If the gauges work good on the bench, particularly with applying 12V or so to the IVR, then you should be good to go.
Your 14 ohm resistance from gauge post to housing may be due to the path through the IVR, if you measured it with the old-style IVR. I believe without power, the IVRās output is grounded (the device switches from ground to 12V, giving an average of 5-6V). If you measured with an electronic version, then I am not sure whether that ground path is valid or not.
I measured the resistance on 2 electromechanical units and one solid state IVR and got the following:
Original IVR: 0.4 ohms between input and output
72 ohms between input and case (ground)
72 ohms between output and case
Holly electromechanical IVR: 2 ohms between input and output
56 ohms between output to case (ground)
59 ohms between input to case
Solid state IVR: 497 Kohms between input and output
4 Kohms between output and case (ground)
381 Kohms between input and case
Well the saga continues. Retested the fuel, temp and oil pressure gauges on the bench, and all are working fine. Installed new blue diffusers while the cluster was out, and put everything back together. Bench tested the LED lights, and all good. Installed the cluster one more time, and started the car. Thought it was all good when the temp gauge didnāt go to max as before, but now the temp and oil gauges wonāt move at all. Fuel sender float needs replacing, so no reading there, but I know the gauge is good. I couldnāt find any shorts on the leads to the oil and temp sensors. I think itās still an issue with the repro harness connector and repro circuit board. Connector is well seated and all circuit board tabs appear to line up with the brass connector pins. Any ideas on what to try or test next guys? I thought I could fix just about anything, but this one has me stumped.
How did you test the gauges on the bench? Did you apply power to the CVR and then ground the output of the gauges to see them peg? Or did you simply determine a 14 ohm resistance across the posts?
Again, Iāll ask you to determine resistance between any of the gauge posts to the chassis ground: if you see 0-1 ohm or 14 ohm readings, one of the gauge posts has shorted to the case.
Each gauge was tested on the bench with the IVR and the Ford gauge tester so I could vary the resistance. Mounted in the cluster the gas, fuel and oil gauges measure around 14 ohms from the voltage input side to cluster ground.
Yeah, I still donāt like that 14 ohms from voltage input to cluster ground. That indicates that one of those gauge output sides are grounded, and since they are all tied together with the voltage input from the IVR, all of the gauges will be grounded and thus not show any reading.
Gauges not reading anything problem solved. The snap on the IVR input (12v) had come loose. Finally at last Iām getting normal gauge readings on the oil and temp gauges (fuel float still needs to be replaced). I still believe all the issues with gauges and cluster lights are related to the contact points between the cluster harness connector and the repro circuit board. The repro white harness connector tabs are a lot stiffer than the original connector and more difficult to seat properly (especially if you have big hands and canāt quite squeeze it properly). I had to use both hands. The repro circuit board is also a thicker material and if the connector pins are not all lined up height wise it might cause neighboring pins to not make full contact. If thereās ever a next time, Iāll order used original parts!
As for the resistance values I got the following measurements:
OIL TEMP FUEL
Across both gauge posts 13-14 ohms 13-14 ohms 13-14 ohms
Either gauge stub to cluster ground 4K ohms 4K ohms 4K ohms
Left gauge stud to circuit board pin 13 ohms 13 ohms 13 ohms
Right gauge stud to circuit board pin <1 ohm <1 ohm <1 ohm
Left gauge stud to to IVR output <1 ohm <1 ohm <1 ohm
Right gauge stud to IVR input 13 ohms 13 ohms 13 ohms
(Left/Right when viewed from the back of the instrument cluster)
thanks for all the comments and suggestions. Now on to the next project to replacing the fuel tank and sender float.
Have Bill B calibrate the fuel sender, that way it will be accurate.