Been a while since I have been on the forum. My block heater is not working. Never had an issue with it but just figured out it is not working and it is in the teens here in Boston. I plow with this truck so need it to start when clod. I verified my source of power (120 volts AC at the end of the extension cord) When plugged in I used my ammeter to look for a load. Zero amps. No breaker tripping so not worried about a short. Next I thought I'd check for voltage at the other end of the cord and if OK I'd ohm it out. Does anyone know what I should see for resistance across the two leads (hot and neutral) at the element?

 

looking to see if the element is OK, not the cord. Looking for correct resistance at the element. Thanks

P.S. I did search the threads for this information but couldn't find it.

 

I honestly have no idea about the Ohm number for a heating element other than it's probably fairly high. Did you check for simple continuity across the element? Have you unplugged the cord from the heater at the block to check for corrosion?

 

Thanks Tim,


I have not had a chance yet to get under the truck. It is caked with salty snow and I honestly don't feel like crawling under there yet. I got the truck started with the help of a heat gun strategically placed. When the FWT gets below about 20 F she doesn't like to start. I may just take the truck to a friend who owns a professional garage and borrow a bay and lift to get to the bottom of this.


Two questions: How common is a defective block heater and Have you any experience with replacing one? I am of course hoping it is just the cord.

 

How do you know its not working? No change in oil temp? The truck wont start?? fwiw my truck starts perfectly in the teens and ive never used my block heater. never seen a need for it. glow plugs do the job. Ive heard we should only really need it below zero. Maybe something else causing a no start??

 

Yes. I know it is not working because my FWT doesn't change. It always went up quite a bit when I used it before. I then put an amp meter on the line while plugged in and got 0 amps. If these elements are 1000 watts I should see around 8 or 9 amps. I may have another issue but When I get the temp up into the 20s it always starts. Below 20 it is a crap shoot. I should probably check my glow plugs and go from there but that ain't happenin until the storms stop. Runs great once it kicks over and I like that it takes less time to warm up.

 

R=V/I=120/8.3=14.5 ohms (in a perfect world).


The most common failure mode is the wire where it meets the plug. Use your meter to see if you have an open circuit between the two flat prongs of the plug (infinite resistance). Then, if you have pointed probes, go back about an inch beyond the plug on the cord and check resistance between the wires there.


If the loss in continuity is at the base of the plug, a quick fix is to cut the plug off and strip back to clean wire and put a new plug on.

 

I had the same problem with mine, I fixed by putting a new male end on it. It wasn't getting juice because the plug was bad. Check the plug first.

 

The male end could have shorted/Melted from bad connection with the salt/road grime. Doesn't hurt to put a new male end, only thing that's ever happened to mine.

Not known for the element to go out, unless faulty

 

^^ Same with mine. Repaired by switching to new male end and then later to Marinco plug mod.