Need HELP unhooking Grid Heaters 2003 Cummins Ram

[bobinyelm]

2003 Ram 3500 HO

I am far from home in the Pacific Northwest with a problem and need to disable the grid heaters at least temporarily. It is cold raining 24/7 so I am looking for the cleanest/quickest way to disable the heaters. When they activate they are disabling my external lift pump, so the engine quits. When warm (and the heaters are not activated, everything's fine).

I found reference to a fuse that controls power to BOTH grid heater relays (solenoids) but I don't know where it is located in my fusebox. (The coils are "hot" via this circuit and the PCM grounds the other side of the relay coils to activate the relays)

Can anyone help with a fuse location?

An alternative is removing the fusible link wire (that feeds the heater relays on the engine block) at the battery terminal, but I don't SEE a separate terminal connected to the left battery terminal that can be removed. The terminal has several wires molded into it that cannot be removed, however.

Any help to disable this circuit w/o having to climb into the engine compartment would be most appreciated.

Thanks-

 

[DonFitzwater]

So why don't you simply disconnect the power wire at the heater element? Either way you'll end up with a check engine light. You can also disconnect the wires from the solenoid that operates the grid heater. I think the relay is on the right side battery (passenger side).

 

[bobinyelm]

Thanks-

I just came in from disconnecting the power wire (fusible link wire) at the RIGHT side + battery terminal (I'd previously thought it was on the Left Side- DOH!!), and it started right up, with the Air Dog fuel pump sounding fine (rather than cutting out when the heaters cycled).

No more dimming dome and headlights as when the heaters turned on, either.

Because the heater wires AT the heater would be hot and hanging loose (even if I wrapped them with tape), I wanted to disconnect/disable the system where it seemed safer from short-circuits (rather than at the grid heater itself). Withe the hot end of the fusible link now disconnected, there are no hanging "hot" wires.

Just curious why my voltmeter shows about 14v after engine start for about 2 minutes, then pops up to 15.5v or so (indicated on the gauge anyway) after the engine's been running for that period.

I always thought it had something to do w/ the heater circuit (95 amp draw), but w/ the heaters disabled it still does it. Any idea?

Thanks for the suggestions,
Bob

 

[AH64ID]

The voltmeter isn't a real voltmeter and it reads whatever the ECM tells it to. The ECM is still telling it to drop to ~12V even thou the real voltage doesn't drop.

I remove my grid heater in the summers and the voltage still drops on days where the temp is below 66°. I have never seen a CEL from the disconnected heater thou.

 

[SnoKing]

So, why is this happening? Are your batteries weak? SNOKING

 

[Ozymandias]

The voltmeter isn't a real voltmeter and it reads whatever the ECM tells it to. The ECM is still telling it to drop to ~12V even thou the real voltage doesn't drop.

I remove my grid heater in the summers and the voltage still drops on days where the temp is below 66°. I have never seen a CEL from the disconnected heater thou.

It shows pretty acurat the voltage, i checked this with an external gauge for a longer time because i had concerns about the readings.
it doesnt shows the commanded value.

also it can show 15.2V or a little more, this is normal.

 

[Ozymandias]

but it is an interesting thing that you see a drop even with disconnected heater, that IS Funny.

 

[AH64ID]

but it is an interesting thing that you see a drop even with disconnected heater, that IS Funny.

Mine shows close after the grid heater cycle but not 100%.

Even with the grid heater sitting in the garage the voltage shows ~12V for the 2 minute operation, even when it's commanded off and the actual voltage is ~14. My dad's 06 bounces with the grid heater cycling thou. The ECM thinks the voltage will be low so it shows it low even if it isn't.

ECM driven gauges suck!!

 

[bobinyelm]

My batteries are new Interstates and very strong, actually.

I don't know WHY the lift pump runs badly w/ the grid heaters on, since yesterday I measured the voltage going to the pump at 14.38v unless the pump ground is questionable and somehow that's related. I replaced the pump control relay thinking maybe THAT was the problem, too. With the weather and few tools, I don't want to climb under to follow the ground.

Seems OK for now, though until I can really get into it I guess (I hope).

I wish they had left the stock lift pump in place, just bypassing it, so it could be re-connected.

The guy that installed it wrapped EVERYTHING with a mile of 3M"66" black tape so you can't see what goes where, unfortunately.

 

[bobinyelm]

Mine shows close after the grid heater cycle but not 100%.

Even with the grid heater sitting in the garage the voltage shows ~12V for the 2 minute operation, even when it's commanded off and the actual voltage is ~14. My dad's 06 bounces with the grid heater cycling thou. The ECM thinks the voltage will be low so it shows it low even if it isn't.

