Ford 3500 intake heater amp draw

[City Farmer]

Hi guys. I need to wire up an intake heater on a Ford 3500. It's a factory heater with a fuel line going to it. I put a jumper to it and it lit right up. I swapped out the gas engine for a diesel. I was thinking of using the hot coil wire with a 5-10amp fuse to a push button starter switch. I'm a little worried about the current draw, Is it to many Amps?

Andy

 

[sea2summit]

You mean 350?

 

[City Farmer]

You mean 350?

No, it's a 1970's industrial tractor/backhoe.

 

[sea2summit]

No, it's a 1970's industrial tractor/backhoe.

Oops, talking about tractors in a tractor forum. I got it now.

 

[Dave M7040]

Hi guys. I need to wire up an intake heater on a Ford 3500. It's a factory heater with a fuel line going to it. I put a jumper to it and it lit right up. I swapped out the gas engine for a diesel. I was thinking of using the hot coil wire with a 5-10amp fuse to a push button starter switch. I'm a little worried about the current draw, Is it to many Amps?

Andy

I think what you have is properly called a THERMOSTART.
I would expect it to draw about 50 amps but only for a short time so no problem for the battery.
You just need to make certain your wiring and switches are heavy duty enough.
Here is a description from another 3000 owner which I found.
I have a '65 3000. The thermostart device is an electrical heater, a temperature sensitive valve, and a fuel supply via a small tube from the fuel tank.

The way it works is that you rotate the key switch from OFF to ON (lights on) to Thermostart, hold for 30 seconds or more depending on temperature, and then over to Start which not only runs the starter, but keeps the Thermostart element heating.

The Thermostart/Start positions put 12v on the hot wire in the Thermostart device (located at the inlet of the engine's intake manifold) which heats up a temperature sensitive valve which opens when hot.

Opening this valve dribbles diesel onto a glowing wire (in the thermostart) which ignites the diesel and you essentially drop glowing globs of diesel into the intake manifold as you are cranking the engine. Sounds crazy, but I spent a lot of time understanding it (fixing mine cause I had no instructions) and it works.

Dave M7040

 

[City Farmer]

Thanks DaveM7040.
I NEVER would've guessed it would take that much juice to run that little heater. I'll pull power straight from the battery.

 

[RickB]

Not gonna draw anywhere near 50 amps which would require an 8 ga. Wire. The OEM wire size for the thermostat is no larger than 12 ga. The element is not the heat source, burning fuel is. If that little coil draws 15 amps I'd be surprised.

I swapped a diesel into my gas 3 cylinder 4000 several years ago. I did use the coil primary wire to power the thermostart. Works just fine.

 

[Soundguy]

Agreed, I'd fuse it at 20 to protect the wiring and go.

 

[skyhook]

Have one of those on my JCB, a push button starter switch should handle the amps, although you should have a "relay" to handle the amperage to the thermostart from the switch, a relay of 40 amps should be fine, in cold weather, you can keep it "activated" for a good 20 seconds (this is where your battery will loose some drain ) and keep it activated while you start your machine. A 20 amp fuse should be good, but if you find it blows, just upgrade to a 30. The length of time you use it will determine the fuse size.

 

[City Farmer]

Thanks Rick & Soundguy. I'll go #12 to the switch with a 15amp fuse to start.
Its almost the same swap you did Rick, it's a 3500 diesel going in a 4400 gas.