GFI trips when block heater plugged in?

[markrinker]

Truck #1 and truck #2 both parked in the driveway. Both have OEM block heaters.

Attempted to plug in #1 to same outlet I have used for years. GFI trips.

Plugged in #2 after resetting GFI. No issues.

Both plugs have all three prongs, no visible frayed cords.

WTF?

[MikeChase]

Mark -
I believe the GFI senses current balance between hot & neutral. More current flow out one leg than in the other trips the GFI, as when there is a path to ground. There is probably a short in the
block heater wiring on truck #1. Try checking for continuity between the ground terminal and the other two terminals on the plug, which would indicate a short. You'll likely need to replace the block heater IMO.

[markelectric]

GFI's will trip if the nuetral and ground become connected. A quick way to CHECK is to use a 2 prong adapter. My experience tells me you probably have a failing element. In this case the above check would heat the truck more ways than one. Just dont touch the truck while testing.

[tom.mcinerney]

SSuggest follow above advice to check.
But maybe a little salt spray is conducting externallyy across plug prongs...so if all else seems ok maybe flush w fresh water dry push plug on all way.

[ace58]

The garage at my house also has ground fault protected outlets. I have a 99 van and a 99 Suburban both with 6.5 diesels and block heaters. When the Suburban tripped the circuit, and after all was said, done,and tested, the cord had a short at the actual block heater element terminal. All is well since.

[alaskaflyer]

We do a lot of electrical work in the property projects we own and have discovered that your gfi outlets will weaken over time and cause it to trip. So if the other responses don't seem to work try replacing your old gfi outlet with a new one.

[BuffaloGuy]

GFI's and block heaters are the pits. They are too touchy. Change it out to a regular outlet and just make sure your breaker is in good shape. That's all you need.

[markrinker]

It did turn out to be a block heater going bad. Replaced it and it seems to heat and start better than ever.

Wondering if block heaters can get 'weak' without failing, causing hard starting?