Testing Block Heater

[benderado]

I know there are a ton of threads on cold start troubles and block heaters, but I can't seem to find one that matches whats happening with me.

Both my roommate and I drive diesels and we both plug 'em in when it gets cold. All of last winter we never had a single problem.

However, since it has gotten cold here, the breaker connected to the GFI outlet outside has been blowing.

This morning, my roommate did some "testing", by only plugging in my truck and sure enough, it tripped the breaker again. I use a 25' extension cord and my plug is in the opening of my bumper.

I've borrowed a multimeter from work and did some basic testing (due to my limited knowledge of household electricity). The extension cord is good, .2 ohms on both sides.

I also ran resistance on the block heater, it started at about 20 ohms and climbed to about 150 ohms. I have no idea if this is good or bad.

What else should I test? Could the block heater be bad? How hard are they to change?

[benderado]

Someone has had to of tested their block heater before!!!

[toads250]

Block heaters draw about 1000 watts, I had a problem when I plugged mine in, in the garage,when the air compresser would kick on the gfi would pop... no frezzer, air compr. and no block heater so ahd a electrcian friend wire a plugin 50amp fuse right from my main panel and now no problems.

[cndrm]

To me, it sounds like your block heater is working fine. The resistance creates heat, therefore heating your block/ coolant. It's not uncommon to have electronices of this type, increase their resistance as the heat goes up.

I think that it's odd that you had no problems last winter, but you do this winter. What gauge extension cord are you using? I personally wouldn't use anything smaller than a 12 gauge, and preferably using a 10 gauge, but that's me.

There could be quite a few things causing this problem. It's tough to say. Do you know what else is on the circuit that you're plugging your truck into? As Toads250 said, he also had an air compressor, freezer on the same circuit he was plugging his truck into. It could be something as minor as an appliance getting a little old, and drawing more current than before. Then you plug in your truck, and pop goes the breaker.

mike

[ridiculously_necessary]

anything new go to that breaker? liek anyhtign installed over the summer?

also, i hear breakers can get old and flip when they shouldnt. ive been told thats a good sign they need to be maintenanced. i also understand the breaker switch should be stiff and not soft when flipping.

[benderado]

Well, I had it plugged in all night last night with no breaker pop. So my only conclusion is that having both trucks plugged into the same outlet is drawing too much and poping it.

I believe it is a 40 amp breaker and is soley for the outlet outside.

When my roommate gets back we'll see if it pops again and if it does we'll go from there.

[Big Bird]

If the block heater is indeed a 1000 watt heater, then it draws approximately 9 amps at 110 volts. A 40 amp breaker should be ok for both trucks if both draw less than 20 amps.

One test you could do is to ohm between the plug and the frame on the truck. It may be possible to have a short develop if the cable wears on the body or frame. This problem may be intermittent, and probably would be a good idea to visually inspect the cable to check for wear.

[cndrm]

^^ good post.

mike