I'm into my first full winter here with my new 2007 HHR LS.

So the block heater has a thermostat that doesn't kick in until -18 C (0 F).

Here are my questions:

When outside temps are -18C or colder:

-does the block heater heat continuously, or does it heat the engine block to a set temperature, then cycle on/off to keep it at that temp?

-what is the temp it tries to keep?

-once the block heater is on, will it kick off if the outside temps climb over -18C?

-which part of the engine does the block heater heat? I've noticed that one very cold morning, outside air temp was in the -26C, I started up and as soon as I toggled over to the coolant temperature display, it read: 5 . . . 6 . . . 7 . . .
etc, as the engine warmed up.

But the coolant in the radiator doesn't start circulating until the engine is warmed up, (around 80 C??? I once tried to figure this out, my coolant temp display went up to 80 C, then dropped to 76 C - I figure that is when engine thermostat kicked in to start the coolant circulating. Engine normally runs at around 89C - as per the coolant temp display).

Okay, lots of boring figures, but curious, nevertheless. Thanks O Great Gurus of All Things HHR!!!

 

From memory, they only heat to a preset temp and shut off.

Is this a freeze plug style?

 

I'm curious, where did you get that info? It sure is not in the owner's manual. Block heaters are usually always on once plugged in, aren't they?
-18C is a bit low, IMHO; experts recommand using it below -10C, to save a bit on fuel at startup.

They heat the coolant right in the engine block.

Anyway, I'll find out tonight; the temperature is supposed to drop low and I'm likely going to use mine for the first time.

Yves

 

I'm curious too, where did you get that info? It might be right, in other cars I have had when you plug in the block heater and listen carefully I could hear it heating, not so on the HHR (Could be my old ears) and yet on some mornings appears to start quickly when plugged in.

Here is something to watch out for. When it first turned cooler last week I looked up where the cord was located and went out to find it, sure enough right where is was supposed to be, unwound and strung it out the front. Cord is quite long and after using the block heater just put the cord back on the lower air valance. Weather turn warmer and did not use it for a week or so and everyday picking up lunch at the grocery store I noticed a piece of a block heater cord in the parking lot. Drove over it a couple of times and thought about picking it up but always forgot. This Sunday went to plug in the HHR, yep no cord, it was mine in the parking lot, fell out and I drove over it and snapped it off. Cord is a lot shorter now with a new plug on it, no fool like an old fool.

 

Good to know about the cord length, mine is still wrapped up and has never been used. This is the third winter for my HHR, the previous ones have not been too cold and my HHR has almost exclusively been in a garage or parkade and never really sat outside in the cold for more than a couple of hours.

 

The owners manual recommends using the block heater when the temp drops below -18C. -18C does seem a bit too cold to start using it.

I know I used mine last year when the temp went below -12C or so.

I haven't used mine yet this winter, even though we've had a few crispy nights so far.

 

As Black Rose found out, the info IS in the owner's manual. Plus, a service person at the dealer told me about it, and added that with the newer cars, cold-weather starting is not as much as an issue as it used to be, hence the block heater being set to go on at 0F (-18C). In addition, I recently noticed a small tag on my block heater cord that says on it that block heater only comes on at -18C. So, the information is quite readily available.

So with all the serious car buffs on this board no one knows the answers to my questions? That surprises me, I had higher expectations from all of you! (Just kidding!)

(And we already had temps down to -30C this year. I'm sure we'll be seeing more of the same as the winter wears on).

 

The info in the user's manual says nothing about how it works or the fact that it might be a closed-loop system.

All it says is: if you have one, use it to help with the starting, but don't bother above 0C.

The other morning, after using mine, the initial engine temp display was around 5C, with outside temp at -23C, so it seems to try to keep the coolant above the freezing point. I'll try it when it's well above -18C to see if it comes on or not. It's too cold now to go check for a tag in the engine bay.

Yves