Grid Heater Short

[AGPTurbo]

Hi guys, 

got the new grid heater battery jumper wire set I had ordered.  I put it on, tried it and fried it in 5 seconds- bye bye $40. Anyway, I just followed the troubleshooting instructions here after this disaster:

 

 http://dodgeram.org/tech/dsl/troubleshooting/Maniford_htr.htm

 

I have .1 or 0 Ohms (depending on the multimeter setting) across the heater grid terminals as stated in the 2002 instructions. But it seems like you wouldn't want 0 if going from the grid terminals to ground as that would in indicate a direct short to ground.

 

If I jump the grid straight to the battery its like a welder. Anyone have any issues with this before? I took the intake horn off just to check if something was sitting on the grid and it's clear.  Im not sure what could be grounding out. I also checked the heavy relay to grid wires and they are fine.  

I'm out of ideas and its 10F today and high of 1 and 3 F this week.

 

Thanks

 

[MnTom]

First of all is it one or both? If it is one then I would look real close at the insulating bushing where the stud comes out. If it is both then I would pull the intake horn and go from there, but remember, they do pull about 90 or so amps each and a lot of welding is done at lower amperage.

[AGPTurbo]

It melted the new wire in 3 seconds, so its getting way too much power. Hard to say if one or both because I get the same readings.  Are the bushings a problem?

[MnTom]

It melted the new wire in 3 seconds, so its getting way too much power. Hard to say if one or both because I get the same readings.  Are the bushings a problem?

I have not heard of many problems with the bushings. Something else you can do is pull the heater elements out to look at things better too.

edit: I found a video that shows the grids pull about 75Amps MAX. http://www.youtube.com/watch?v=LQONNwYr2ks

Edited January 26, 2014 by MnTom

[AGPTurbo]

I just pulled the relay set and checked them, No shorts or visible arc damage to speak of.  I put 12v to each side and they opened and closed normally.  I guess it has to be the heater itself- there is no other possibility I can see. I do see a NAPA part # CRB265000 for $161 and a mopar Part # 5086720AC for $130 from dodgepart.net (Berry Dodge, TX). Guess I'll order one up unless someone has another idea. 

AP

[MnTom]

Before you order one up take a bit of time and examine your heaters. They are really simple in design and about the only place I can think of is either the stud(s) are shorted or MAYBE there is something shorting the grid when it is put together. I have not ever heard of anyone needing to replace the grids.

[AGPTurbo]

Thanks MnTom

I'm going to check it again, The new fusible link burned in seconds , all wires check out, no direct ground paths. Only thing I can figure is the heater itself. 

Edited January 26, 2014 by AGPTurbo

[AGPTurbo]

Ok, Just for S's & G's, I pulled the air horn again, and took some high quality jumper cables and hooked them direct- battery to grid heater.  It never glowed, just made my jumper cables smoke lol.  I guess this thing i shorted internally.  I'll post the results of the NAPA trip tomorrow.

AP

Edited January 27, 2014 by AGPTurbo

[MnTom]

Again, they are so simple that about the only thing it could be is the insulating bushing(s) broken.Pull the other nut and check them.

[Yankneck696]

If the relay was not energized, & no shorts in the wiring, it has to be the stud. Is it 1 or both that do it?

I would see no problem putting used grids in & you can get them from southerners that think that they are losing massive amounts of airflow to them.

 

Ed

[AGPTurbo]

Got the new grid today from Bridgeway Cummins in Pittsburgh.  Cummins # 3969987 $99.55, (great price) Also 2 metal style intake gaskets PN 3969988 , 4.42 ea. I couldn't get a replacement from Rock Auto under 115 plus shipping. Swapped out, works perfect.  The old one had both grids hard shorted. I disassembled and all seemed normal, tested on the ground with jumper cables, did the same thing, hello scrap pile!.  For the $99, I wouldn't waste my time with used junk, especially since this one lasted 100K. Also, I tested the old vs. new with a multimeter- old read 0 ohms, new one reads 3-5 in case anyone ever gets in a similar jam. 

Thanks for the replies.

AP

[MnTom]

Glad you got it fixed! Plus it was a simple fix!!