Caution - long post!

The truck - 1990 XLT 5.8 automatic E4OD Runs great!

Today I had the day off and drove out with my dog to the mountains. I had parked for a while at a campsite while my dog played and investigated whatever it is that dogs investigate. After I decided to move on, when I started the truck, I noticed that the voltage gauge was not working. It was all the way over to the left. I turned the motor off and back on again, and got the same thing. Then after I started driving, I started tapping on the dash near the voltage gauge and it went back to where it usually sits. But, I kept my eye on it while driving and sometimes it moved wildly when I hit a bump and sometimes not; and sometimes it would just freak out and bounce back and forth crazily for seemingly no reason. Also, the other day I noticed the gauge move wildly when I released the parking brake, because of the vibration of the dash from the pedal snapping back up.

I am pretty sure that the problem is in, or near, the gauge, as I can make it come back sometimes by rapping on the dash, above the gauge. The truck does not appear to have a battery or alternator problem, I drove for over an hour to get home with the lights and the heater on, and it started right back up again afterwards.

Somebody a while back recommended an instrument panel voltage regulator to control wacky gauges (sometimes the oil pressure gauge fluctuates a little, again for seemingly no reason, it is not related to engine rpm's or temperature). So I bought the regulator from NAPA - and found out the hard way that there is no instrument panel voltage regulator on a 1990 Bronco (I don't know what NAPA was thinking when they sold me a nonexistent part...).

So, I went over to my local Ford dealership to see if I could buy the actual gauges to put into my instrument panel to replace the old ones, but he said that he could not get them for my truck and even if he could, it would be around $250 for all four! I then asked if I could order a brand new OEM cluster, but he said that he could not get one of those either.

Sooooo guys, what is my next step? I've had the cluster out before, around two months ago, when I was searching for the nonexistent voltage regulator - and made I sure that all the connections were tight. But that does not necessarily mean that something is not loose now.

Other people have spoken of grounds - but where exactly is the ground that grounds the cluster? I have a wiring diagram at home, I am not at home now, but the Bronco is with me so if anyone knows what grounds I should check, that would be very helpful.

On the other hand, does anyone know where I could buy a brand new instrument panel cluster? Does anybody in the aftermarket make them now? I am hesitant to get a cluster from the boneyard - I could end up with the same problems or worse.

If anybody here has one (with tach) and they know for sure that all of the gauges work properly, I would be interested in purchasing it. But I really would rather fix mine with new parts, if I could get them.

BTW - I have a 160 amp alternator, not a one wire; but it is wired a little differently from a stock one. Also, as far as the oil pressure gauge, I have replaced the sending unit twice and always have the same result.

I also do not want to replace my stock gauges and have a bunch of non-working gauges sitting there staring at me while I have the new ones mounted on the dash somewhere. I realize that the gauges in my truck are not the best, and are close to being glorified idiot lights, but they are still useful to get an idea of the state of my truck. If they always go to where they should be, then I know there is not a problem. At 128K, I am not interested in knowing my exact oil pressure as long as their are no noises from the motor. The day that I lose pressure will be that day that I do a rebuild anyway - and it runs so sweet now that I would really like to have my factory gauges working properly.


Thanks for plodding through that lengthy description, but I like to provide as much information about the problem as I can up front, to make it easier for someone to help me figure it out.

 

sounds like a broken trace. i would go to a junk yard and get a used one. if you can't find one i might have one but shipping would probably be more than it is worth. i live in Ohio.

 

What do you mean by "broken trace?"

PS - If you had a cluster, shipping would less than $10 to Colorado from Ohio. I do a lot of shipping because of my small eBay business (and I mean small!) so I am up on shipping prices. But my auctions help to pay for things for my truck and my bike.

 

the little thin ribbon like wiring in the cluster. i will look and see what i got. if i got it you pay the shipping and its yours. let me know what gauges ya got.

 

Flexible circuit boards are easy to trace (once you get it out ) a multi meter and a little time you may need to flex the board to open the broken part of the trace/ circiut it is also easy to fix with a Soldering iron just becareful not to over heat the board and melt it

 

Typical bad guage- a prob. we saw alot of the time in 87-91 F150s and Broncos, came in pods of 2- needed to tell dealer with or without tach and which guage. Easy way of testing???? was tap (beat) on top of dash.These didn't have a constant voltage regulator on back of cluster, may had a slosh module on back of cluster for fuel guage though. And ribbon on back of cluster is wires imbedded in a plastic sheet for everything elec. in cluster, have heard some people call it a wire trace

 

Printed circuit cards start out completely covered in the copper (or whatever alloy) cladding you see that makes up all the little "lines" that run between components on the card. When the card is manufactured, the location and shape of each of these "lines" is TRACED and every OTHER part of the card is etched with an acid to remove the copper. What remains on the card are the TRACED lines. These "traces" then have the components on the card soldered to them thereby creating the circuit card. The "traces" are capable of flowing electricity safely without the need for an actual piece of wire which would take up a LOT more space and weigh a LOT more.

Traces can break with age, overheating, warping of the circuit card, etc. but, as was already mentioned, can easily be soldered back together at the break with a careful solder technique.

Just a little lesson in electronics for anyone who cares to know.