GPR Shunt

kawa · #1 (**permalink**) 11-05-2009, 12:25 PM

Does anybody have an extra GPR Shunt that I can Beg, Buy or Steal. I'm going to try to fashion the shunt onto the "Stancor 586-902" so that it will work properly on the Cali trucks. I'm a little reluctant to use the only one that I have as it is on my truck and it will need to be modified.

Orrrrrrr, tell me what exactly comprises a Shunt, can one be made from scratch? Is there something mystical, magical about it's construction?

Any input will be appreciated.

Rog

Neal 97 250 · #2 (**permalink**) 11-05-2009, 12:33 PM

Not shure what you mean by shunt???

Action4478 · #3 (**permalink**) 11-05-2009, 12:40 PM

Pic ...here....

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superduty4x4 · #4 (**permalink**) 11-05-2009, 12:46 PM

Rog, its just a bent up piece of steel. I'd head to the hardware store and buy some metal straps and fab away. I can get you a pic of mine here in a bit if you need.

pjwoolw · #5 (**permalink**) 11-05-2009, 07:38 PM

I was thinking along the same lines Chase. That shunt looks like stainless steel Rog. I think MustangMatt96GT purchased a new one some time back. I was going to take measurements but never got around to it.

kawa · #6 (**permalink**) 11-05-2009, 08:40 PM

Quote:

Originally Posted by pjwoolw

I was thinking along the same lines Chase. That shunt looks like stainless steel Rog. I think MustangMatt96GT purchased a new one some time back. I was going to take measurements but never got around to it.

Pete:
You have Mail

Rog

Hussler · #7 (**permalink**) 11-05-2009, 09:11 PM

Na, don't think so. The shunt is has to be a special allow or something. PCM has to know in advance what the voltage drop across the shunt is to determine correct current draw. Different materials would cause different voltage drops. It is a terrible design for those that have Cali rigs which seems to cause more issues than it was designed for.

But then again, I could be wrong ...

pjwoolw · #8 (**permalink**) 11-05-2009, 09:42 PM

All the descriptions of the shunt refer to it as a resistor. Still hunting for info.

The Motorcraft part number is DY840. $12.00 or so. I should have thunk about this a little more Rog or I would have sent one to ya. Not sure yet on that part number.

kawa · #9 (**permalink**) 11-06-2009, 12:28 AM

Quote:

Originally Posted by Hussler

Na, don't think so. The shunt is has to be a special allow or something. PCM has to know in advance what the voltage drop across the shunt is to determine correct current draw. Different materials would cause different voltage drops. It is a terrible design for those that have Cali rigs which seems to cause more issues than it was designed for.

But then again, I could be wrong ...

I'm with you you on this one Jim. And Pete, I think you are also right, that the "Shunt" is a resister of sorts, it's telling the PCM something. Just a piece of metal doesn't make sense to me. there is more to learn that's for sure.
Rog

MADVAN · #10 (**permalink**) 11-06-2009, 07:52 AM

Rog

The shunt is not a resistor. Its just a load splitter (current)
so the pcm can see left and right side of the gp's. If you have
to make a new bar be shure is can carry the load. Its in the 110amp
area. I made 1 using parts from an old electrical panel that had bolt in
type breakers. I used a branch ckt bar to fab the shunt. Another way
is to get some copper tubing and flatten it.
I have done both above with the use of penetrox for all the connections
and have not had any of the false codes you can get with the gp's self
check system.

Bill

kawa · #11 (**permalink**) 11-06-2009, 12:28 PM

[quote=MADVAN;8112966]Rog

The shunt is not a resistor. Its just a load splitter (current)
so the PCM can see left and right side of the GP's. If you have
to make a new bar be sure is can carry the load. Its in the 110amp
area. I made 1 using parts from an old electrical panel that had bolt in
type breakers. I used a branch ckt bar to fab the shunt. Another way
is to get some copper tubing and flatten it.
I have done both above with the use of penetrox for all the connections
and have not had any of the false codes you can get with the GP's self
check system.

Thanks Bill,
I was fairly sure that a "Shunt" was more than just "Ugly & Metal"
I too was thinking copper or brass.
Rog

barebackjake · #12 (**permalink**) 11-06-2009, 09:50 PM

with the shunt you put current across it and you will get a millivolt output, it is in a sense a resistor. there will be a millivolt drop across the material which increases with current so with the differnce in potential the pcm can determine the current in the system. if you were able to find out what the proper mv ranges are you could set it up for the proper output to fool the pcm.

kawa · #13 (**permalink**) 11-07-2009, 01:19 AM

UP DATE: (I hope)

Spoke with a Ford "Guru" Vic at a Ford dealership today in Grants Pass, OR. I was very impressed with his knowledge particularly after I showed him Fords article #98-15-1 indicating that DTC's P1391, P1393, P1395 and/or P1396 can be stored in memory in the PCM. (Cali Only).
Ford lists a whole slew of remedies to preform to correct these codes and if they fail to have the PCM re-flashed. Tried this and Ford dealer refused with a whole bunch of crappy reasons, charged me $95.00, kissed me & shoved me out the door.

Vic told me that he could re-flash the PCM but would more than likely the codes would return. Then he asked if I had tried changing the "SHUNT"? No one had ever asked or indicated that a Shunt could go bad. I ordered one.

I realize that the above has very little to do with the original question re adding a "Shunt" to Stancore but it is a hell of a great piece of news for the Cali owners that may have these constant codes.

I'll try the new shunt on both the OEM relay as well as the Stancore and let ya all know if it burns to the ground.

Rog

joe_13894 · #14 (**permalink**) 11-07-2009, 02:04 AM

A shunt is a resistor. A very low value one, but a calibrated value. Its purpose is to produce a known, small voltage drop proportional to the current draw.

Shunts are usually made out of constantan or maganin. Constantan looks like nickel and maganin looks like a grayish bronze. Both are alloys that have very little change in resistance with temperature.

If you use iron, you may get the resistance right at one temperature, but it'll be way off when warm because iron changes resistance quite a bit with temp.

At $12, buy the right part.

MADVAN · #15 (**permalink**) 11-07-2009, 09:16 AM

The gp shunt system is not a bypass resistive type shunt.
Its more a buss bar than a shunt in its application.
Its a diverter (splitter) type shunt. This is done to split the load
in 1/2 (L/R gp's), so the pcm can read the load balance. The pcm
has predetermined software of min/max with imbalance L/R.
It can sense 1 bad gp up to all 8. It cannot tell you exactly which gp, just
L/R side. (bank 1 or 2).

A ohm test of a good shunt shows infinity.
False pcm codes will/can come from resistance of the shunt itself.
This is from age/heat cycles.

Rog
Use penetrox on all the gp relay connections not die grease.
The shunt gets wicked hot and connections are not made
of the same materials (metals).

Bill