This moring it was cold (10*) and when I plugged in my engine block heater it kept popping the ground fault on the outlet. I have been using the same outlet all winter with no problems although this is about the coldest it has been so far. Then I tried to plug it in into an outlet inside the house and it is working and stayed on. Does anybody know what is going on here? Is it a bad ground fault? Does the colder temp make it draw more power? Is it a bad idea to have it plugged in to an inside outlet? Any insight would be appreciated.

-Dan

 

The outlet could be bad. Did you plug it in to another GFI outlet? If it's working fine on an indoor outlet and it hasn't tripped the breaker, it doesn't sound like there is a short, but maybe a large initial load. When you used the garage GFI outlet, did you leave it plugged in, reset it, and it still tripped? Or was it just tripping when you plugged the cord into the truck?

 

The GFCI outlet is fine, GFCI works by sensing a difference in resistance between the neutral wire and ground wire, since your truck is not grounded directly to your house wiring (as opposed to a light fixture, it grounds through the extension cord) it senses enough of a difference and trips. Just plug into a non GFCI o/l and it will be fine. Sometimes you can plug it in first and then reset as mentioned above, but can still trip later in the A.M.

 

I would suggest plugging it in to another GFI and see what happens. It only takes a short or leakage current as small as 4 or 5 milliamps to trip a GFCI but is not enough to trip a circuit breaker on a normal circuit. The only problem with this is if the current gfci that trips is not in fact bad and you do have a faulty block heater or cord that you pose a risk of someone getting electrocuted. At the current time it could only be a 5milliamp short but if it gets worse and does not have gfi protection then you have the potential for anyone who gets in your truck to receive and electric shock or possibly causing an electrical fire. I have been an electrician for 7 years and have come across this before, I had a customer call me last year because every time he grabbed the handle of his 1994 f250 while having it plugged in he got the shock of a life time ( Nice metal door handle while standing in the snow) He said it kept tripping the GFCI on the outside of his house so he plugged it in on the porch that had no ground fault protection. It turned out to be that there was a small cut in the block heater where it rubbed on the frame.

 

A GFCI senses the difference of current (AMPS) between the Hot wire and the neutral. Think of it as it watches how much power is leaving the outlet and how much is coming back, if that number differs by as little as 4-5 milliamps then the GFCI trips. The block heater is grounded back to the house wiring via the three prong plug which carries a ground from the house to the block heater which intern grounds the truck. The length of the cord will not trip the GFCI unless it is a bad cord nor will the initial current it takes plugging in the block heater for the first time because what current is being used by the heater is being returned to the GFCI unless there is a short allowing the current to return elsewhere like the ground, then the GFCI trips to prevent harm. As I stated in the last post, try a different GFCI to rule out that the GFCI is bad, then look at the cord, block heater and block heater cord. It would be dangerous to plug the truck it to a normal outlet knowing it has a ground fault problem.

 

wow thanks for all the info. I have a new variable to this, after the heater was plugged in to the non GFI outlet for about an hour I unplugged it and plugged it back into the GFI outlet and everything is working fine and it didn't trip the GFI.

 

He's absolutely right, after reading my post......I didn't have enough java yet! Check your wiring harness, extension cord, etc. There are faulty GFCI out there but have seen very few, they won't trip unless there is something wrong or it's a bad o/l. I have plugged my '03 into a non-GFCI many times either because there wasn't a GFCI available or it kept blowing due to the prongs being wet or ? reason, just be careful when plugging in/out, especially when standing on wet earth.

 

Using a non gfci is fine i always prefer to plug it in to a gfci if avaiable just for saftey and an extra piece of mind, just did not want anyone to think that plugging it in to a non gfci was a fix for triping a gfci. But it dose take very little for them to trip, just having water on the prongs of the plug can short enought current to ground to cause it to trip. Damed if you do; damed if you dont. Everyone have a good Holiday.

 

Mine did the same thing last year, i pulled the end off the plug and the wires were all corroded so i replaced the cord, that fixed the problem

 

Sounds like your heater was able to build up a little internal condensation which gave you a high resistance ground and running it on a non GFCI let the moisture cook out. You may have just had the right combination of cold and moisture commonly referred to as Dewpoint. Good luck but you are probably OK. If it continues to be a nuisance you may have to change out the heater or at the least, trace your cord for any cracks in the insulation.

 

I've come across quite a few bad GFI outlets. They're almost as common as bad breakers. When you're dealing with something that is designed to fault quickly with the smallest amount of variance it doesn't take much to have a GFI or breaker go bad.

 

I completely agree and GFI breakers/outlets seem to get weak over time and tend to want to pop with larger loads such as a block heater.

 

The truck is an 07 so corrosion really should not be a problem. Yesterday after I drove it and plugged it back in it tripped the GFI again. Earlier in the day I had it plugged in for 4 hours, would that be enough time to cook the water out?

 

check the heater cord like mentioned above and pull the actual plug apart off the heater just to make sure there is no corrosion or it wasn't assembled wrong from the factory where there is a wire strand that strayed to where it shouldn't be. Do you have a diff extention chord? try a diff one tonight just to make sure its not a bad chord. another idea, how thick of an extention cord are youj using? try to not use the small little cheap ones for three bucks at walmart. your truck needs to make a certain electrical draw and if your cord cant supply that it will make the gfi trip. try a thicker cord. Good luck!

 

How old is the drop cord you are using? And how old is the GFI outlet?