AC voltage to speedo

[Moespeeds]

If you suspect that there's a crossing of the RPM feed somewhere, how 'bout simply disconnecting the RPM feed sonewhere down the line, preferably as close to the source of the RPM feed, and see if that affects the MPH reading.

That's what I'm suggesting, but since changing plug wires is easy I say try BDB's suggestion first. The bottom line is that especially with electrical problems it's important to tackle it in an organized and logical manner. Make a list of possible problems, ordered by how hard they are to troubleshoot, and isolate the problem. Check them off one at a time. So far I'd say try those plug wires first.

Next, snip the RPM lead down at the IGN. If it goes away then you know it's bleeding from the RPMs somewhere. First try jumping over the PDM to see if it's in there. If it doesn't go away then you're pretty screwed and don't have much choice but to go direct from the speedo to the sensor, or rip every wire out and go over them with a microscope.

 

[Moespeeds]

Have you checked that wire for DC voltage? Have you tested it with another multimeter to make sure the one you're using isn't bad?

 

[moesterman]

Have you checked that wire for DC voltage? Have you tested it with another multimeter to make sure the one you're using isn't bad?

Yep, it is a newer Fluke and I have test it. I will be checking as much as I can tonight....if work leaves me alone. I did call BDPP and Dave agreed to fabricate me a circuit to run externally to by-pass the harness if I need it. At least I can check teh speedo circuit w/o cutting more wires. Thanks again, Al

 

[BigDogBro1]

Correct me if I am mistaken, but isn't the rpm feed signal DC? The only AC source signal I am experiencing would be from the ignition I am assuming. I did change plugs and considered new wires but I find it hard to believe that the interference from the plug wires could be causing the 7volt AC reading on the sensor wire I am experiencing. I plan on checking the resistance on the sensor wire tonight and go from there.
As always, any ideas/thoughts are appreciated. Al

DID YOU USE RESISTOR TYPE SPARK PLUGS?

I think in the service manual it mentions that you need to use resistor type spark plugs or it can cause electronics operation issues.

 

[moesterman]

DID YOU USE RESISTOR TYPE SPARK PLUGS?

I think in the service manual it mentions that you need to use resistor type spark plugs or it can cause electronics operation issues.

Yes I did, that is why I changed them to be sure. The wires are the original 8.8 RF Suppression as well.

 

[Fibersnake]

The PDM is Big Dog Performance Parts retrofit for the old EHC. It is a replacement systems that allows one to change out the EHC and replace it with a new wiring harness, hand control interface and electronic module that uses relays and fuses to help protect the circuits.

Fairly new and is the same that was put on the last year models before BDM went under.

Still being sorted out of how good or bad it is. Moesterman has been dealing with a few electrical demons on his install.

I have a PDM in an so far no issues and do have the Dakota Digital Speedometer in also and running with no issues. That said there is only a few PDM out compared to the original EHC or even many that have installed Wire Plus, so long terms results are still being determined along with any common issues. So far Moesterman seems to have had the biggest issues, so could be a fluke or the initial appearance of flaws with the PDM.

At this point, I am happy with mine and still have faith, time and miles will tell if it holds up or if my next route will be as Moe suggest and go old skool and simple wiring.

 

[moesterman]

The PDM is Big Dog Performance Parts retrofit for the old EHC. It is a replacement systems that allows one to change out the EHC and replace it with a new wiring harness, hand control interface and electronic module that uses relays and fuses to help protect the circuits.

Fairly new and is the same that was put on the last year models before BDM went under.

Still being sorted out of how good or bad it is. Moesterman has been dealing with a few electrical demons on his install.

I have a PDM in an so far no issues and do have the Dakota Digital Speedometer in also and running with no issues. That said there is only a few PDM out compared to the original EHC or even many that have installed Wire Plus, so long terms results are still being determined along with any common issues. So far Moesterman seems to have had the biggest issues, so could be a fluke or the initial appearance of flaws with the PDM.

At this point, I am happy with mine and still have faith, time and miles will tell if it holds up or if my next route will be as Moe suggest and go old skool and simple wiring.

Well said Fiber. Even with the couple of issues I had (one pending) I have no regrets. Everone here as well as David at BDPP has been great in offering helpful insight. With the couple of glitches I had, now resolved I am one click away from buttoning this thing up. With that said, if you have been following this saga I am asking your opinion. I believe I have the speedo issue isolated and it is the speed sensor. I went back and checked the resistance in the sensor circuit in the harness as well as the power and ground. I then disconnected the speedo connector at the sensor and tested the the connector at the bucket at increased rmp's where there was no interference indicated. Logic suggest to me with this test it is isolated to the sensor--make sence? Al