Can I control the grid heater by installing a switch on the Grid Heater Relay control wires? I know this was talked about before. Did a search and nothing comes up.

i thought about this, but the drain on the batteries would be to great. i wanted to have it to aid in heating the engine up in the winter. i've not found out one way or tother either.

I don't see why not. You'd just have to figure out what each of the 4 wires does. 

I wired a switch in on my uncles 99' because the ECM is slowly dyeing. He cycles the grids with the switch before startup and its much happier. It's been this way for almost 2 years now. 

Find the trigger wires from the ecm. Intercept and run to a toggle.

13 hours ago, JAG1 said:

Can I control the grid heater by installing a switch on the Grid Heater Relay control wires?

 

Yes, you can.  I have had mine wired with a manual momentary toggle switch since the truck was new.  It is simple to do and works very well. Since your truck is an 02, you should be able to use the attached wiring diagram. 

 

Find the two relays that control the intake heaters.  They are located just below the driver's side battery and power distribution center.  You will see the two relays side by side, each with two small gauge wires and push-on connectors.  One wire on each relay comes from the ECM (12 volts when commanded) and the other wire on each relay goes to ground.  Remove the two wires from the ECM side of the relay and protect them from the elements (the wires will no longer be needed).  The wire colors (according to the diagram) are orange with a black tracer and yellow with a black tracer.  Sometimes colors differ slightly.

 

From an un-switched 12 volt source add a fuse, a momentary switch (your choice of location), and enough light gauge wiring to complete the job. The wiring and the switch will only need to handle less than 150 milliamps of current.  Coming from your switch, connect to each exposed terminal of each intake heater relay  The terminal posts are threaded, so you will need to provide a nut with the proper thread pitch for a secure connection. 

 

Codes P0380 and P0382 will be set, but should not activated the CEL.

 

- John

8 hours ago, jlbayes said:

Find the trigger wires from the ecm. Intercept and run to a toggle.

 

Can't. It will throw a P0380 and P0382 error codes if a toggle switch is added. 

 

I just remove the grid heater lead from the positive battery post. I should disconnect mine for the summer. Basically from April to October I leave the power lead disconnected for the grid heater. Any temperature above 32*F doesn't require grid heaters.

Edited April 24, 20178 yr by Mopar1973Man

Can't you just unplug the relay

5 minutes ago, Royal Squire said:

Can't you just unplug the relay

 

This also trips the P0380 and P0382 codes. The only way to do it without tripping codes is to pull the main battery feed to the grids. Anything that breaks the connection of the smaller trigger leads will produce error codes. I know it doesn't light the CEL but it's nice to have to deal with error codes and resetting. By disconnecting the main power lead then the ECM will still do as it pleases will no ill effects of codes or loose wires that might short out. 

Didn't someone earlier mentioned that bad intake heaters can fry an ecm? If it can happen, then I would rather have them on a tugle and prevent ecm from getting cooked. Who cares about the codes, imo. Just thinking out loud. 

26 minutes ago, Dieselfuture said:

Didn't someone earlier mentioned that bad intake heaters can fry an ecm?

 

No. It won't fry the ECM. It burns the fusible link near the battery.

 

14 hours ago, Mopar1973Man said:

 

Can't. It will throw a P0380 and P0382 error codes if a toggle switch is added. 

 

I just remove the grid heater lead from the positive battery post. I should disconnect mine for the summer. Basically from April to October I leave the power lead disconnected for the grid heater. Any temperature above 32*F doesn't require grid heaters.

 

Would likely depend on how you set it up. Potentially yes if you just cut the leads.

Fwiw, there must have been a wiring change somewhere between 99 and 02.  The 99's had the ECM switching the ground.

 

 

If you can disconnect the big lead on the relays, it sounds like you should be able to fake the ECM out with a resistor.  With the right switch, you should be able to pick between Manual On, Auto, and Manual Off.  Frankly, I'm fine with my PCM controlling the grids but can understand someone wanting manual control.

Edited April 25, 20178 yr by Cowboy

Just unhook these wires that's all.

Thats where I disconnected mine. One of the insulating caps on one of the heaters on mine partially melted and have not determined why. No codes have set.

As long as the ECM can see connection to the two solenoid it will not throw any codes. As for disconnecting the wires at the battery the is no power to the grid heater and the ECM can call for heat be nothing happens. Any switch that breaks the trigger leads will set codes but no CEL.

I like this info because on my first gen truck the fuseable links melted. They melted so far into the connection there was barely enough wire to connect the new fuseable links. Had to cut into a rubber factory harness piece to get barely enough to do the repair. 

 

It left me stranded till I got it repaired.

Edited April 26, 20177 yr by JAG1

On 4/24/2017 at 8:52 PM, Mopar1973Man said:

 

No. It won't fry the ECM. It burns the fusible link near the battery.

 

Mine were on for 30min or so and never blew the fuse. It was melting the rubber caps and caused the alternator to quit charging twice. I don't think those fuses should be trusted.

On 4/25/2017 at 1:51 PM, dripley said:

Thats where I disconnected mine. One of the insulating caps on one of the heaters on mine partially melted and have not determined why. No codes have set.

I think codes only get set if the two wires are not connected like moparman said. 

Edited April 26, 20177 yr by TFaoro

So what is wrong with leaving a couple codes on the ECM?

 

Or....... can you get another set of Relays to run your own system on a manual switch and leave the factory relays as dummies for the ECM to not throw those error codes?

31 minutes ago, JAG1 said:

So what is wrong with leaving a couple codes on the ECM?

 

Because if you just disconnect the leads you still take the risk of the leads shorting out and causing ECM damage. The only way is to find two the two black/tan wires and pull them from the solenoids but most can even see the lead colors anymore. Then if anything shorts to the post of the solenoid will cause it to activate next key on. Where if you pull the orange/black or the yellow/black then you have live +12V leads that short out will possibly wipe out the ECM MOSFET's that control the grid heaters. This why I don't bother with that side and just pull the power lead to the grid heater.

 

My way there is ZERO risk to anything and ZERO codes...

 

Edited April 26, 20177 yr by Mopar1973Man

Can you put a battery disconnect switch in those wires?