The heater blower in my F350 continues to run after the switch is turned off. I checked the relay and it is working properly. Does someone have a wiring diagram showing the control circuit for the blower?

Does anyone know if the heater switch controls power to the relay coil or if the switch grounds the coil to pick up the relay?

 

If you unplug the relay does it shut off?

 

Just discovered a similar issue on my '02 F350, but with a twist. The reverse lights are always on.

My daughter came hole to tell me my reverse lights were on and when I opened the door to see WTH, the heater fan was also blowing. I also detected a slight electrical smell.

Battery is disconnected for the night but some pointers to a potential diagnosis/fix would be appreciated.

 

It goes off if you unplug the relay. The problem is in the control circuit.

Skiddz, If I figure out something I will post it on this thread. I don't have a high enough post count to send you a PM. I didn't notice my backup lights, but the relay for the dome light was buzzing and the dome light was dim.

 

Skiddz

I am being told by a service writer at a Ford Dealership that it is probably the GEM module.

My windshield was replaced and leaks. He said this is common. I don't know.

I found them on EBAY for around $100.

 

Much appreciated

I'm the original owner of the truck and the windshield has never been replaced. In a quick look earlier this morning, I didn't see any evidence of a leak.

I hate just shotgunning parts at the problem. That gets expensive and time consuming pretty fast.

 

I don't think in 99 there is any connection between the gem and blower motor etc..I have the elec drawings and have never seen any...It may have had a high class heater option but its not in the drawings. Later models do something with the gem..

 

I had the windshield replaced. There was a void in the urethane at the upper corner on the drivers side. Water ran down the A pillar and dripped on the GEM and Fuse Block.

The electroncis dried out (finally) and now everything works. I have receipts from the previous owner where he had the GEM and the Fuse Block both replaced in March of 2013.

Hope this helps someone in the future.

 

So it turns out my truck doesn't have a GEM. Took it to the shop on Monday and had everyone scratching their heads. By Tuesday morning, the problem had disappeared and as of about 5pm last night, is still gone.

Shop ran a hose all over the windshield and looked for leaks. None were found and no evidence of any previous leaks was discovered.

The only issue is the Fuse at F2.34 (10A) popped while it was at the shop. I had just replaced it a week and a half ago when I was troubleshooting my cruise control issue. Wondering if something in the steering column is shorted since that fuse evidently kills the Park lockout and the cruise.

I hate electrical problems......

 

Ditto the leak in the windshield for mine. If it rained last night and your blower is running just go to a windshield shop and tell them to re seal it.