I cant do this step. The gas gauge was only pegged while one of the mystery wires was grounded. Gas gauge reads empty now reguardless if the sending unit is hooked up.

 

This isn't making sense. One explanation might be this mystery cluster you installed. Did this cluster come from the exact same year and application as the original?

If you remove the cluster and look at the cluster connector coming from the TRUCK, each terminal should be numbered. If the truck has an ALT and OIL light, the wire going to pin 1 should be solid BLACK. If the truck has an oil pressure gauge and ammeter, it will be pin 9. This is not to be confused with the terminal that has a BLACK with GREEN stripe and solid BLACK wire bundled together (pin 6 for lights, pin 14 for gauges). Pin 1 or 9.

Pin 1 or 9 are cluster ground. Is the resistance between that terminal and bare metal behind the dash also under an ohm?

 

Dont think its the same year clustet. My original had seat belt, alt and oil pressure light. New one has brake, oil pressure and high beam.

I will check the connector later today.
Pin 6 the black wire is cut, the black with green stripe looks intact.

 

This is the first time i have read this thread....i read it all...

And i have decided, that i am going to punch a baby in the face everytime instructions are not followed or any deviation from testing.

You're welcome, just trying to do my part to help.

 

Pin 1 is solid black and under an ohm.
Pin 9 is solid red.

The cluster that came in the truck sais D6UF-10894-BA P-2. Lights = seatbelt, oil, alt and brake.

The one I installed sais D3TF-10894-BA 2-P. Lights =brake, oil, alt, hi beam.

 

OK, all bets are off with this new cluster. This is why going off and doing your own thing throws a wrench in electrical troubleshooting. Refer to Jklnhyd's comment.

Four pages is where I throw in the towel. Please take your truck to an auto electric shop. I'm sorry, there are too many variables here for me to effectively help you troubleshoot over the internet. This is the kind of thing that needs to be sorted out in person. I tried, but there's only so much that can be sorted out remotely.

 

I can put the old cluster back in but it has the same symptoms.

 

You're not getting my point. Please refer to one of your earlier posts:

If I catalog all of the symptoms you've described, you've said cluster A had problem X, then cluster B had problem Y, but in your last post, you're claiming cluster A actually has problem Y too. So now, again, I have to ask you what changed, why is this different than what you said last, and on, and on, and on.

Do you see what I mean? I can't keep doing that. I can't keep trying to keep a log of what you've described, only to have to ask you to clarify when you chime in later with something else that contradicts something you described earlier. I've done it several times already out of courtesy and it just keeps happening. We have reached the point of diminishing returns, where the problem continues to diverge instead of converge.

I want nothing more than to help people solve their problems, but there is a limit to how much of my personal time I can donate for free over the web. My honest advice to you is to take it to an auto electrician. Not because I think there's any sort of black magic with your truck, but because there are too many variables added, and the mystery wires are something that need to get looked at in person. The person doing the work needs to access the truck directly and not have you as the middle man like we're forced to over the internet.

 

Cluster A the fuel gauge worked. The dummy lights worked. Dash illumination did not work. When 1 mystey wire was grounded half of the dash illumination worked. Fuel gauge pegged and dummy lights worked. When I ungrounded that wire as you instructed the fuel gauge stopped working all together.

Cluster B fuel gauge doesnt work. Dash illumination doesnt work. Dummy lights work. When a mystery wire was grounded fuel gauge pegged. I unplugged both mystery wires and fuel gauge still doesnt work.

Mystery black wire #1 dash cluster connector pin 6 solid black wire.

Mystery black wire #2 comes out of the main harness also a solid black wire.

If you cant help and your recommendation is to bring it to an auto electrical shop then that is fine. Skinners and damulis is a ford dealer and repair shop. Does this count as an auto electrical shop? If not then I have no shop In a 200mile radius.

If you have electrical diagrams for a 78 then can you send them to me? I have no problem comprehending a diagram. But when I am asked to do tests on things that I have no idea what im doing or if im doing it right then I just get confused. I have stated exactly where the one wire came from. You stated that pin#6 is for lights. Solid black wire and a black wire with green stripe. This is the mystery wire. Where does the other end go to? Im completely clueless when it comes to electrical all I can do is read a diagram and hook wires together.

