Help with Heater Wiring

[zsmith]

Hey Everyone,

How many volts does it take to get the heater motor going? I rebuilt and installed my heater and it started smoking (yikes). Any idea what I did wrong? Now I when I have a voltage meter on it and am consistently getting around 7 volts when off, does the voltage jump up when it is running? I am assuming it was a ground but I was hoping to test the system with the car off but it seems like that isn't possible. Sorry new to electricity. I know the motor works because when I put it directly on the battery it fires right up. Brand new heater switch.

Thanks for the help.
Zach

[DirtDonk]

Re: Help with Heater Wiring

Maybe the new switch has failed? Or maybe something with the wires or the resistor perhaps.
You should not get any voltage when the switch is off. I've never measured voltage on LOW, but that 7 could in fact be normal. Seems like it should be more like 9 or 10 though.
Only on high would you be getting the full 12v, or whatever your system is producing and whatever is making it through the switch. In other words, with no voltage drop and the engine running, you should see 14.5 at the switch.

Is all the wiring new on the truck? If not, it's not unusual to see voltage drops from the battery to the heater motor due to rusty contacts, old wires, and faulty switches. I know you said the switch is new in your case, but it's still worth testing.
I don't remember ever hearing of someone getting a bad switch from us, but it does happen. Not sure where you got yours, but the general quality of electrical auto parts has plummeted in the last 20 years or so.

Did you wire it so that the HIGH speed comes on first, then the LOW? That's how Ford did it, so was wondering.
And what was smoking exactly? Could you see?

Good luck.

Paul

[zsmith]

Re: Help with Heater Wiring

The motor started smoking. Good call on the measuring of the wires I'll try the voltage on those. I think need to try it running and see if that changes things. It is the original wiring but it isn't so far gone that I am having problems. The original switch broke as I was removing it. I did notice it was hard to get a good ground. I am thinking my battery is a little low as well. Any idea why the motor would smoke? The original motor now works though when I connect it to the battery directly. Thanks for the help. I'll try measuring the voltage after the switches (I just by passed the switch yesterday to make sure I was getting something. Thanks for the help!

Zach

[DirtDonk]

Re: Help with Heater Wiring

I only pretend to understand all the little idiosyncrasies of electrical and electric motors. So I don't know if low voltage combined with trying to start a motor spinning pulls more amps than the same thing with full voltage. If so, the higher amperage draw could have overheated things temporarily. But that's just a wild-assed guess to throw out for the experts in electric theory.
Could have been dust or something inside the motor, but it sounds like a new motor, correct? If so, smoking is not normal even on the first startup to my knowledge. At least I've never experienced it when all was as it should be.

The power in to the switch (Brownish wire I think?) would be a good place to start measuring for voltage. Make sure you're getting at least within a half a volt of what the battery is. But if the battery is even remotely low, I would charge it fully before really getting into measuring things in ernest. Just going to give you odd readings.
But no matter what the battery voltage is, you should note it so you have your basic point of reference. If you see a full volt or more drop in your readings under the dash, you're just working against the current (pun intended!) and your old wiring. Corroded connections are a pain. And corroded fuse contacts are the bane of Bronco owners existence!

So that would be another good "first place to start" in this quest. Pull and check all fuses. The big 30 amp one (I think?) is the heater. It's marked on most EB panels though, so you should be able to determine which one it is. Get it out, check it and clean the contacts the best you can to make sure all the power is getting where it's supposed to.

Paul

[zsmith]

Re: Help with Heater Wiring

Paul,

Thanks for all the help. Work ramped up so I have not been able to get back to the garage. I just replaced the fuse this weekend and it had been in fact blown. Even with the new fuse I couldn't get to run. I'll charge the battery this weekend and try again. My hope is the battery just needs more juice. I'll also use the voltage tester on a couple new connections.

Thanks again!
Zach

[zsmith]

Re: Help with Heater Wiring

Figured it out! The original reason for the over heat was that the squirrel cage was bound up on the box housing which caused it to over heat. Then which blew a fuse some how. Then the replacement fuses needed to have the contacts cleaned on the fuse box in order to get a good connection causing the inconsistent voltage. Fixed and fixed. Boy did I learn a lot with this one! Thanks for the help!

[DirtDonk]

Re: Help with Heater Wiring

Wow, great you got it working. Lots of steps to get down that road though!
Good you just kept at it and fixed all the little things that were adding up.
Congrats.

Paul