I swear I was always able to plug into a GFCI-protected outlet before! Was I dreaming (for the last 5 yrs!).

Now, it trips the GFI as soon as I plug in. The last couple places I've tried (campgrounds) had fairly new outlets, have they changed, maybe more 'sensitive'?

Is my block heater broken? It appears to work on non-GFCI outlets, but may not be getting as warm as it used to...

I like to plug in 'for free' at camp so I can crank'er up and drive off, minimizing annoying fellow campers at 5am by not having to warm-up abit before driving off. Its also quiter on start-up after plug-in. Ok, the truth is I am a wimp and don't wanna wait a couple miles 'till engine is warm fot HEAT.

Can you plug your factory block heater into a GFCI-protected outlet?

 

I always plug my heater into a GFCI

 

Mine plugs into a GFCI. However, I did have a weak GFCI that would constantly trip with just about anything that I plugged in. I replaced it with a better one and problem solved.

However, a year later my block heater started tripping the GFCI again. Plugged it into a non-GFCI and it tripped the breaker. Tested the resistance and found the plug was bad on the block heater, so I chopped it off and installed a Marinco plug in the bumper of my truck. Works like a charm now, and no plug hanging out of the grill.

If you are tripping GFCI's in more than one place, then it's your truck, not the GFCI. It's easy for the plug to go bad. Just check the resistance, should be something like 12 or 14 ohm's. When mine was bad it was almost 25 ohm's resistance.

 

If the GFCI is tripping, its probably due to a short in the heater. These outlets sense the amperage going in on the hot and out on the neutral. If theres more then 4-6 mA of difference, it trips. Grab your ohm meter and check from hot to neutral, hot to ground, and neutral to ground. If you get a reading on either wire to ground, you might have a bad plug. Cut the plug off and check the wires again. If you get a good reading, put a new plug on. If they're still off, you might have a bad heater or a loose connection on the truck. The block heater cord plugs in above the oil filter. Its the bright orange cord.

 

And look for wear/tear that looks something like this: