Engine/Transmission (1994 - 1998) Heater Grids shorted together? Short cycling?

[Fordiesel69]

Maybe I am testing it wrong, but on the front of the grid heater there are 2 nuts for the power wires. I put one test lead on one nut, and then the other test lead to one of the nuts on the back side, but it make no difference which one on the back, it show shows continuety on both. So does this mean that when one element tries to energize the other one does also? Is this how it should be? I thought the PCM could turn on just one element if it wanted?



Also where is the IAT sensor located?

 

[Fordiesel69]

I can also test the two power nuts together and they show continuety. Should they?

 

[JFaughn]

I haven't looked , haven't had a problem yet .
But I would think that both of the connections are positive from relays , the other end of the grid heater is connected to intake for ground [ no ground wires , like anything most on the eng , starter & alt do not have a ground , the use there mounting surfaces to make ground .
So to test , resistance from power connection of grid heater to manifold .

 

[Fordiesel69]

Ok, I see what you mean with a common ground. But why do I have continuety between both power posts on the front? That would mean both coils energize together, is that supposed to be this way?

 

[Joe G.]

The heater grids draw 90 amps. That will look like a short on an ohm meter.

 

[B.G. Smith]

Ok, I see what you mean with a common ground. But why do I have continuety between both power posts on the front? That would mean both coils energize together, is that supposed to be this way?

The ground side of both heater elements are tied together so you will see resistance between the power posts, you are reading through both heater elements. Both heaters energize at the same time but through two seperat relays. bg

 

[Fordiesel69]

The ground side of both heater elements are tied together so you will see resistance between the power posts, you are reading through both heater elements. Both heaters energize at the same time but through two seperat relays. bg

The problem I am having is that if I watch the volt meter and lights for that matter, the first few draws, pull the gauge down to the 9v position and the lights really dim, then the rest of the cycles only go down to the 12v section and the lights don't really dim as much but you can still clearly tell they are cycling. I actually thought this was how the PCM regulated it, are you saying they are both supposed to work together? If so then I may have a problem with one of my relays.



Where can I get replacement relays?

 

[B.G. Smith]

Sounds about normal to me. I think what is happening is after the heaters come on the first time the Pcm sees the low voltage, the alternator kicks into high output and charges the batteries a little while the heaters are cycled off, also the grid resistance will be higher and draw less current since they are still warm from the first cycle. bg

 

[ata]

I think what you are seeing is, When you first start the engine the GRID heaters come on and cycle and draw a lot of voltage then shut off. But the fuel heater keeps cycling. Which draws less voltage. Atleast that's what I found on my 97.