Block heater doesn't work.

[SHOPMAN426]

A freind of mine has a '01 LB7 that he did buy used. From day one since he has had it, the block heater hasn't worked. I looked though the owners manual for him and I can't see that there is a specific fuse for the heater. Does anybody have any thoughts on what could be wrong?

Thanks,

Shopman426.
Mike.

[DmaxMaverick]

The heater has no onboard electrical circuit. The heater element is independent of any system on the truck. The cord plugs into the heater element, so if it's not working, inspect the cord for damage, and make sure it is plugged into the element. There's nothing sophisticated about it. It is just a heater element with an A/C cord attached.

[SHOPMAN426]

Thanks for the help, I will pass it along to my friend. He needs the heater since he lives up in northern Idaho.

Shopman426.
Mike.

[Mark Rinker]

When it used to get cold and snow in Minnesota, my elements would only last about 2 seasons before burning out. I left them plugged in alot. If it was a cold weather truck, it may simply be toast from lots of use by someone like me that likes warmer starts.

Its January 3rd and nothing I own has needed to be plugged in this 'winter'. Unreal.

[Willcoc]

I thought my heater was toasted but it was just the cord end. With a ohm meter, I had no resistance at the cord end. I then used a set of insulation peircing probes and found that I had resistance just after the cord end. Replaced the cord at worked fine last winter. Used only one this season so far.

[SHOPMAN426]

Well, my buddy finally crawled under his rig the other day to chase out the block heater cord to it's end. He found it just hanging in the wind. The problem is he can't plug it back in because it is all melted as if it got too hot and as it got soft and gooie, it just fell off. He talked to a friend of his in Idaho and he knew of a guy with a '05 that caught fire and burned the front of the truck to the ground. Does GM have a problem here? Or are these few cases freak accidents. It almost sounds like if you use the block heater alot this is the end result. I took a look at my own and noticed that the plug cord is only 18 gage wire. That seems a little small for this type of application.

So now that his '01 block heater is of no use, what are the options? Can you replace the block element? Or is this something that should be left to the service tech. How big is this heating element in the block?

Thanks,
Shopman.
Mike.

[FisherDude]

I was having a few pops with a GM mechanic last week, and he said a common complaint is that block heaters aren't working. However, he said they (at least on my truck) won't kick in until -18C (that's 0F for our friends south of the 49th). He said with the pre-heaters and such, don't worry about it. I've only heard mine working one morning when it was -20C. The truck has started perfectly every cold day for me.

[Mark Rinker]

Starting the engines that cold is tough on them, IMO. Electricity is cheap by comparison!

[FisherDude]

I agree Mark. I've kept it plugged in every night just to be sure. I wonder why they put the -18C thermostat in them? It would make sense to have them warmer for starting.

[speeddrive1]

BS. The block heater will work even at 80 above. There is no thermostat on them.

[FisherDude]

BS. The block heater will work even at 80 above. There is no thermostat on them.

Thanks for your friendly, helpful reply. My truck has only 1200 kilometers on it, so I must assume the coolant heater is in good shape. It's -12C this morning, I just checked and my block heater isn't running. The only time I have heard it was on a -20C morning. I would be surprised if the local dealership's GM diesel mechanic who works on these trucks every day was incorrect. I would also wonder why my owner's manual says, on page 11 of the "Duramax Diesel Supplement", and I quote:

"Engine Coolant Heater:
In very cold weather, 0F (-18C) or colder, the engine coolant heater can help. You'll get easier starting and better fuel economy during engine warm-up. Usually, the coolant heater should be plugged in a minimum of four hours prior to starting your vehicle."

Perhaps the '07 LBZ models are different from your '01 LB7, as the LBZs have a different intake heating system, or perhaps Canadian models are different from the US models. In any case, I still believe mine is thermostatically controlled.

[speeddrive1]

How do you know that it is not working, did you feel the block to see if it is warm. Have you checked to make sure the cord is not unplugged from the element? A block heater consist of an electrical cord and an element that fits into the block, there is no thermostat, the ecm has nothing to do with the blokcheater for a reason. If block heater shorts out wich many do, it would fry the ecm. Dont believe me crawl under truck and check it out.

