How to know if your Block heater is working ?

Sir Dan · January 24, 2012

I know that the new enviro friendly "green" block heaters they use now don't work nearly as good as the old "always on" type. These new ones are thermostatic controlled and only kick on at extremely cold temps. and only for a short time...worthless IMHO.

dewfpo · January 25, 2012

and only for a short time.

What makes you say that? I opened up the block heater thermostat on my '05 and it was only temperature controlled (bi-metal spring).

DEWFPO

Sir Dan · January 25, 2012

It will only run long enough to bring up the temp of the coolant nearby to like 0 deg. so that's not very long as compared to always on. Some people have figured out how to bypass this and then they get a check engine lite because the OBDII computer gets confused at the higher coolant temp at start up. Some emissions control crap I guess.

Wires · January 25, 2012

It's probably not get messed up, they just tag it since the coolant is much warmer than the incoming air "for stattisical purposes:". It should normally just deal with the temperatures.

Apparently the manual said the it doesn't kick in until below 0F / -18C. That's pretty cold. Maybe it's not really needed above that temp, but cold starting a dry engine in the morning does accelerate cylinder wear a lot (unless modern oils are that much better than stuff from 20 years ago).

Morgan1986 · January 25, 2012

well my oil is like good to -45 C I think i was reading on it . I Still plug in

dewfpo · January 25, 2012

MIne ('05) used to have the bi-metallic sensor to only allow it to come on in ambient temps 0F or colder (regardless of coolant temp). I bypassed that and it comes on whenever I plug it in. I've never tripped the dash MIL because I don't plug it unless it is in the teens or colder out and I don't leave it plugged in overnight. I understand that as part of the OBDII standard emissions test (for certain GM vehicles), the ECM compares the engine, transmission and intake air temp sensors for consistency on certain COLD starts (COLD meaning the engine is off for a certain number of hours min.). If one of the sensors is off by more than a certain amount it will trip an MIL telling you the ECT sensor is bad. The MIL will reset itself after a certain number of new cold starts if the sensors are within range.

DEWFPO

Morgan1986 · January 25, 2012

how did you buy pass that ?

dewfpo · January 26, 2012

The first time I partially cut the rubber on top of the thermostat to expose the bi-metal spring. I then just stuck a small metal washer in there to make constant contact, flipped the rubber back over and wrapped with electrical tape. Worked like a charm. The second time, I just went to NAPA and picked up a replacement cord without a thermostat and swapped cords. Very easy.

DEWFPO