Testing Block Heater
Thread Starter
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Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
Testing Block Heater
I think the block heater in my 91 7.3 has burned up. Plugged in all night and the engine is cold. Not even any warmth on the heater end of the power cord. Stuck in the drive! Thanks.
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Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
No sign of that really. I do know that the truck side of the cord did use to get warm to the touch. Is that normal?
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Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
What should that resistance be? Thanks.
Posting Guru
Joined: Dec 2009
Posts: 1,615
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From: Hagerstown, Md
sorry bout waitin so long to get back to ya if you have a volt meter set it the 20 on the ohm and touch the 2 top pins on the male side of the block heater cable and if there is any resistance than it is good if not than you need a new cord
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Block heater come in a variety of wattages.
Because of that, resistance can vary.
26.4 ohms = 500 watts
13.2 ohm's = 1000 watts
8.8 ohm's = 1500 watts
That is three examples, I have seen 600, 750, 900, 1200 and several other wattages over the years on top of the ones I listed above.
Because of that, resistance can vary.
26.4 ohms = 500 watts
13.2 ohm's = 1000 watts
8.8 ohm's = 1500 watts
That is three examples, I have seen 600, 750, 900, 1200 and several other wattages over the years on top of the ones I listed above.
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Mountain Pass
Joined: Mar 2004
Posts: 102
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From: Wilmington, NC
With my ohm meter set at 200 (the lowest I can get it) I get no response at all. I tested it on an air compressor plug with the same setting and it did read. That mean I need a new cord?
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Posting Guru
Joined: Dec 2009
Posts: 1,615
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From: Hagerstown, Md
yes and your local napa store will have them or can order them in they are either a 5 foot or 6 foot cord no more than $20 i believe mine was $15 when i got mine. it is much more common for the cord to go bad than the actual heating element itself
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Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
Thank you.
Elder User
Joined: May 2008
Posts: 508
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From: Wasilla, AK
Unplug the cord from the block heater and bench test it. I've found many of these cords break right at the male end you connect to the extension cord. If it has continuity check the freeze plug for continuity. Sometimes the cord is not making good contact with the freeze plug prongs. If the freeze plug shows 0 continuity replace it. I use a 600 watt up here. It warms up my old 1984 6.9 or my 1991 7.3 enough in 30-45 minutes to start at -20.
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Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
Hi Dave. What is the test criteria for the heater itself? Thank you.
