Engine/Transmission (1994 - 1998) Grid Heaters Wiring Momentary Switch Instructions

[MMcCallie]

My Excursion has been starting fine when indoors, but now it is being parked outside and won't start. Even around 20 degrees, it wont start without a tiny shot of ether. Unable to plug it in at night. The grid heaters have not been connected because i'm not using the Dodge harness.



I'm looking for instructions on how to custom wire my grid heaters. I bought a momentary switch and an LED but do not have any relays. Can i use just one relay to hook up both grid heaters? What size relay should i use and where should i buy it? Is 10 gauge wire heavy enough to go to the grid posts or do i need something bigger?



If possible, please post pictures that will show me which wires should go to which posts. I'm looking for as much detail as possible. I'm not near my truck, my dad is trying to make it run as his daily driver so i will be passing on the information. Wondering if i should try installing a glow plug in the intake tube as well. Needs to reliably start in -20 degree weather.



Much Thanks,

Matt

 

[FordCummins]

Hmm, sounds like something is wrong if it wont start at 20 degrees. But anyway, to help you get your grid heaters hooked up. Get a relay like the Stancor 586-902 available at http://alliedelec.com/ for a very reasonable price. Its setup to handle 200amp continuous, 600 max, which is more than adequate for the grid heaters, which I believe draw 90A EACH. SO you are at 180amp, still under the continuous duty rating of the Stancor unit. Run a heavy + wire to each of the posts on the grid heater block, setup the relay to be activated by your switch, and you will be all set. If the Excursion was a PSD to start with, you could even tap into the GPR relay activation wire from the factory PSD harness, so it would operate just like normal, with the "WTS " light coming on and being in sync with the grid heaters.

 

[MMcCallie]

Well, it's been in the teens when he's been trying to start it. Plugged it in for 6 hours today and tried it when it was in the upper 20s and it started immediately.



I really like the idea of having everything automatic, in sync with the Wait To Start light. I kept the old glow plug relays from the PSD. Do you know what PIN # in the Ford harness to use?



I'm not sure if there are any temperature inputs still being fed to the PCM. Would they cycle fairly frequently as did the glow plugs? Is it nicer to have control over them with a switch? Any further advice or instructions would be great. Thanks.

 

[FordCummins]

I wouldnt use the old glow plug relays, they have a habit of burning out in the PSD applications, and all those guys upgrade to that Stancor unit I mentioned earlier. I think the PCM uses an oil temp sensor, the air intake temp sensor and coolant temp sensor to determine the length of time to run the GPs. If these arent hooked up or working, I *think* that the PCM defaults to a standard time length. Im not sure what wire in the harness controls the GP relay, because I still havent hooked mine up either. I was just going to look under the hood of a buddies PSD to see which wire it was. Once the right wire was found, a simple test with a test light would determine how long the PCM will keep the wire hot for. Some guys like having a switch instead of the PCM to control the relay, just so there is more control.

 

[MMcCallie]

My oil and water sensors didn't work through the PCM when the guys did the wiring. It has temporary mechanical gauges sitting on the console until i can try to fix it. Will have to check on the air intake sensor. Also have no tach yet.



I will definitely go with the Stancor relay, price is more reasonable than i was expecting for that many amps. Would it be a bad idea to run a jumper cable from a positive battery post to the posts on the grid heaters for a minute and try cranking? Just wondering if that could be a possible alternative to ether.

 

[FordCummins]

You could try jumping it, 12V is 12V, its a good way to test them. Let me know if you have any more thoughts.