Block heater tripping GFCI? - Diesel Forum -
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post #1 of 5 (permalink) Old 12-08-2005, 10:17 PM Thread Starter
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Block heater tripping GFCI?

My first winter in cold weather ... as it got down below freezing, I was using a timer to have the block heater go on a few hours before morning. Its been working fine, cold starts not a problem. Tonight, first real storm with snow and sleet. When the timer kicked on, the GFCI on a connected outlet would trip. Eventually, I traced it to the plug on the truck. As soon as I plugged it in, the GFCI would trip. Is this typical? It has been working well until just tonight.

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post #2 of 5 (permalink) Old 12-08-2005, 10:35 PM
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Re: Block heater tripping GFCI?

Not typical but quite a few will do it. My own truck will not trip a GFCI but my old 6.5 chevy would. There can be a very small leakage to ground, 4 milliamps, that is not dangerous but will trip a ground fault interrupter. If you have a meter check the prongs on the block heater to the truck body. If the resistance to ground is over 100K ohms then all is well.
Parking it outside where even a small amount of moisture gets in the plug will cause it to trip.
Try plugging it straight into the wall without the timer. Some of the timers are as cheaply manufactured as they can be.
Try a different extension cord also.

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post #3 of 5 (permalink) Old 12-09-2005, 05:56 AM
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Re: Block heater tripping GFCI?

Make sure you are using a big enough timer and extension cord, then I would try and keep all connections as dry as possible. I did the Marinco mod and it keeps the connection good and dry and makes it much easier to plug in.

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post #4 of 5 (permalink) Old 12-09-2005, 07:24 AM
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Re: Block heater tripping GFCI?

any rain/snow or damp on the plug will do it on a gfi. they are looking for a short and it dont take much to tell them to trip and cut the current. a fog is all it takes on mine

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post #5 of 5 (permalink) Old 12-09-2005, 07:41 AM
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Re: Block heater tripping GFCI?

My 6.2L Chevy trips the GFI due to a short somewhere.


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