A New Grid Heater Question

[Lock93]

Did a search of the archives and didn't find an answer to this one. Mornings are now dropping into the 30's, and for the past two days my truck's grid heater won't cycle after it starts, but instead stays on constantly for approx 3 to 4 minutes, then turns off. Volt meter shows it starts, then drops like the heater will cycle (lights dim, etc), but instead of cycling on and off like normal, it stays on and the lights stay dim and meter reads low until its finished, then it turns off after 3 minutes or so. Any advice? Is this normal or ... ? Start up is normal with the "wait to start" (and accompanied whine of the heater) on then shuts off after a few seconds, and truck starts good.

 

[Greenleaf]

That is not normal. Must cycle on/off/on/off after you start. Thinking the temp sensor in the manifold must be working because she comes on at the normal temp reading and shuts down at normal temps. So what determins the cycle thing. Puter?



Scott

 

[Philip]

Take a volt meter and hook it up the the terminal that turns on the relays. See if the computer is telling it to stay on or the relay is sticking.



I had a relay stick on my truck one time.

 

[JLEONARD]

Can't help with the reason it is staying on, but anybody install a switch to turn them on only when desired?

Once I'm started I hate the cycling routine. .

Jay

 

[Squirrel1]

Is that what makes my volt meter drop and pick up again... I can audibly hear something kicking in and out. So this is normal?

 

[Greenleaf]

Yep. My drivers complain that there is something wrong with the alternator. Have to tell them every year this time that this is the norm.



Rusty, er... ... ECJay,



You could wire in a switch. May have to use a relay for the ralays though.



GL

 

[tugboatphil]

As has been proven many times, I'm no genius. But wouldn't there be something built into the heater that shuts itself off after either (a) it reached a certain temperature, or (b) drew current through it for a set period of time.



Standing by for Slings and Arrows!

 

[Greenleaf]

NO. It's programed into the module somehow.



I'm fresh outta arrows. It's deer season. All I have left is . 050 cal lead.



GL

 

[JLEONARD]

But the temp switch in the manifold sends the signal... . I assume it closes when the temp gets low.

So wouldn't it be a relatively simple matter of putting an on-off switch in line to interrupt the signal to prevent the grids from comming on?

Jay

 

[Greenleaf]

Yes, but the temps would have to be low enough to "come on" when you throw the lever to activate the suckers. I was thinking by-pass the temp sensor in the manifold to have complete control over the situation. But the puter is still in there turning them on/off/on/off.



I could resort (hate to do it) to looking in the FSM for details.



Um, on second thought my truck ain't got no grid heaters, so what the heck do I need to know for?



GL

 

[JLEONARD]

But the puter is still in there turning them on/off/on/off.

If the signal was interrupted from the temp switch, the "puter" would think it was warm and not cycle.

Is that correct?



I just want to be able to shut the grid off on those days with the headlights on, turn signal on, when I need the wipers too. The voltage gets so low that the wipers barely move... I'm concerned with burning the motor up in that situation..... or the headlight switch for that matter.

Plus once I'm going down the road what do I really need the grid heater to do for me?

 

[Greenleaf]

The incoming air has to warm to (I think) 60° before the grids stop cycling. I could look for ya if'n u want. I don't recall the temp in which the switch is activated.



-S

 

[JLEONARD]

My book says 56 deg F (13. 3 for the Celcius crowd)