I had trouble earlier this year with my cluster. You've replaced the printed circuit which is awesome. The plug that goes INTO that printed circuit has contacts that are sort of spring loaded. I needed to pry all of my contacts out a bit to bring their spring back, allowing them to make good contact with the printed circuit once it was pushed in. I also cleaned all the contacts on the plug w a piece of Emory cloth rolled to a fine point. It was tedious, but solved every dash (and charging) issue I had.

 

Not trying to sound mean, but you should start your own thread in the 1973/79 Dentside forum. Ford never sold an assembly, just separate parts. In looking online for a picture to show you this, I found a bunch of used ones.

 

I have the gauges...oil pressure, ammeter, water temp. Bought the printed circuit for the 1970 with gauges. Lights on the dash work and it looks like the ammeter works. It's showing around 12 volts and moves slightly when I switch the key or turn headlights on.

 

I'll check those to see if I can pry them out a little if they seem compresses. I did notice markings on the printed circuit on each contact where the plug attaches, so it looks like all contacts are being touched.

When I have the key on acc.I tested for power at each tab in the wiring harness connector. Only about half show they are getting power. Not sure if all of them should be when the key is on?

 

Looked at it a little more last night. I replaced the voltage stabilizer on the back of the cluster just in case, but no change. As I mentioned above, I checked each contact point in the cluster wire harness connector and getting power to about half of the contacts when the key is on. Most of those contacts lead to the gauges on the printed circuit.

Here is what I have so far:
-Tested for power at the back of the switch when key is on. Two wires didn't have power, a light purple and a red/yellow (ish).
- The fuse box is a 5 fuse...no power at either terminal end for the fuse that runs instrument cluster. On the back of the fuse box it looks like a blue/red and a black/red run to that fuse. Also looks like it's supposed to connect with the fuse next to it based on the diagram. Noticed one end of the fuse on the back of the panel for the cluster just barely touches the fuse connector next to it. Based on the diagram, maybe it's supposed to?
- Some wires at the base of the ignition switch wiring harness are mangled. I just ordered a new harness and switch from CJ Pony. I'm leaning towards either some faulty wiring at the wiring harness has finally given up, or the switch has.

 

Update...I replaced the ignition switch and the wiring harness to the switch, but still no change. I'm completely out of ideas because I think I've ended up replacing just about everything involved with getting the dash gauges to work again. The amp gauge still works, but still no go on fuel, oil pressure, and temp gauges. Here's a recap of what I've done:

• replaced instrument cluster printed circuit
• replaced voltage regulator on back of instrument cluster
• replaced ignition switch & wiring harness
• pulled out each of the connectors a little on the instrument cluster wiring harness to make sure they're making good contact with printed circuit
• checked power to wire 19A (blue/red) that runs from light switch to fuse box to cluster wiring harness and getting power. Lights work on dash

Any ideas what I'm missing? All of the gauges used to work, then around the same time I took out the cluster to put in my dash pad, they stopped working. The printed circuit where the harness plugs in was crusty and shot, so that needed to be changed. I get the feeling there's one wire (maybe a ground?) that came unhooked that is in the loop of the cluster wiring harness, but not at any of the areas I've looked at. When the cluster is plugged in, dash lights on, and ignition on, should there be voltage running through each pin on the cluster wiring harness?

Also, anyone know what these represent in the wiring diagram? It looks like 19A comes out of the cluster harness as 19B, then dead ends as 19C?

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The only thing that comes to mind might be the headlight switch..and it's dimmer mechanism. Maybe that isn't working peoperly...
although, I think that would only effect illumination, not operation.

 

This is a shot from when I had my cluster disassembled. If you look next to the gauges, there are the rectangular brackets and nuts that attach each gauge to the metal housing of the cluster. Maybe they get their ground through that connection and those points are corroded?

 

I seem to remember someone mentioning grounding each sender wire at the sender.
Did you do that?

 

And getting back to the earlier discussion, remember that the Blue with red stripe wire from the headlight switch should, in theory, have absolutely nothing to do with the function of the gauges.
It is strictly the instrument cluster illumination circuit and that’s all it does.

Now I can’t say that that remains the same if the printed circuit part was manufactured wrong and maybe messed up some of the functions. But I think you would see that in other failures to work as well.
Being just the gauges would seem to rule that out.

I do seem to remember someone saying that your year printed circuit board was a one year only unit? I’ll have to go back and check if that was this discussion or another.
I mention this because 1-year only stuff is notorious in the aftermarket for not being correct.
The companies that make these often mix up wiring diagrams, or don’t get the right one in the first place and think that one printed circuit is the same as another.
But here again, that possibility doesn’t seem to play out in your case, with other malfunctions.

But at least report back on what grounding out the sending unit wires does when you turn on the key. You can do one at a time, or all three and see what happens.

