Engine/Transmission (1998.5 - 2002) Grid heater

[SAndreasen]

What do I need to check to make sure my grid heater is operating ? 24 valve engine

Thanks Shaun

 

[Sticks]

There are two relays under the drivers side battery. Each one controls half the grid heater. Make sure the terminals are tight and clean. The two smaller terminals are the signal wires coming from the ECM to close the relay. The ECM turns on the intake air heaters when the temperature is below 50* (wait to start light will stay on for several seconds)



You can disconnect the black wire (the other is black with a tan tracer/stripe) and use jumper wires to manually close the relay and use a test light to verify that you are getting power at the output stud on the relay and or at the corresponding terminal at the grid heater.



Use a volt meter to check the resistance across the terminals on the grid heater (disconnect either the ground or hot legs). It's either going to be open, or less than 1 ohm resistance. If it's open, or greater than 1 ohm, then that coil is broken.



Your battery voltage will drop significantly when they are on. Each of the two coils pulls around 90 amps when on.

 

[SAndreasen]

Thanks a bunch for the reply my grid heater isn't working need to figure out why I'll check what u said and report back

 

[Mike B.]

What else isn't working? Does the wait to start light come on and does the lift pump prime when you first turn on the key? I'm asking because I had all three issues and a replacement ECM is what it took to make things right. The Lift pump not running for sec. or two as well as a long delay before the wait to start (and heater grid) to light are classic symptoms of a failing ECM. Hopefully I'm reading more into to this than there is.

Mike

 

[Mike B.]

You may also want to remove the intake horn just to make sure a PO didn't remove the heater grid, some folks do.

 

[SAndreasen]

The wait to start is working the pump is pumping 12 psi when I bump the key also getting 12 at 2000 rpm. Also I could hear the solenoid click under the hood this morning.

 

[Mike B.]

That's good but double check when everything is heat soaked, that's the only time mine ever had any issues. Chances are you're fine, most are.

 

[SAndreasen]

I pulled the horse trailer on a 2 hour trip Sunday and everything was working fine . I know the grid heater isn't working buy the way it starts when its cold .

 

[Sticks]

Check your voltages at both sides of the relay. IIRC there is a fuseable link for those rather than a standard fuse.

 

[SAndreasen]

Thanks for the replies I'll check things out and let ya know what I find

 

[SAndreasen]

I did a check on the power side of the grid heater and no continuity meter reads ol there is continuity on the ground terminals. So I checked the terminals on the 92 which I know the heater works and there is continuity on the power terminals

 

[Sticks]

Hard time understanding what exactly you checked.

I presume you disconnected the power wires to the grid heater when you checked continuity?

If you did and got OL - then your one or both of your grid heater coils is broken and needs replaced.

Also check the ground stud (not the eye terminal) to ground on the engine. If OL - remove, clean the corrosion and reinstall, repeat the test.

Check the power wires from the relay stud to the eye (while disconnected). If OL - remove, clean the corrosion and reinstall, repeat the test.

Is the base of your intake horn dark brown or severely discolored?

 

[SAndreasen]

The intake is dark brown and no I didn't disconnect any wires on either truck I just checked the terminals where the large power wires hook to the grid heater and got an ol on the 98 that the heater doesnt work and .5 on the 92 that the heater works

 

[Sticks]

Probably going to have to replace one or both of your relays. Sounds like one of them got stuck in the on position and burned it (grid heater) up. Hopefully it's just broken not missing any pieces. I'm willing to bet that you had battery/charging issues recently.

Not sure of the compatibility of the 92. I don't think that they did any changes to the intake design so it might work. Won't know until you try it.

 

[SAndreasen]

Probably going to have to replace one or both of your relays. Sounds like one of them got stuck in the on position and burned it (grid heater) up. Hopefully it's just broken not missing any pieces. I'm willing to bet that you had battery/charging issues recently.

Not sure of the compatibility of the 92. I don't think that they did any changes to the intake design so it might work. Won't know until you try it.

Thanks for the all your help and yes both batteries went bad the other day they were 8 years old though

 

[Sticks]

My stock batteries went 11 years.

Depends on how often you pop the hood, or would notice the color change if that was the cause. Those puppies draw 95 amps each. Real hard on the batteries and alternator with that much draw for an extended period. My money is that the grid heater relay is what sent your batteries over the edge, and consequently killed your grid heater.

 

[SAndreasen]

How do I check the relay? Won't I have a low voltage reading if the grid heater is stuck on ?

 

[SAndreasen]

I took the grid heater off the 92 and its almost identical to the one on the 98 I put it on and it did pre heat cycle and several post heat cycles and then stopped so I'm hoping its working right

 

[SAndreasen]

I left the truck unplugged and the hood open its 14 degrees I just went and checked the heater operation again wait to start light came on then went off trucked started better than it did before when it was 45 degrees turned the lights on and they would dim and voltage would drop then come back up indicating a post heat cycle then voltage stabilized after a few minutes so I think its working like it should

 

[JR]

At 14 degrees the grid heater operation will be much more obvious then at 45 degrees. Anything above the low 30s or so and I don't even give them a chance to cycle I simply start the truck. It starts just fine without them so why wait.
I'm not sure if you ever get on Cummins Forum but I saw a grid heater and both relays for sale in the classifieds for $50 bucks. That's a pretty good price I think. I've never priced the elements but I know the relays are up there.