[rbarrios]

hey red- if you still have your Trailblazer... you may want to check out trailvoy.com
I hang out over there--- all you want to know about Trailblazers, Envoys, and the other GMT-360's.

I remember reading over on the trailblazer forum- that some members who had the block heaters- Not sure if they had aftermarket or factory....but they would use those timers that you can plug in-- and set it to come on at x hours before they were to head out.......

 

[rbarrios]

I dont have a plug heater- device- as I live in LA..

But I have head- about the heaters with the switch in the plug- that will only turn on at 0 or so.

 

[rbarrios]

this answer the question...

Block heater on GM vehicles
GM has installed temperature sensing circuitry into the plug on factory installed block heaters. It prevents the heater from operating unless it is colder than 0°F or -18C. It may seem insane, but it really does make sense if you understand why. If you install an aftermarket block heater without this circuitry, the PCM will see warm coolant, but a cold engine and cold air coming into it. Remember, it's the PCM's job to determine the correct air/fuel mixture. A cold engine block and cylinder head act as a fire extinguisher when you first start up the engine. So the computer commands a very rich mixture. How does it know what temperature the engine is? It used to look at only the coolant temperature. But now it looks at both coolant temp and the temp of the metal itself. If it see a discrepancy between the two numbers, and the outside air temp coming in through the intake is 0° or above, it assumes there's something wrong with the coolant temp sensor and sets a trouble code.

Bottom line, if you add an aftermarket heater, it must have the temperature sensing circuitry in it or you WILL set a trouble code. Also, if you ever have to replace the power cord to the factory block heater, you must use a new GM power cable

 

[rbarrios]

you want the Traverse block heater pic? or any to see what is being talked about?

 

[rbarrios]

is that a reason why many semis when parked in cold areas- leave the engine running instead of shutting down?

 

[rbarrios]

I had figured that fuel use/cost/comfort while idling was smaller- than shutting down- then trying to start a cold diesel engine.

 

[rbarrios]

neat.!