Hi all, I have a 2000 F-350 (7.3) with the original block heater. About 2 years ago I replaced the plug since it stopped working. I haven't tested the ohms on the plug, but I was wondering if it trips the GFI (I tried 2 separate circuits) does this indicate a bad heater or should I try replacing the plug again?

Thanks,
Eric

 

Could be either. check with your ohm meter from the ground pin to the neutral pin (the wide one), it should read infinite. Hot to ground should also be infinite. Check with the cord disconnected from the heater first, if it fails replace the cord or check for wiring error. If it passes hook it back up to the heater and test again. If it fails this time then it's the heater. Any continuity between the element and the grounding pin will trip a gfci.

As far as element resistance (hot to neutral) for a 1KW heater which I believe is what ours are rated you should see around 14.4 ohms.

Note that a wet connection point will also trip a gfci

 

If it trips the GFI, you have 1 of the 3 is at fault. First just plug in the ext cord, if that doesn't trip the breaker than plug just the cord from your truck with the heater unplug at the block. If that doesn't trip the GFI, than more than likely the heater is partially shorted out. Much like the electric element in your house water heater, they will sometimes get a hot spot and split the side of the element and some of the electric current goes somewhere else and that is what causes the GFI to trip. The GFI measures the amount of current out and back, if it senses any difference it trips. HTH's

 

I installed a brand new block heater and GFI... it trips it anyway. I never looked into it, I just use a timer on a normal outlet from the garage.

 

I pulled my heater cord totally out. Cleaned all metal with wire brush. I then checked for even the most minute kinks or marks on the entire cord. Low and behold, I pulled back and cut the insulation at the "kink" and 2 of the 3 wires were bare or close to it!!!! Connected them with wire nuts (cheap I know but it should get me through this winter), electric taped and sealed it all back up. Haven't tripped the circuit yet (knock on wood)... Hopefully this'll help OP out!!!

 

something else to keep in mind:

The way my house is wired all the GFI circuts in the house go to one breaker.One outlet in each of 2 bathrooms, 2 outdoor outlets and 2 in the kitchen. So.....if my wife fires up her hair dryer and hair straightener...it is cold enough for the dogs water bucket thermostat to kick on and my truck is plugged in that poor 20 AMP gfi breaker dosen't have a chance.

Is there anything else plugged in to your GFI that might be overloading it?

 

I have my block heater on GFCI as well, trips once and a while, usually if the connection gets damp/wet.

I'd follow the other advice on the thread as well..may be bare wires!

 

I was just with a guy whose 02 element was toast
He had bought a new cord and element and he is all good!

Spend the $$ and buy both, if your truck is a 1999-2004

 

OK - So should I go with the 1500w unit or stick with the 1000w?

 

Same exact thing here at my house.

 

I'll try pulling the wire out and test it. Do you know a good site to get a new wire?

 

I tested plugging it in to a plug without a GFI. It ran because the motor started with much less effort on a 25 degree morning. I guess it's shorting out the GFI but is still good.

 

They both fit the same and use the same heater plug. Either one will work. The 1500W will heat up the fluid faster and use more energy (cost more) doing so.

Assume you have the 1500W heater. If you are paying $.25/Kwh, then you will be paying about $.375 per hour x the number of hours you have it plugged in.

Assume you have the 1000W heater. If you are paying $.25/Kwh, then you will be paying $.25 per hour x the number of hours you have it plugged in.

How many hours you have it plugged in makes a BIG difference.

 

Mine tripped GFCI and appeared to 'work' - but looked like this:





This fixed it right up!!!



I didn't know there was a 1500watt option. The only disadvantages I can think of is needing a dedicated circuit, larger ext. cord and heavy-duty timer to run it.

Kind of related - here's my Marinco mod:







I 'fixed' the cover popping open problem by installing an injector o-ring on it:

 

I bought a new cord at the IH heavy truck dealer for just under $30. Ford wanted $120, I think. You can buy a replacement heater and cord (both) for $60 from an auto parts store, and just use the cord, if you have no handy IH dealer.

The IH replacement cord is nicely made and has a better end-fitting (screw-down) than the crummy steel clip that Ford used, which cuts into the rubber. I would not risk using wire-nuts on a block heater cord, given the occasional engine fires, etc. that can happen with high-current heater cords plugged into trucks.