Intake Grid Heaters

[Turbo Terry]

Like a dummy I turned the key on to roll the windows up and left the ignition on all night. In 20 years of owning this truck it never happpened before. As luck would have it the truck started in the morning. Which was good as I was some what remote and off the grid. So did I damage the intake heaters and why didn’t they drain the battery ? And how do I test them good with a multi meter??

 

[GAmes]

How warm was it?

PREHEAT CYCLE
The PCM will supply a signal to the 2 relays when
the ignition (key) switch is initially turned to the ON
position. When this signal is supplied, electrical current
is passed through the relays for operation of the
2 heating elements.
If the intake manifold air temperature is 15°C
(59°F) or below, the air heater elements are energized
and the wait-to-start warning lamp is illuminated.
The heater is energized for a specific amount
of time. Refer to the following Air Heater Cycle Chart
(Fig. 7) for a temperature/time comparison of relay
engagement.
Once the heater has cycled, the wait-to-start warning
lamp goes out.
While the engine is cranked, the heater relays are
not energized.
POST-HEAT CYCLE
After the pre-heat cycle is completed, the PCM
must receive an engine crank signal (engine speed
between 32 and 475 rpm) followed by an engine run
signal (engine speed above 475 rpm). Intake manifold
air temperature must also be below 15°C (59°F). All
of these signals must be seen by the PCM before initiating
the post-heat cycle.

 

[Turbo Terry]

70-80 f. So they never came on maybe and never stayed on good to know. Thanks

 

[GAmes]

Even when it is cold they don't stay on. You can test them this winter when you need them.

 

[DavidC]

When I spent a couple of Winters in Vermont I would be very cautious at -20 and cycle the grid heaters 3 times. Each one required the cycling of the key.