 

I can't tell you if a dealership I've never heard of can do automotive electrical work. Call them and ask. Probably.

I didn't associate a pin number with any sort of lighting circuit. The point of my explanation was to help you find the ground location to the cluster. Forget I said anything because it is only adding to your confusion, and pin numbers don't necessarily stay the same anyway if the cluster has been changed. That's why I'm throwing in the towel.

I thought you said the mystery wires were solid BLACK. At any rate, solid BLACK with GREEN stripe is an 8.5-ohm resistor wire representing accessory power TO the cluster for the ICVR. The BLACK wire bundled with it is a short dummy wire that's crimped into the terminal because the resistor wire alone is too thin of gauge to sit by itself. This has nothing to do with ground. The short BLACK wire is taped off and tucked away in the harness wrap.

1978 wiring diagrams aren't available in their entirety online, but 1979 are, and the two are very similar. Link: http://www.fordification.net/tech/wiring.htm

Best of luck.

 

Yes the wires are solid black sorry for the confusion pin #6 has 2 wires. 1 is black with green stripe this wire is fine and not cut. The black wire bundled with it is one of the mystery wires. You just said thats a dummy wire and taped off. Ok that solves that wire. I thought 78 and 79 wiring was totally different. So if their close then i should be able to look at my 79 to find out where the other mystery black wire goes? If not I will look at them diagrams.

 

Exactly. It's just a dummy wire and should only be a few inches long. It's purely there for mechanical reasons. It is taped off or over-molded from the factory and should remain that way if not already so.

'78 and '79 are very similar. '77 and '78 are not.

I can't answer that question because I'm not sure what you're working with, but you're better off with the '79 diagram than nothing at all.

In case I had not made it clear, the whole intent of the tests I walked you through was to try and tell if your cluster was grounded properly, because the symptoms you described made it sound like the cluster was not grounded. However, your measurements make the cluster appear to be grounded, which suggest the symptoms you've described are occurring for some other reason. I can't help you troubleshoot any further because you're working with a mismatched system that appears to have been cut up by a previous owner. That's hard enough when you're standing in front of it. It's even harder when you're halfway across the country and you're looking through it through the eyes of someone new to electrical (no offense meant at all).

My parting advice to you, is re-install the original cluster and order a new printed circuit for it. The replacement cluster from the junkyard is not correct for the truck, and may have its own problems too. The pinout changed between the two clusters when the high-beam light was moved to the speedometer and the fasten belts light was added. Without digging through more diagrams I wouldn't be able to tell you if pin numbers swapped around, filled empty spots, or what. It's just an added variable that only complicates the problem. The '79 wiring diagram that's close enough to your '78 truck is not going to comprehend the replacement cluster either.

Stated another way, don't replace something that's bad with something that's incorrect for the application and also possibly bad.

 

Ok thanks I will order a new circuit. One question you said the hi beam light is on the speedometer. Mines above the temperature gauge. Fasten seat belts was above the fuel gauge. Maybe the cluster that was in it was wrong to begin with?

 

An older cluster will have a BRAKE light to the left of the left signal and a HI-BEAM light to the right of the right signal. No FASTEN BELTS.

A newer cluster will have a FASTEN BELTS to the left of the left signal and the BRAKE light moved to the right of the right signal. The high-beam indicator moves to a blue jewel in the top center of the speedometer.

The only other variation I'm aware of is an option for 1975 only. That's BRAKE light on the left, high-beam indicator as a blue jewel in the top center of the speedometer, and LOW FUEL ECONOMY on the right.

You seem to be describing something with FASTEN BELTS and HI-BEAM on the same cluster. That would leave no room for BRAKE. I know of no such cluster.

 

Ok thanks neither cluster is right for my truck then. Where can I oordera complete cluster that has the right lights for my truck? Cluster that was in it when I bought it had fasten seat belts to the left of the left blinker. Oil light above the left blinker. ALt light above right blinker and brake to the right of right blinker. Hi beam light above speedo.

New cluster has brakes to the left of left blinker. Oil light above left blinker. Alt light above right blinker and hi beam light to the right of right blinker. No light above speedo.

So both are wrong correct?

Old cluster has green circuit board. New cluster has orange or red circuit board if that means anything.