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Q's about Ohms law and block heater

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Q's about Ohms law and block heater

Postby Used2baFordDrvr [OP] » Jan 16 2020, 2:13am

Holy crap, we are stuck in the minus 40* temps of an Alberta prairie deepfreeze. It looks like we'll be in these freezing temperatures for at least another seven days or so. I had to put a new battery in the truck as the old Die Hard did exactly that. I went to plug it in a few days ago and discovered two plug in cords under the hood. When I OHM'd the plugs on the cords I got a reading of "1" on the OEM thermostatic plug telling me that there was no resistance in the cord and it was virtually pooched/useless. The other plug gave me a reading of 17.4 which is in the margins that I would expect for a working block heater so I used it for my plug in. Only problem was that I could not hear the expected sizzling of the element heating the block water. With the new battery installed the truck was turning over better and starting yet I was sure that it should be turning over more easily that it was. Today, at -38* I crawled under the truck and traced the cord that I believed was the good one. It led me to an oil pan heater and NOT the block heater that I had hoped for,

This afternoon I cut off the thermostatic plug on the OEM line and replaced it with a plain plug in male end. I eagerly plugged this in and listened intently for any signs of sizzling and a working block heater. Again, I was denied. I OHM'd my new install at the plug and got a reading of .034K OHM's. If I did the math correctly (.034 X 1000 = 34) it showed 34 OHMS and a working block heater yet I received no indication that it was working. My understanding is that I should be seeing 15 - 25 OHMS from a properly working block heater so my reading from the OEM cord is a bit high.

I am really hoping that someone can help me out with this so that I can be certain that I have a working block heater. Take a read at my issue and tell me if I am on the right track or not. I don't have access to any place warm to park the beast in so I am working outdoors in the cold. I am cringing starting the truck cause I know that I am probably not doing the motor any favors and it's hard on her starting at these temps without a working block heater.

I'm sorry for the long narrative here and I really appreciate your time to read this.

Cheers and Thanks!

Mike
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Re: Q's about Ohms law and block heater

Postby 19trax9519trax95 is online! » Jan 16 2020, 2:30am

Usually block heaters are around 15-25 ohms. Some a little higher, some a little lower. But that's the range I usually see them at.

The factory block heaters aren't all that powerful to the point you'll hear anything. They will keep the coolant sort of luke warm in my experience. If you leave it plugged in and feel the block around the heater is it warm at all?
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Re: Q's about Ohms law and block heater

Postby B52Bombardier1 » Jan 16 2020, 2:51am

Can ANYTHING outdoors at that temperature make something sizzle? That's cold. My oldest son is at Minot ND on work business and its about -18 or so now.

When I lived at Rapid City, SD, my block heater never sizzled. It only made the engine a little lukewarm at those temperatures and didn't get to that lukewarm temperature very quickly.

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Re: Q's about Ohms law and block heater

Postby MacQ » Jan 16 2020, 6:23am

A reading of 34 OHMS on a 400 watt block heater is right on the money. Sometimes you can hear them sizzle other times you can't.

Though it is suggested to let it run 3-4 hours to get things warm, I always left it plugged in overnight.
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Re: Q's about Ohms law and block heater

Postby Used2baFordDrvr [OP] » Jan 17 2020, 6:14am

Hi Folks! I want to thank you all for reading/replying to my post. I decided to plug in last night, including the cord that I repaired for the OEM block heater. I spent most of the morning and early afternoon today snow blowing our place and the neighbors. It had warmed up to a balmy -37* so it took several cycles of blow, freeze, head in to warm up and repeat ad nauseum. I got into the truck mid afternoon and hit the key. Damn! she turned over like a super trooper, started almost instantly. Y'all were spot on in saying that just because I couldn't hear it didn't mean that it wasn't working.

Thanks everyone! Forecast low tonight is -38ish with a wind chill approaching -45*. We are sup[posed to break out of this cold snap next week, thankfully!

Cheers! Mike
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