Grid Heater toggle switch off AND on?

[2002nightmare]

I just finished putting a 95 12V in my 95 Dodge 2500. Replaced the 360 with a 136k mile Cummins and newly rebuilt 47rh. Took the 360 out a month ago and pulled the Cummins out of the shop last night. Being that it had been sitting in a heated shop, I had no problem starting it up. But this morning, after a 27° night, it did not want to start. The grid heaters do not appear to be heating up. I can hear the relays click on/off and the "wait to start" light goes out. This afternoon, I took the grid heater element off my 94 Cummins and we'll see if she starts up tonight after it cools down. I'm wondering if I can install a toggle switch in place of the ECM to manual turn the heaters on. I have read about using a toggle to turn them off when it's not necessary to use them, but can not seem to find any info on how to manually turn them on.

 

[4x4dually]

If you can hear the relays clicking the ECM is sending the signal to turn them on. You either have relays with bad contacts or you forgot to install the ground strap on the grids. It may or may not be possible for them not to ground through the gaskets or mounting bolts, but mine has a ground strap going over to the nearest APPS mount bolts. Does your heaters have this ground? I'd try new relays or borrow some from another truck before I'd butcher the wiring and add more manual crap to something that should take care of its'self. $.02

Try measuring voltage at the grids and make sure you have 12 volts to them. If you do, you have no ground. If you don't, measure the voltage at the relay output. If you do, you have a bad or missing wire between relay and grid. If you don't, you have a bad relay.

 

[zstroken]

I would definitely use a momentary(spring return) switch, to prevent you from leaving it on.

 

[4x4dually]

I would definitely use a momentary(spring return) switch, to prevent you from leaving it on.

True....but it is assanine to even have to wire it manual. The heaters cycle numerous times until the motor gets to the point the ECM tells it to stop. They don't just come on during "wait to start" and then remain off.

Find the problem! Don't riggernigit. Can I say that and remain psuedo P.C.?

 

[zstroken]

True....but it is assanine to even have to wire it manual. The heaters cycle numerous times until the motor gets to the point the ECM tells it to stop. They don't just come on during "wait to start" and then remain off.

Find the problem! Don't riggernigit. Can I say that and remain psuedo P.C.?

Oh I agree find the problem, but if the problem can't be resolved easily, a momentary switch would work. Several have actually put in a pressure switch on the oil system to drop out the grids once oil pressure is up.

 

[2002nightmare]

I agree 100%. I don't really want to manually trigger it, but it the relays are good and the heater element is good...I'm not big on chasing down electrical issues. I swapped the elements today, thats my first hope because I can't be sure that it worked before we pulled the motor. If it does not, I will follow your suggestions. Mine does have the ground strap on the rear inner bolt, but I do not know for sure that it is ACTUALLY grounding. I didn't disconnect any wires on the relays, but there were 3 seperate wires running to the + batt cable and one ground running to the fuse block. Those are back where they came off at this point. Next trouble shoot will be the relays.

 

[4x4dually]

Here's the diagram for an '01-'02 and probably a few other years. Maybe it will help you visualize the whole thing.

First, turn the key on a cold engine and measure voltage at the grid. No sense in combing through wires if you don't have to. See if the hot side has 12V.

Then go from there.