Engine/Transmission (1994 - 1998) Grid Heater Disconnect

[skinnee440]

This question has probably been answered before and if it has please let me know where as I couldn't find it. I want to put a switch in my truck, '98 3500 4x4 w/12v, to disconnect the relays from cycling once the truck has started. During the summer I just unhooked them at the relay as I got tired of them cycling when it was in the 60's. Being in northern NY I need them occasionally. I have the factory manual and have looked through the wiring diagrams with great distaste. According to them there is a splice point somewhere that would be good to tie into, but where is it? What I want to do is just run one wire to a switch under the dash to be able to shut off the relays. Any help is greatly appreciated!

 

[fest3er]

According to my '98 manual, there is no splice in the relay control circuit, but there is a splice that feeds power to the relay controls, S-130, which is probably what you want. According to the manual (8W-95-3), it is located on the engine harness that crosses the top of the firewall and appears to be on a 'descender' to the (passenger side) of the shutdown relay (and former location of the fuel heater relay).

The wire(s) will be light green with black tracer (LG/BK), as are a couple other wires; you'll have to meter the wire to be sure you're getting the right one. Your switch will interrupt power to the control side of the relay. (The PCM completes the circuit to ground when it wants the heaters on. )

 

[skinnee440]

Thanks for the info, yes that is the splice that I was talking about. Sorry I did not get that technical. I will dig into it tomorrow and see what I find. I also thought about finding a resistor that would trick the PCM into thinking it was warm enough not to cycle the grid heaters and rig it into the circuit and use the switch to switch between the false reading and the temp. sensor in the intake.

 

[fest3er]

Thanks for the info, yes that is the splice that I was talking about. Sorry I did not get that technical. I will dig into it tomorrow and see what I find. I also thought about finding a resistor that would trick the PCM into thinking it was warm enough not to cycle the grid heaters and rig it into the circuit and use the switch to switch between the false reading and the temp. sensor in the intake.

It'd be better to interrupt power to the relay controls. No sense in affecting any other systems, you know... .

 

[GAmes]

On a 97 power is supplied to the relays continuously and the PCM provides the ground to activate the heaters. I don't know if the 98 is the same. I unplugged the ground wires from the PCM and secured them. One wire with two connectors (one on each relay) goes to one pole on a toggle on the dash, the other pole has a wire to a grounding point under the dash. Only one downfall to this installation. If I forget to turn the switch off, or accidently turn it on while driving, the current draw overloads the alternator and the PCM kicks it off line. The fix is to pull over, shut the engine off for a few seconds and start it back up. In the last 7 years I've had to do that procedure about 5 times.

 

[radixr]

I don't understand what the problem is. If the grid heater is cycling, just put it in gear and go. They shut off once you reach 5-10 MPH.

 

[GOTSOOT]

dont need to wit for the light to go out, after the first time you start in the am,unless you let it sit allday. shuts off after 10 or 15 mph!

 

[skinnee440]

Thanks for the replies

GAmes they are the same. Thanks for the info. I have considered doing that also. I understand that it shuts off after a certain MPH. I hate the extra strain that it is putting on the charging system and the batteries. I do not live in a warm climate!!!!#@$%! Every time my truck is started, unless it is about 70 or more, which is not very often in the last year, they cycle. Slow wipers, dimming lights, it is a big nuissance to me. Not to mention there are times when I leave the radio on when working on a job (cb and stereo) and need all the amps that I can get.

 

[GAmes]

I'm not always in a warm climate. I cycle the heaters for as long as the wait to start light is on. Turn the toggle off and start the engine. No aggravating heater cycles, and I also like it when I need to turn the key on for something other than starting. It is an easy bomb.

 

[Vaughn MacKenzie]

I got irritated at mine always coming back on even when the engine is warm but I only stopped for 10 minutes. Just totally disconnected them. Engine always lights off instantly and smoothly down to about 10 degrees, and will start down to about 0 on 1 battery without being plugged in. Grids are pointless above 15F IMO.

 

[RVPILOT]

grid heaters

I agree with Vaughn, worthless unless you live in Canada or Alaska, I disconnected mine at about 750,000 miles and started it up in 6 above in Truckee ca. took alittle turnin but it got started. this with all these miles, should be no problem with less miles. Stormy

 

[CToney]

I put a switch on the ground wire from the relays to the oil pressure port on the filter housing so once I had oil pressure the grids wouldn't work. Do a search and you will find info on this. Relays are only good for so long and they are not cheap. They will last a lot longer if you do this.