanks. I might have a question or two before I dig in.

Like... how does the High Speed Blower Relay work? I'm not that great understanding all the little squiggles on a schematic. That one has me scratching my head. Especially the curly-que on the right side of it. What is that?
 

Damon

Pro Stocker
Thread starter
Feb 7, 2005
1,655
1
38
Philly Area
Wait, I get it. It's the relay coil. When you select HI on the fan speed it activates that circuit, closes the relay and connects the batt-hot big red wire directly to the big purple wire that powers the blower. All other fan speed settings it taking juice from one of the circuits on the resistor pack to power the blower. Got it, got it.
 

t01blaze

Amateur Racer
Dec 14, 2011
247
0
0
South New Jersey
Yes. It appears to be a SPDT relay. Blue and purple are connected when the relay coil is not energized. When you supply power (orange wire) and ground to the coil, the relay breaks the circuit between blue and purple and now instead connects the red and purple wires.
 

Damon

Pro Stocker
Thread starter
Feb 7, 2005
1,655
1
38
Philly Area
And the winner IS!! .... bad blower motor ground.

Just crudded up enough it would jump the rust if I ran a wire straight from the batt to power the motor. But through the fan wiring it lost JUST enough it wouldn't do it (at least not consistently- occasionally it could kick on out of the blue). Cleaned up the ground, problem all fixed. I'm glad it wasn't a switch or a wiring problem. That would have been a lot harder to figure out and I imagine finding a new/original fan speed switch might not have been easy.

Reminder to all that it's easy to get the blinders on looking at the (much more complicated) power feed side of things, when sometimes it's just a simple ground that's the problem.
 

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