You certainly could have lost a ground, but the gauges themselves don’t ground directly for their function. The only ground running to the gauge itself is for the lightbulb.
The inner workings of the instruments are grounded through the sending units. Basically they are variable grounds to make the needles move a given amount.
I also don’t remember what you said about IVR output. I think you said you had battery voltage going into the regulator, but I don’t remember what you said about coming out.
Were you able to check that?

 

QUOT
That IVR regulator is what I also replaced. I think you're correct about the 1970 printed circuit being the only year. I bought one and gauges didn't work, so returned it and bought a different brand, thinking the first was a bad aftermarket part.

I'm not sure about how the variable ground works on the sending units if those 3 gauges. Does at least one of the wires in the cluster wiring harness run to ground for a gauge? I need to check the nuts and washers on the back of the cluster again. Don't think that's an issue because it's pretty straight forward

 

Don't overthink this. It is basic electrical theory. The gauge readings are based on resistance. You take off the sending unit lead, momentarily ground the lead with the key on, and if there is the 5 volts going to the gauge sending unit, it will have almost no resistance in the circuit and cause the gauge needle to peg to the max. Quick and easy way to see if the gauges can work.
'For panel info:
https://www.fordification.com/tech/67-72ID_01.htm

 

Had a chance to dig into this more this morning, and got nowhere. I understand the 1970 wiring diagram a lot better and was able to test for power or resistance at several points. Here is how I think the diagram reads:

• Power from ignition switch (wire 977) goes thru dual brake warming switch (the pressure differential valve under cab), to the brake warning light on lower left dash, then to wiring harness for dash cluster (wire 640)
• Into the printed circuit, it runs to oil pressure gauge, thru CV regulator, on to fuel and temp gauges, then out to wiring harness (wires 286 & 39)
• 286 goes to fuel sending unit and 39 goes to temp sensor.

I replaced the bulb on the brake warning light and that lights up. Then I put the multimeter on the CV regulator and I'm getting a negative ohm reading...bounced around but about -12 ohms. Have no idea if that is correct. I bought a new regulator, but doesn't make a difference.

Then I tried the suggestion from RichS2659 to ground the lead going to both fuel and water temp sending units with power on. No movement in the gauges. Need some help here...I don't know what it means when the gauges don't work after grounding. Any ideas? I'm stumped!

 

The #977 wire is not a powered wire from the ignition switch. It's a temporary ground wire for testing the bulb each time the key is turned to START.
If you note the point it connects to the switch in the diagram, it's listed as the Prove-Out position. That's the traditional (pre-computer) lamp test. The ignition switch grounds it to the dash when the key is turned to START.
Then the lamp goes back to dormant when the key is released.
Power for the lamp probably comes in from the #932 wire from the switch. That could be a common wire with the instrument cluster, but I can't see it all in the diagram especially with some of the corners cut off and on the smaller screen (that's a "my poor eyes" issue, not yours!) so not sure I'm following all the circuits correctly.
But I think that's correct.

Regarding the cluster regulator, you can't really measure ohms (or at least it takes a specialized method) and you probably would even have trouble measuring voltage using a digital volt meter. With an old analog meter with a needle you can see the needle pulse regularly between about 4v and 8v or so, averaging out to somewhere between 5 and 6 volts if I remember.
It's an electro-mechanical thermally compensating regulator. Only with a modern electronic version will you see a steady voltage output.
So you may have replaced it unnecessarily, but then again it's still hard to say.

Oh, and the diagram we're using here is for the alternator indicator lamp type. Didn't you say earlier you had an ammeter? Sorry if I'm remembering that incorrectly. I'm going to go re-read it, but with so many interruptions in my daily life, I never seem to be able to do anything in just one sitting!

It could mean, as usual, multiple things.
1. It could indicate that the gauges are not receiving the power from the regulator.
2. It could indicate a bad connection between each gauge and it's sending unit.
Those could be bad wires, bad connections, bad grounding method, or bad components still. It's not unheard of (or even unusual anymore) to get several bad ICVR units in a row. The instance of bad parts right out of the box is a rampant issue at the moment. So you can't just replace parts and assume they're helping solve the problem anymore.

Just to help me out, refresh my memory about whether you have the battery charge indicator lamp, or the ammeter.
It might be the case that both types use the same wiring at some points, but it would be standard practice by Ford if connection points in the cluster connector do not match between one type and the other.

Thanks!

Paul

 

With your VOM and a long piece of wire, check the continuity of #39 and #286 from the main 12-pin plug through the 3-pin plug to the wire plug end. Also, does your oil pressure gauge work also? You can also ground that lead to metal at the sensor end of the plug to check for ICVR operation. If the gauge pegs, the ICVR is working.