Block Heater Problem - 2020 Sierra 1500

[NorthernX31]

It was -38C last night and my truck took four tries before it would start this morning. I checked the power at the end of the plug and there is 120volts. When I plug it into the truck, there's no amp draw. I suspect the chord between the truck and the block heater is broken. Is this a common problem? Am I able to replace this with a standard HD extension chord without any problems?

[latreille89]

5 hours ago, NorthernX31 said:

It was -38C last night and my truck took four tries before it would start this morning. I checked the power at the end of the plug and there is 120volts. When I plug it into the truck, there's no amp draw. I suspect the chord between the truck and the block heater is broken. Is this a common problem? Am I able to replace this with a standard HD extension chord without any problems?

The heater plug in your bumper plugs into another harness behind the bumper. It has a thermostat built in. I'd suspect it's the thermostat that's the issue. You can order the harness and install, nothing too difficult as you already have the layout of where it needs to be. 

[Mike Duhaime]

6 hours ago, NorthernX31 said:

It was -38C last night and my truck took four tries before it would start this morning. I checked the power at the end of the plug and there is 120volts. When I plug it into the truck, there's no amp draw. I suspect the chord between the truck and the block heater is broken. Is this a common problem? Am I able to replace this with a standard HD extension chord without any problems?

#1 issues is wire breakage at plug, you know, where it's yanked on instead of using 2 hands to separate. Get a volt/ohmeter. Simply put leads on plug end. There should be continuity, and about 5 -15 ohms indicating the plug is on the block heater and there is a circuit. Block heater cords are available at Napa.  In a pinch, a magnetic block heater will work...just put on outside side of block. Replacing the block heater is a garage job for sure

[GMCustomerService]

8 hours ago, NorthernX31 said:

It was -38C last night and my truck took four tries before it would start this morning. I checked the power at the end of the plug and there is 120volts. When I plug it into the truck, there's no amp draw. I suspect the chord between the truck and the block heater is broken. Is this a common problem? Am I able to replace this with a standard HD extension chord without any problems?

This is certainly not what we like to hear, NorthernX31.  Please know, customer satisfaction is extremely important to us. Our team would be more than happy to take a closer look into the concerns with your 2020 GMC 1500 SLE. To do so, please send an email to [email protected] with ATTN: NorthernX31/GM Trucks in the subject line.

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[NorthernX31]

Thanks for the responses. I found a warm garage to keep the truck in overnight and am going there now to see if |I can locate a break in the harness between the bumper and the block heater. I did check for continuity and resistance at the bumper yesterday but found none. I'll post what I find.

[NorthernX31]

Merry Christmas. I went out today and confirmed that my block heater is pooched. The wiring behind the plug in the bumper is accessible by removing some T15 screws from the inner fender and bending it out of the way. There's still a bunch of plastic in the way but a person can at least see the wiring and the thermostat After this it runs out onto the frame and then over to the block heater. There's a metal clip that has two locking tabs which need to be released in order to unplug the cable from the block heater itself This was pretty challenging for me at least but I used two picks to hold the clips back to get the plug out. There is an open circuit between the two leads on the heater so it's done. Kind of bummed out that this has happened on a 2020 after my bumper to bumper warranty has expired. Plus its -35 outside so that doesn't help. On the bright side a block heater should be fairly cheap