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Grsousa · 05-04-2023, 02:59 PM

My 99 Pinnacle is built on an F53 chassis. Since buying it 2 years ago, the blower has never worked, so while I had the passenger seat out, I decided to investigate.

With the seat out, it wasn't too much trouble to pull the blower motor. On the bench, the motor turned fine with 12 volts, but the cage did need some straightening to turn true. I also discovered the fuse for the blower circuit was blown (the big one that sits in the panel dead center in front of the radiator), so I replaced it.

Put it all back together, and it ran fine (no AC yet, but at least I had heat and defrost). However, the next time I tried running the fan, the circuit was once again dead, due to the same fuse being blown.

If I had to guess, I'd say the fuse went before I tried the fan, but I can't be sure. If so, the fault would be somewhere between the power and the switch, right? Something that would burn the fuse while the blower was not running.

So, what are the likely culprits here? The power takes a rather circuitous route from the battery to the blower, so I'm hoping to map that out, and focus in on the likely points of failure. If anyone has had a similar problem, I'd love to hear what you learned.

TandW · 05-05-2023, 06:23 AM

With blower switch off test for a short to ground with the fuse out, at the fuse socket. If no short, find and pull the blower resistor. Test again for a short, placing the blower speed switch in the various positions. If no short, put resistor back in and disconnect leads going to motor. Test for short.
Good luck!

Grsousa · 05-05-2023, 12:14 PM

Quote:

Originally Posted by TandW

With blower switch off test for a short to ground with the fuse out, at the fuse socket. If no short, find and pull the blower resistor. Test again for a short, placing the blower speed switch in the various positions. If no short, put resistor back in and disconnect leads going to motor. Test for short.
Good luck!

This is exactly the kind of info I was hoping for, thank you.

GeorgeandTheBear · 05-06-2023, 08:53 AM

I had similar symptoms. Sometimes the blower would run, until eventually it just wouldn't run at all, but no blown fuse. Once, while trying to troubleshoot, it started running while we were trying to remove the heat/ac controls. I decided to explore behind the dash, looking for a bad connection or some other issue with the controls. The first thing I removed in an attempt to access the area behind the dash, was the cover above the instrument cluster. Lo and behold, directly behind the cluster was a grounding buss bar. The nut on one of the terminals was unscrewed and just about to fall off. Tightened all those connections and the blower works perfectly now. A blind hog found an acorn in this instance.

153stars · 05-07-2023, 05:58 AM

A dc ammeter will let you test the draw of the blower. I haven't seen too many 12 volt DC motors short in the windings or commutator but it's not impossible. Bench testing will work to see if a motor spins. But to load a fan ,it has to be moving air and you can't really do that with a squirrel cage and not in the housing. The more air it will move the higher the draw. A short in the wiring would still blow the fuse with the motor unplugged but maybe only happens bouncing down the road.
Swapping the motor might save a lot of aggravation.

Grsousa · 05-21-2023, 01:44 PM

Thanks again for the helpful replies.

Testing was a bit puzzling, as the fault was intermittent.

I ended up pulling the instrument cluster for better access. The blower motor feed from the fuse panel emerges from the Ford wiring harness just to the left of the steering column, and from there, the coach builder wiring takes the power across the steering column to the fan switch on the dash.

It turns out the space behind my dash was an unhealthy mix of unwrapped wire and angle iron. The wire for the blower (along with a couple of other wires) ended up between the angle stock and the dashboard OSB. Over the years, the abrasion worked through the insulation, resulting in an intermittent fault.

I fixed the wiring, wrapped everything in split loom, and covered the edges of the angle iron, just to be thorough. Now it's time to address the AC system.