GFI's can be a PIA when they trip for apparently no reason...but there IS a reason and none of them will get me to avoid their use. I'd rather understand and fix the problem than risk becoming part of the electrical circuit!

 

Some of the GFI themselves are junk is part of the problem too.

Then they say there's no such thing as an electric motor "nuisance trip". Maybe. Block heaters are known to cause trouble. Are they all defective too? I kinda doubt that. And I'd hate to have a freezer full of spoiled food or a sump pump fail at a crucial time because of stupid stuff like that. We got along fine without them before? Don't use a hair dryer or the toaster in the bathtub, you'll be fine.

 

LOL, couldn't agree with you more, I removed all my GFI's around the house, its just another weak link........waiting to ruin your day.

 

If you have the time/skill set, take apart the amphenol and look at the connections closely. Poor craftsmanship, moisture (as mentioned already), minor corrosion all factors to be considered. 14.7 ohms is the resistance of the heater element and appears to be sound. Once the inspection is complete and any corrections made then apply the dielectric grease to mitigate future issues.
I had to do this annually with my old 7.3L. NOT using a GFCI though caused the plug to melt once, breaker never did trip and potential for a fire was there.
Went to Marina shop bought another connector and stayed on top of basic preventive care.
There is a reason the NFPA standard for GFCI's are mandated in residential areas. I would never advocate removal or elimination of one, rather look for quality unit from an electrical shop vice cheap big box one. Of course even then YMMV....

 

What Chinookman said!

 

Thanks for the info, could you help me on identifying what the amphenol is?

 

Amphenol connector, fancy name for a plug...lol.......

I used one like this:
https://www.westmarine.com/buy/marin...3?recordNum=20

I went to our local boat repair shop told him I wanted a 120vac charger plug that can be surface mounted. Twice....lol....

Using VOM on Ohm function place one probe on one of the prongs and the other to vehicle ground.
if both of them read zero then there may be foreign material causing a tracking from one of the pins to ground.
That would indicate water tracking, corrosion or maybe a conductor strand touching a ground area......

This is quicker then removing plug and taking it apart. but at times it may take both methods to discover root cause. Based on personal experience finding melted plug because it pulled enough current to melt plug but not enough to trip breaker really got my attention. well scared the crap out of me, seeing how a fire was not far away from this....
A sound electrical circuit 'normally' will not trip a GFCI. However, products with sensitive internal electronics may cause nuisance trips.

If I can be of any further help I'll do my best, hope this helps out a bit.
let us know how it goes......
those root cause analysis results helps us all out.....ah yeah you knew that....

on edit...I re-read you post again........is the plug a solid molded one piece unit or can it be taken apart?
Here are a few more ideas IF it is a one piece molded plug coming straight from the block heater. Should it have enough slack I would consider cutting that male end off and taking ohm measurements again at end of the conductors. Since it is a 120vac heater unit both ends should be isolated from engine/vehicle ground.
If both conductors read an open/infinity on the meter then the unit is isolate from ground and should be a good heater. if one end reads zero to ground or partial resistance then the internal heater element is grounding to block and tripping breaker.
Replace heater element.
Alrighty.....let's see what happens now....!

 

So I found myself at a Ford dealership today and I talked to a service guy who said he works on Super Duty trucks. He told me there is no amphenol connector. Although I don't trust him. He said it was a direct wire into the heating element and it was grounded directly into the frame.

Then I called another dealership and asked them and he told me to look for moisture around the plug (there was none) he told me to try a different extension cord and it still tripped the GFI (this is the same extension cord connected to the same GFI that I sometimes run my Travel Trailer from...A/C unit, fridge, etc with no problems). I have to fly to Minnesota next week...I'm just going to drop the truck off and let them deal with it.

I will report back here what they find.

Thanks guys!

 

by all means...!!!
BTW....since the more we read, there's always a chance we may find a tidbit that makes it all click....

so here is a link from another forum....have not visited in a while buuuuut thought it may help...
if this is not allowed I apologized for not reading the fine print and just delete....

Block heater fuse??? - Diesel Forum - TheDieselStop.com

on edit something did cross my mind.....that needed clarification ..... the use of a GFCI breaker is the correct power source for this application not the GFCI outlet....so this above post did knock a cobweb off the old gray matter.....which for us guys/gals with our shops should have at least one GFCI breaker feed.

 

NEVER NEVER NEVER apply any type of grease to the electrical connections. Connections must be clean and bone dry. This is per Zerostart, and they've been in the block heater business for 100 years.

 

partially agree....
thanks for clarifying this.
1- IF the OEM plug is still in service then no dielectric grease is to be used on the male prong of the plug.
2- If a Marinco type of plug is usd then yes. Use the dielectric grease on the electrical connections on the back of the plug to mitigate corrosion from the elements. The male portion that the extension plugs into then correct, no grease.

Hope that helps ...

 

I have a brand new 2017 f150 and as soon as I plugged it in it blew the GFCI. This is the same plug that I used last winter with my wifes car and my diesel plugged into with no probs. The dealer says all is good so I bought a new cord and same thing again. Next I replace the GFCI plug and still no success. Any thoughts?

 

Moisture, mostly. Nobody is advocating removal, or at least I'm not. They aren't practical or even required for certain things - inaccessible outlets, fire alarms, burgler alarms etc. Long extension cord runs by themselves may cause nuisance trips, apparently. There's no shock hazard in this particular instance, at least not as commonly understood.

 

It's the GFCI, replace it. They wear out, very common issue electricians see.

 

I'm having this issue as well. I took it to the dealer and they said the cord should ohm out at 5 ohms, and that mine was 8. So they ordered a new cord. It's on backorder. I am not sure if the body damage I just did due to heavy load on a gooseneck, ice, and hill will be fixed by the time the cable comes in or not. (jackknife crunch)

I'll let you know what happens when the cable is replaced.