This is a bit of a strange one. My stock gauges worked flawlessly until the other day. The only thing that changed was new alternator and harness for voltage regulator. About three days later I put my ebrake on and my cluster went dark, and I lost my VM, fuel gauge (dropped full to half on a full tank), and tachometer. I replaced the fuse and got my cluster illumination back but bubkus on the gauges. Is there anywhere else to look? I unplugged the ebrake switch cable, looked for loose wires or chaffed wires. Is it possible the ebrake shorted and did more damage than just blowing the illumination light? I have never had the dash out on these older gen trucks. Any tips for when I get home and have time to look into it would be much appreciated. It's an 89 F250 7.3 IDI. All fuses are working, all lights work, radio, etc. Just those gauges failed all at once immediately with pressing the ebrake and haven't returned.

 

ebrake is that emergency brake or electronic brake controller for trailer brakes?

 

Pressing the emergency brake will switch the single wire to ground to turn on the red indicator light in the dash. If the indicator bulb is shorted internally then I could see why a fuse would blow. A shorted bulb is rare, but can happen.

 

Sorry it took so long to reply. Yes when I say ebrake I mean the parking brake not a trailer brake system. So basically when I replaced the fuse my dash illumination returned but still no gauges. It's interesting you mention the park brake light causing a short, because I just realized there is no parking brake light anymore. I will definitely look into that when I finish my road trip and make it home. Is there anything on the dash that can "fry" causing the gauges to stop working outside of a short from the bulb for example or am I looking at trying to find a new cluster basically?

 

the back of the cluster is a printed circuit. if the parking brake light somehow shorted out, it possible could burn the ground wire rendering the cluster nonoperational. but i doubt that happened, because you still have cluster lights.
i know these trucks used a constant voltage regulator through 1986 model year, but not sure for the 87 and newer trucks.
the constant voltage regulator dropped voltage to the gauges down to around 5 volts, and was used in the instrument cluster for for the volt meter, and fuel gauge.
they tend to go bad.

as far as the tach, check to see if the sensor is plugged in.
i am not sure if tach power was through the CVR, or was straight 12 volts.

 

I'm working on a reply but I have to take a break. Don't be concerned about the e-brake light, the existing problem is not related to that, it's probably not burned out but at this point it doesn't matter. The gauges and tach. are all powered from a single different circuit branch. My last thought in my personal upcoming diagnosis was a ground connection from the instrument panel, a common ground that is for the gauges and tach. if there is one, since they are all on the same power supply circuit I thought that they might have a single common ground wire connection from the instrument panel . I don't know IF there is one or where that ground wire would be attached but I'll look it up later in some wiring diagrams and info.

DO disconnect the power from the e-brake switch and you may as well remove it for closer inspection and testing to confirm if that is the problem. There is a chance that it might not be.
There are LOTS of things on the same power circuit that powers the e-brake switch - it's just at the end of a branch. If the switch is bad the light will probably not come on anyway, nor after the switch is disconnected, HOWEVER, you SHOULD test the power wire that comes to the switch with a test light clamped to a good ground to see if the wire does supply voltage. That will help in the diagnosis, just something quick to rule out.

My approach is going to start at the Start Relay on the inside fender well, all of the small wires that go through the main engine harness. until I can get far enough into wiring diagrams to point at specific wires to check (that's going to take quite a bit of time) About 90% of the time, electrical problems that occur after an electrical repair, like what you did, are related to something that occurred during the repair. Those wires were disconnected, moved around and re-connected so that's where my approach will start, and with a Test Light.

In the mean time YOU SHOULD examine those small wires very closely between the Start Relay and the main engine harness plug for any defects or bad connections. If I remember correctly, one of the main wires to be tracing will be RED with a GREEN STRIP or light-green stripe.
Also be testing the fuse links in case it is one of those.
We'll also be testing if the wires to the gauge senders and tach. sensor to see if those wires have voltage (probably not) and if the problem has not been found, from there it's back toward the firewall and through it into the cab.

The gauges and tach. are apparently not getting voltage so we'll try to figure out why. I wouldn't worry about any expensive or complicated damage, it's probably something easy to fix or replace.
I don't know the answer(s), I'm just going to try to help with how I personally would approach the problem.
More later

 

That's interesting Tom. I just removed and repaired my whole wiring harness from where it comes up from in front of the battery, to the start relay, through the main harness connector and all of senders, tach sensor, glow plugs etc. New alternator, voltage regulator glow plug controller & misc. I went over those wires so many times I should remember every one and what they did and where they went but DUH! I don't remember it without going out and looking at it all which I can't do right now. It took at least two weeks to get all of that done! The harness and what I was attempting to do with the best of two complete harnesses to work with presented a lot of complications that I had to resolve.

I thought about that voltage regulator that the OP (Original Poster) Raven Point installed and wondered if the existing problem might be related to that. I think that they operate the same as you described and I have heard of them going bad or failing after being installed but the one I installed is supposed to have alot of built in protections. I assumed that Raven Point did the job correctly, made sure to do it correctly or he probably wouldn't have done it himself. I'm hoping the issue will be something easy to find and fix.

 

Did you find the problem? The wire that supplies voltage to the gages and tach. warning indicators, etc., is Red/Yellow-stripe, not Red/Green-stripe. It is not the same circuit as the i/p illumination. I did look at most of the relevant wiring diagrams on July 19 and location of splices and grounds. I was waiting for you to update where you are at with this as I think you wrote that you were 'on the road'. I didn't want to post the images unless they are needed because I've posted so many I'm concerned that I'm near the limit. I did notice that I've already posted one of them a couple of times so I'll link that directly and post a new one below it:






CHECK to see if you have voltage coming to the 15 amp fuse location(s) at the Fuse Panel which have been mentioned earlier. If not, which I would suspect) the problem will be in the wire circuit coming to it from in the engine compartment. You wrote that 'all fuses are working' but you won't know that if the fuse socket isn't getting voltage.

Splice 404 (S404), the book says is located 'Near clutch switch T/O' That term "T/O" is used often following the location of splices and I have NO IDEA what 'T/O' means. I've searched the web and gone through long lists of abbreviations and acronyms including those used in automotive and electrical I still can't even guess! That's going to remain a mystery until someone reveals it's meaning.

I hope that helps to find the problem.