ECM driven gauges suck!!

Yes, I'd rather see the REAL voltage bounce with the lights dimming/brightening also.

 

[AH64ID]

Yes, I'd rather see the REAL voltage bounce with the lights dimming/brightening also.

And oil pressure...

 

[Ozymandias]

Wait a minute, the pump is fitted with a stand alone harness, why do you have to search for the ground?
For this problem is related to the cables, normally the OEM pump power only triggers the relay of the harness.
And this power source for sure doesn't cycle or worst shut off with the grid heater.

 

[bobinyelm]

Wait a minute, the pump is fitted with a stand alone harness, why do you have to search for the ground?
For this problem is related to the cables, normally the OEM pump power only triggers the relay of the harness.
And this power source for sure doesn't cycle or worst shut off with the grid heater.

I thought perhaps that the slightly reduced system voltage when the grids switched on was affecting the pump motor.

Now that I did disconnect the heaters, and the pump does the same thing for the first couple of minutes (sound of the pump motor fluctuates), maybe I have a dying motor. I changed the Air Dog pump relay a while back, and it "cured" this problem for about 5000mi, but it's doing it again (and another relay DIDN'T solve it this time).

 

[SnoKing]

When I was a field tech at NCR in the late 60's and 70's they taught us to fix the root cause and not a symptom down stream. Snoking

 

[AH64ID]

When I was a field tech at NCR in the late 60's and 70's they taught us to fix the root cause and not a symptom down stream. Snoking

Which is what it looks like the OP plans to do as he mentioned he needs a temporary fix since he is a long ways from home.

 

[AH64ID]

I thought perhaps that the slightly reduced system voltage when the grids switched on was affecting the pump motor.

Now that I did disconnect the heaters, and the pump does the same thing for the first couple of minutes (sound of the pump motor fluctuates), maybe I have a dying motor. I changed the Air Dog pump relay a while back, and it "cured" this problem for about 5000mi, but it's doing it again (and another relay DIDN'T solve it this time).

How old is the AD? They have had a run of bad pumps over the last few years. The issue is supposed to be fixed on the warranty motors so I would give them a call.

 

[bobinyelm]

When I was a field tech at NCR in the late 60's and 70's they taught us to fix the root cause and not a symptom down stream. Snoking

Of course, but when you are 1500mi from home, it's 40deg, raining hard, and blowing 40mph, I am not sure troubleshooting the whole problem under a shade-tree is a desired activity.

I just wanted to keep it running.

But if you have time to come over to Tenino, WA and help me do it right before Thursday when I have to leave, I'd welcome the help!

 

[AH64ID]

Of course, but when you are 1500mi from home, it's 40deg, raining hard, and blowing 40mph, I am not sure troubleshooting the whole problem under a shade-tree is a desired activity.

I just wanted to keep it running.

But if you have time to come over to Tenino, WA and help me do it right before Thursday when I have to leave, I'd welcome the help!

I thought you laid that out in the first post... :-laf

 

[bobinyelm]

How old is the AD? They have had a run of bad pumps over the last few years. The issue is supposed to be fixed on the warranty motors so I would give them a call.

You are correct, and in fact I have a new motor/pump assembly in the rear footwell of my truck, though if I can nurse it home, I won't have to lie in the mud dropping the old one and swapping out the motor and pump.

And, yes, I DID lay out the circumstance in my first post, but someone else in WA made a comment that it's better to FIX the problem than treat the symptom, with which I AGREE, when its "cost effective" in effort and ability. I fully intend to do it right when I can. Hopefully the old motor has 30 hours left in it.

 

[SnoKing]

You are correct, and in fact I have a new motor/pump assembly in the rear footwell of my truck, though if I can nurse it home, I won't have to lie in the mud dropping the old one and swapping out the motor and pump.

And, yes, I DID lay out the circumstance in my first post, but someone else in WA made a comment that it's better to FIX the problem than treat the symptom, with which I AGREE, when its "cost effective" in effort and ability. I fully intend to do it right when I can. Hopefully the old motor has 30 hours left in it.

If I had a thirty hour drive ahead and the parts in a foot well, I would be finding someone to put it on a hoist and let you install the new one or pay them under your supervision, as doing it half way up a mountain pass would not be a chance that I would want to take. Maybe there is a member in your current area that will provide a nice garage to work in? Post the details and ask!

I had a problem on the road back in the early 70 with an old 63 sub in the middle of no ware in the dead of winter. Colder than a witches ***** and wind blowing 40 MPH. Was just putting the distributor cap back on after inspecting when I noticed the condenser mounting screw was loose. Easy fix and I was lucky to have found it.

So my advice would be to do it right before heading out on the trip.

SNOKING