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As stated. Now that the cold weather has set and it is regularly below 40 in the mornings, when I turn my key to “On”, the “Wait To Start” isn’t illuminated. So I start it and the grid heaters DO cycle. Who knows what this means? I did replace the batteries a few weeks ago for not holding a charge.


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The intake air sensor (IAT) on top of the intake manifold sends the signal to the PCM that activates the light and the heaters. IIRC there is a ohms test in the FSM for it.
 
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Is the battery voltage dropping? You should be able to hear the relays click on.

Once the truck starts, the heaters cycle as normal.


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Is the battery voltage dropping? You should be able to hear the relays click on.

Once the truck starts, the heaters cycle as normal.


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When you key the truck on, you should hear a click and the voltage should drop. Then after the timeout you will hear another click and the voltage will increase. (That's when the wts light normal goes out)
 

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When you key the truck on, you should hear a click and the voltage should drop. Then after the timeout you will hear another click and the voltage will increase. (That's when the wts light normal goes out)

I don’t ever recall hearing that initial click ever. But the second click definitely never happens. I’ve waited longer than I ever have waiting for it. Never happened. But why would they work once the truck starts?


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The last time I didn’t hear the solenoids click was when my buddy complained his batteries were running down alarmingly quick.

Turned out to be solenoids stuck in the “on” position.

Also, sometimes, a solenoid on its way out will barely click so may be hard to hear. Try keeping the blower fan off, belt latched in, etc, so there’s no audible distraction.

Also, check if the fusible links in the power feed to the solenoids are good. May as well unwrap them & check for signs of corrosion. A bad fusible link may not play well with a battery's static voltage, but may well have any resistance overcome by the higher charging voltage when the alternator is running.
 

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Discussion Starter #9
Awesome. Thanks man. I’ll check that when I get back home next week.


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The 'wait to start' (and WIF, CEL, GEN, ABS... Airbag too? I can't recall the whole list offhand, but all the ones the PCM controls directly) lamps should light for a moment at key-on regardless of whether or not the grid heaters are actually turning on. It's a bulb check. If any of them don't light, either the bulb is burnt out, the wiring between the PCM and the bulb is messed up, or the PCM is broken... in order of likelihood.
 
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