Block heater question

[Cheaper Jeeper]

Got a weird one guys.

My truck has a block heater installed, but the PO (the truck is from California) cut the plug off the cord. No big deal, just get a new piece of 3 conductor cord with a 3 prong plug, and splice it to the cord that's there, right?

So I did just that. Both cords have a two 14 gauge wires, and a lighter gauge green center conductor. Easy-peasy. Spliced 'em together and plugged it in and ...FIREWORKS! Sucker made a big flash, threw sparks, and tripped the breaker - but not before welding the prongs of the new plug into the socket of the extension cord!

So I managed to get the prongs out of the socket, and everything still looks usable, so I go get my volt/Ohm/amp meter. Now let's call the 2 flat prongs #1 and #2, and the round grounding plug #3. Using the Ohm meter I measure ~ 15 ohms between 1 & 2, and the same between 2 & 3, and the same between 1 & 3.

So I do a little math.

Volts/Ohms=Amps, right?
So thats 120 Volts / 15 Ohms = 8 Amps, and the 14 gauge wire is good for up to 13 Amps. So far so good.

Volts x Amps = Watts, right?
So that's 120 Volts x 8 Amps = 960 Watts. So it must be a 1000 Watt (nominal) block heater.

So why the HECK is it tripping breakers and behaving like a dead short? Is there something I'm missing here?

Anybody with a block heater installed got an Ohm meter and would be willing to take measurements between the plug prongs #1 & #2, #2 & #3, and #1 & #3, and post the results here?

 

[h2odrx]

No tester but you pay shipping and I'll send you a used cord?

 

[LCAM-01XA]

Gimme a few minutes to finish my NCIS show, then I'll measure mine up for ya.

 

[k_williams1982]

I had a cord that would keep tripping breakers. I replaced the cord and found out that the heater itself (inside the block) was shorted out. That could explain why the PO had cut the cord.

 

[LCAM-01XA]

Jeeper, I posted replied to you at FTE, but I tried measuring mine last night, and got open circuits between any combination of prongs (1-2, 2-3, & 1-3). Mine is probably dead then.

 

[Cheaper Jeeper]

Well, one responder on FTE said he got similar readings measuring between the flat prongs 1-2, but open circuit measuring from either flat prong to the round grounding prong (1-3 or 2-3)

Wonder what would happen if I just clip the wire to the #3 center ground plug?

 

[4play]

sounds like a short to ground either in cord or heater element. probably faulty element, just take same measurements at element with unplugged. then while unplugged go ahead and re-measure cord.

 

[vegas39]

If you are getting a reading from either prong one or two to prong three, then you have a hot going straight to ground, not good.

If you eliminate the ground, you may still blow the breaker and if you dont blow the breaker, you may get one hell of a jolt when you or anyone else touches the truck! Especially when standing on wet ground.

 

[vegas39]

While were on the subject of block heaters, are they o.k. to use? Seems like I read somewhere that they had issues. (engine block problems)

I have an 86 F250. I guess before I plug it in, I will do an ohm test on it.

 

[BROWNIEBOY525]

While were on the subject of block heaters, are they o.k. to use? Seems like I read somewhere that they had issues. (engine block problems)

I have an 86 F250. I guess before I plug it in, I will do an ohm test on it.

i think that was on the 83-84 blocks that were thinner were the heater was it would crack. Yours should be alright to use.

 

[nukinfuts]

So what heaters are best to use? My heater had the same issues.

 

[tractorman86]

anyone know where i can get a heater? original engine had one but new motor doesn't have one.

 

[LCAM-01XA]

Aight, I found out my heater is just fine - problem is my wire to the right flat prong is pinched right near the plug, hence the open circuit reading at the prongs. Now that I know that I measured it again, got 15 or so amps, so heater's good - now just to get another cord and splice them together...

 

[BROWNIEBOY525]

anyone know where i can get a heater? original engine had one but new motor doesn't have one.

you can get them from napa

 

[tractorman86]

right on i dont have any faith in checker to figure something like that out but didn't even think about napa