da-bees - appreciate the input, but it's not my intention to take the GFI circuit out of the loop. My truck is not in a garage, but I like the extra barrier of security.
Are you by chance saying that the outlets could be bad - due to the resistive load?

 

I would try it on another circuit. You say you have Christmas lights on the same circuit? If the heater is pulling 9 amps are you using the other 6 amps on lights? Are you sure your not blowing a load?

 

Yeah, its just a few Christmas Lights, even with all that other stuff plugged in, it still trips. I just tried another outlet/circuit and it didn't trip. So I guess I have to get another GFI - frustrating!

Thanks for the input guys!

 

I'll second putting the truck on it's own circuit and see if it's still causing you trouble.That's about normal, or at least from what I can find.

 

Actualy I included some of the info because it might help others reading this thread and certainly doesn't obscure your case.
I am not only saying the outlet could be bad,any of the items mentioned might be bad.
At the risk of appearing rude,you are figurativly and literly playing with fire eventhough the truck is outdoors. From the plug back to the breaker box is likly inside your house.
If you want to continue tracking it down rather than call a friend to help,start with what Ed suggested about different outlet that is on a different breaker. After that let us know what happened and we can move to next step.

 

Try changing the extension cord out. It may be saturated with moisture, like mine was. The gfci's are sensitive outside. 15 ohms divided by 120 volt= 8 amps, so the block heater element is most likley good.

 

Man i have tried so many different things today, still cant really hit the nail on the head so to speak. I have changed out all the GFI outlets, that didnt fix it. I tried several different extension cords, still trips. It only trips when i plug the block heater is plugged in. If i plug the heater into another outlet in the house, it's fine. With the block heater i draw just under 8 amps, with all my outdoor lighting and Christmas lights it only draws like another half amp.
I even tried another new heater cord with another extension cord and it still trips, which eliminates the heater cord being faulty. I seem to have a fault on the gfi line some where just cant figure it out...... I gave up for the day, waste of a day, atleast the heater doesnt need to be replaced.
Thank you for stating the 8 amps though, that makes me feel even more assured!

 

My factory plug went bad, i cut the ground off first. With gfci protection the ground wire is not necessary. I did eventually replace the plug with a heavy duty 15 amp type. I don't remember if you checked the hot to ground & hot to neutral resistance?

 

I didn't have anything to ground, at least on the truck.
A friend, who is an electrician, also suggested something similar, but actually getting one of those plugs that gets rid of the ground pin.
I did verify it's not the heater plug, not the cords. What I can't be 100% sure of is where I am getting the ground short, or if that is in fact the problem. My understanding is that GFI's are very sensitive and it could even be just a small slit in the wire insulation that could be causing the problem - due to a electrical "leak", as it was put. It could also be a very minimal amount of moisture that makes it trip....

 

Just get it off the GFI they suck
A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second.

I have had nothing but problems with my GFI outlets the slightest bit of moisture or anything and it trips
If mine was plugged into a GFI and it rains or even snow I can count on a cold truck
and the more the GFI trips the more sensitive it gets so after awhile if you look at it wrong BOOM it trips

 

What was your fix?? Did you take it off the GFI?

 

2" hole saw is what I used.... 1 7/8 is an odd size and what they recommend (Marinco) but the 2" did just fine. I use a Christmas light timer (outdoor type) on a fused power strip , plugged into a GFI and never tripped any of it

 

I have had various things not work correctly on a GFI that function fine when plugged in to other outlets... we have this automatic litter box for my girlfriends stupid cats and it trips the GFI EVERY DAMN TIME. We had to run an extension cord to plug it into a different outlet.

Not sure if there is a resistance differential or if the motor in it is a large load or what. I mean we have plugged the big vacuum into that outlet and never had it trip.

 

They save lives by shutting off if there is a 5ma current imbalance between the hot & neutral. The new ones are less sensitive to false tripping, when they fail they trip off. You have other underlying issues, I wouldn't remove a gfci for a outside outlet. i installed 25-30 of them for a garage hauler, and they don't have any problems with them. Could the insulation from the original cord rubbed off?

 

Bought a $4 Digital Timer from Harbor Freight... works great!

Brook
'04 F250