Block Heater Cord Modification

dewfpo · December 10, 2006

For those of us with gas engines and the stupid Zero Degree thermostat in the Block Heater Cord.......

Finally got it done today. Tried cutting the 'blister' off the plug with a new utility knife blade - no dice, then a razor blade - no dice. The black rubber/plastic is too hard. Broke out the Dremel tool with a cutoff wheel and cut, then pulled the black/plastic 'blister' off, then pulled the small silver 'tin can' off with some channel locks (tried not to crush it so I could re-use it). That exposed the thin metal sensor. I pushed down on the sensor and it stayed down (to my surprise). I plugged it in and it worked. I then stuck a very small, thick, rubber O-ring I had laying around into the cavity on top of the metal sensor (to make sure it stays down and in contact), put the silver metal 'tin can' back on top of the thick O-ring, then the rubber cap I cut off back on top of the 'tin can', then I wrapped it all with 'Cold Shrink Tape' so that it keeps pressure on the cap and makes it weatherproof. Works great.

One happy camper now.

DEWFPO

MS3DALE · December 10, 2006

I'm going to have to do that with mine.

I wish you would of got some pictures,I'm scared I'm going to cut the "blister" in the wrong place!

teambell · December 10, 2006

Sorry to be a bother, but what is the stupid Zero Degree thermostat in the Block Heater Cord? I have an 8.1 / Allison, but not sure about the block heater cord. I have seen the ones used for diesel, is it the same?

Thanks!

Trouttrooper · December 10, 2006

Sorry to be a bother, but what is the stupid Zero Degree thermostat in the Block Heater Cord? I have an 8.1 / Allison, but not sure about the block heater cord. I have seen the ones used for diesel, is it the same?

Thanks!

<{POST_SNAPBACK}>

GM started putting thermostat operated plugs on the block heaters to prevent them from turning on until outside temp dropped below zero F. Something to do with emissions. Don't remember what year that started but since I'm assuming you have a 2002 you might not have one (if you have the heater). Easy way to tell is look at the cord. If there's a "tumor" near the plug end then you have the thermostat.

DEWFPO......

dewfpo · December 10, 2006

I'm going to have to do that with mine.
I wish you would of got some pictures,I'm scared I'm going to cut the "blister" in the wrong place!

<{POST_SNAPBACK}>

No worries MS3DALE. I just used a Dremel tool with an abrasive cutoff wheel to cut the raised blister at the shoulder all around. There is a silver metal cap under the black plastic that will stop you from cutting too deep. You will see the shiny silver as you cut down into the plastic. You really can't damage anything. After you cut around the plactic cap, pull it off or pry it off with a screwdriver. Mine came off and left the silver aluminum cap behind, so I used vice grips to pull it off. It's very thin metal so don't gorilla grip it with the vise grips if you want to reinstall it. I bent mine a little getting it off but I bent it right back into shape. The metal is as thick as a pop can. I reinstalled mine, but you don't have to. (Under the tin cap is a hard black plastic that will break when you pull off the tin cover. No worries it doesn't create a problem.)

Now that I've done one, it's fairly simple and could probably do in about 20 minutes. It helps to get yourself something to sit on while your cutting the blister off. (I have my cord coming thru the opening in the bumper on the driver's side.)

You could use metal washers to keep pressure on the bi-metal spring but I liked the idea of a thick rubber O-ring better (it's compressable). The O-ring or washers need to be LESS THAN .5 inches O.D. to fit inside the blister case.

One last thing, test your work before you do the final wrap with tape in case you need to make any adjustments.

DEWFPO

MS3DALE · December 10, 2006

Thanks dewfpo,I actually have an extra cord that I'm going to try and modify,wish me luck!

ArcticJ · December 13, 2006

Happy Holidays my tumored block heater friends...

dewfpo - have you used the heater yet and if so, in what temps and are you getting any codes?

As I posted last year, I cut one of my trucks plugs and shortly thereafter, i was throwing the P0116. I used the heater after it went down to 8 degrees above and it still threw the code.

I am now AGAIN looking for a better solution for my other truck as well as the cut one...

I might add that last year I asked one of the techs on this site about a reprogram of the diagnostic process....I was met with a resounding NO

FYI, I found that GM issued new software for diesels to modify the diagnostic process to decrease the likelihood of p0116 and others by changing the air intakes used for comparisons during start-up diagnostics...

problem is I dont have a diesel

dewfpo · December 17, 2006

Happy Holidays my tumored block heater friends...

dewfpo - have you used the heater yet and if so, in what temps and are you getting any codes?

As I posted last year, I cut one of my trucks plugs and shortly thereafter, i was throwing the P0116. I used the heater after it went down to 8 degrees above and it still threw the code.

I am now AGAIN looking for a better solution for my other truck as well as the cut one...

I might add that last year I asked one of the techs on this site about a reprogram of the diagnostic process....I was met with a resounding NO

FYI, I found that GM issued new software for diesels to modify the diagnostic process to decrease the likelihood of p0116 and others by changing the air intakes used for comparisons during start-up diagnostics...

problem is I dont have a diesel

<{POST_SNAPBACK}>

Been gone for the 6 days (Vega$)

Of course since I modified the plug, the temps have been up in the high 20's so I haven't had the need to use the block heater. We've got a cold front that moved in during the night and it's supposed to snow for the next 4-5 days. Typically when it snows like this it's 'warm', like it is now 31F so I still won't need the block heater for a while.

My understanding is it may set a code, but it doesn't affect engine performance and if the code isn't set after a certain # of starts, then the code goes away. So I don't see any problem with this. If I am wrong someone please correct me.

DEWFPO

fossil · December 22, 2006

Correct, it will possibly set off a code and trip the check engine light. Maybe some cold weather driveability issues because the computer senses warm coolant temps but very cold ambient air temps. That block heater cord is designed like that for a reason.

dewfpo · December 22, 2006

So far so good, no codes, no problems and the truck is starting right up and heat is available.

DEWFPO

dewfpo · January 18, 2007

Update : I've been using it day after day and not having any problems or throwing any codes other than I cannot explain why the 1,200 watt block heater is only pulling 384 watts.

DEWFPO

Trouttrooper · January 20, 2007

Update : I've been using it day after day and not having any problems or throwing any codes other than I cannot explain why the 1,200 watt block heater is only pulling 384 watts.

DEWFPO

<{POST_SNAPBACK}>

does it seem to be working enough to help?

I wonder if you don't have a good connection where you modified the tumor.

dewfpo · January 20, 2007

It is working when plugged in, it makes the typical funky noises. After about 4 hours at +15F the gauge will slightly move off the 160F peg when started.

I thought about the modified tumor, but the way it's set up, it's either on or off, there's no gradation. I even squizzed harder on the tumor to see if it might make a difference on the amp gauge and it did not.

On another similar note.... I just bought an FJ cruiser to go off-roading with. I installed a Toyota block heater in it and there were no warnings about using it above 0F and I've used it every night for the last 6 days without any codes or dash lights.......and this block heater is for 8 different models of Toyotas going back as far as 2003.

DEWFPO