Grid Heaters Not Working | 1st Gen Cummins

*NOTE...my testing procedure is wrong in this video and I'm planning on making an updated video going through the process of diagnosing bad grid heaters. I should have tested for resistance through all my leads to ensure continuity and then tested the ground circuit with a multi meter to ensure all is functional*
Today I run you through the grid heater setup on a 1st gen cummins. They are wired very simply and are quite straight forward to diagnose if you are having problems with them. They are very robust and chances are if they are not working it's a small issue like a bad ground as shown. The only other things to check are the fusible links, relays, wiring, grids themselves, and then the ground.
Stay tuned for more videos!
Tyler,
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[@DennisHosangJr]

Thanks for the video... It helps me troubleshoot. I heard a whining that just never turned off and I popped the hood and saw a wire on the positive side just lightly smoking and it was very very hot to the touch... at this moment assuming the whining noise is the grid heater but I don't think the relay is disengaging. Disconnected the battery to stop the smoking and reconnected and no smoke or whining so anyhow long way of saying this is the rabbit hole I'm going to go down at the moment. Someone messed all the wiring up so stumbled on your video trying to identify all the wires and what they are for so I can fix it correctly so thanks again

[@ronsre-creations5289]

Great step by step tutorial. Another 1 for the sticky notes. Thumbs Up !

[@superkittybtc]

great stuff as usual could you plz show us how you got rid of the rat's nest of a fire hazard? love how what you did with the fuse panel under the hood

[@OvensGarage]

I'll be doing an aux fuse block install in Ol' Blue within the next week or two hopefully. I'll video it!

[@superkittybtc]

@@OvensGarage oh that would be insane !! 😳 that would help the community 1000x

[@pixel288]

For what it is worth, that .27 volts you were seeing is the voltage drop across the relay itself. It’s the resistance of the contacts themselves.

[@FirstGendodgegarage]

Do the relays need to be ground on the fender ?

[@usewhatyouhave6975]

Awesome video. Thanks

[@OvensGarage]

Thanks for watching!

[@paulurban7778]

I’m still having issues with my grid heaters even with new relays, my abs light and brake lights cycle, my wait to light comes on but the water in fuel light doesn’t come on at all, is that a concern?

[@OvensGarage]

Maybe the bulb is out on the water in fuel. The PCM on these trucks has a built in feature to turn on all the lights on the message center as a bulb check when you cycle the key. If one isn't coming on it's either the bulb or a connection to the bulb on the back of the message center. I've seen some pins come loose on them so check that.

[@mementomori2353]

Could a short in a ground or directly to your grid heaters cause the truck to not start? Mine looked like they burned up the last time I tried to fire up the truck.

[@franklogan494]

Great Video Tyler!! What should the charging voltage be, when you are driving? I have a meter coming out of my cigarette lighter for my accessories and it is showing 14.5 to 14.7 volts, is that to high? Thank you.

[@OvensGarage]

That's about normal. My dash gauge reads about 14v when charging.

[@franklogan494]

@@OvensGarage Thank you!

[@miniatures1]

Ovens Garage HI I am having trouble with my 1990 cummins when I turn my key to the wait to start nether my wait to start light or my water in fuel light comes on also my relays and my grid heater don't make a sound. It acts like it is already warmed up but when you start it when the engine is cold it runs ruff until it warms up like its not working at all any thoughts?

[@OvensGarage]

Those are classic symptoms of a failing or failed PCM. Check out my other videos on PCM repair to see how I fixed mine. It is quite simple and a very common problem with our old computers. There are three main capacitors on the PCB that need to be replaced and this will fix your problem.

[@miniatures1]

@@OvensGarage Unfortunately that is not my problem the earlier nonintercooled trucks have no pcm they have a electronic control module that acts as a air heater controller.

[@cadeamber2356]

I’m having an issue with my grid heater but it’s way more complicated than yours, I have a 90 model so it doesn’t have a pcm either, so if I would get any insight that would be great.

[@OvensGarage]

I would start by taking a look at your factory wiring diagrams if you have them! How are they wired.

[@cadeamber2356]

@@OvensGarage can I send you a video on Instagram explaining it? We thought we had it figured out snd bought a new part but that didn’t fix it.

[@OvensGarage]

@@cadeamber2356 sure!

[@loganford3971]

What are symptoms of a bad PCM

[@OvensGarage]

Go and check out my pcm video I have one where I describe what to look for in a pcm that's going bad

[@loganford3971]

@@OvensGarage do you have a Facebook or a way for me to get in touch with you ?

[@OvensGarage]

@@loganford3971 yes you can email me contact info in description of video

[@billyjonkman2244]

Testing from the positive post of the battery to the incoming side of the relay should not give you any voltage reading. That would be the same as sticking both leads on the positive post... zero potential as both are on 12+. You would need to use the negative terminal for testing that. Are you sure that you had the correct sides of the relays identified? Judging by those voltage readings you had the relays terminals mixed up. I think first reading you took of around 10V was reading through the actually grid heaters to ground. They are resistive loads and I would assume you would see a ground through them. That loose ground was probably all that was wrong as when a high amp load is put through a bad ground it will often cut out (think of a corroded negative on your battery - accessores work but when you go to start it cuts out) Long winded comment but just trying to clear that up as your voltage readings confused me.

[@OvensGarage]

You know what you are probably right! I totally didn't even think of that when I was diagnosing the issue. Duh. Positive on positive shouldn't give me voltage at all..lol. maybe I was thinking I was measuring resistance. I'll probably end up re doing the video. Thanks for the tip

[@billyjonkman2244]

@@OvensGarage ya man, just my observations, hard to say over a video as I've never touch my grid heater before. Appreciate the videos, not many people doing good quality videos on our trucks, always enjoy watching you and decent garage 👍

[@roughcutsgarage]

You should hook a turbo up to your cameraman. I can hear he moves a lot of air lol.

[@OvensGarage]

Lol 😆

[@Off-GridLife54]

Should have black/negative to ground and red to solenoid output

[@kimmiles3476]

🎉🎉🎉🎉🎉🎉🎉