[SHOPMAN426]

Ok guys, you are getting off the topic a little. The question was for an '01 truck, and that the block heater is not working because the cord end at the heating element is melted as if it got so hot, that it got soft and lost it shape and dropped off. The problem now is what to do, replace the cord or replace the cord and the element? Do you have to pull the soft plug or can you remove the block heater element only.

Shopman,
Mike.

[YZF1R]

As others have stated, no t-stat. It's just an emersion heater, the same kind that you dunk into a cup of water to heat it up. Just as was pointed out in the manual, at 0 degrees your truck may start better with it plugged in. Nothing about plugging it in year round and when it's needed a t-stat will turn it on or off for you. No biggy, just take a look at the wording in the manual again more carefully.

Steve

[YZF1R]

Shopman426, Looks like we posted at the same time. You would need to ohm out the heater to see if it's any good. I don't know what it should read though. I think most people just replace the cord. If you remove the heater, you are opening the coolant passage. They have all been basically the same forever. The only difference is the wattage and shape. They need to be shaped to fit into the coolant cavity of the engine they are designed for. Cummins, Detroit, Cat, pickup/car deisels, stationary, offroad, etc.

Steve

On edit: You could ohm out a known good one and then you would know what yours should be.

[cwood]

I was told when I bought my 04 LB7 that if it was above 0 and i plugged it in that it could set of some trouble codes I tried it any way and never had a problem. Three nights ago plugged in my new 06 LBZ had no problem, then two nights ago plugged in again since it was in the single digits truck seemed to shift weird but didnt think a whole lot of that, but the next time i started the truck the check engine light was on it had set of four codes. when I called the dealer and read him the codes the diesel tech asked if I had plugged in the truck the nite before he then told me that if it is not below zero and its plugged in it can set off these engine codes which disables some of the temp sensors the truck then runs off of a pre programmed set of temps which makes the truck think it is always cold this explained the weird shifting. he also said that they could give me a different cord and reprogram the truck to be plugged in if above zero. I had the codes cleared and truck runs fine. dont know if this is true for the LB7 also might be something to check out before buying a new cord or element.

[Idle_Chatter]

Shopman426, Looks like we posted at the same time. You would need to ohm out the heater to see if it's any good. I don't know what it should read though. I think most people just replace the cord. If you remove the heater, you are opening the coolant passage. They have all been basically the same forever. The only difference is the wattage and shape. They need to be shaped to fit into the coolant cavity of the engine they are designed for. Cummins, Detroit, Cat, pickup/car deisels, stationary, offroad, etc.

Steve

On edit: You could ohm out a known good one and then you would know what yours should be.

I was given 13 ohms as a good reading for the heater. I had to replace the heater cord plug on mine today and it ohmed out at 13.4 - I'll know for sure at 0530 in the morning at -8 F if it works.

[speeddrive1]

When you check the element you have to make sure there is no resistance through the hot side and the groung prong on the element( center prong) . If there is any resistance through the ground the element is shorted out and needs to be replaced.

[SHOPMAN426]

Thanks guys, I will pass this info along to my friend with the '01.

Shopman.
Mike.

[YZF1R]

Thanks for the 13 ohms Idle_Chatter. I'll need to note that. Also, good point by speeddrive1.

Steve

[JohnC]

The main reason the cords fail is water and road salt gets into the connection and corrodes the contacts. This causes resistance in the contacts which generates heat and melts the housing. When you replace the cord, polish the contacts on the heater element and apply a liberal dose of dielectric grease to exclude the moisture. As someone pointed out, they could get hot enough to cause a fire.

If the element fails it will either fail open (infinite ohms) or it will short to ground. Use a GFI protected circuit to be safe.

[crafty]

A good investment is to buy one of those circuit testers that plug into the line. (plugrite is the one brand name that I have.) It has two lights, a red and a green that tells you if you have power and if the circuit is good.
My block heater quit two years ago. I was blowing the fuse in the panel every time I used it. The first time the dealer replaced the cord. The second time (a week later) when it quit again, they replaced the heating element and cord. That time it had melted the cord off at the plug. It seems that the element made contact with the block and shorted things out. This seems to be a problem in alot of the older ones at least. I would certianly replace the whole assembly. :D :D :D