Sudden loss of tach and no power

[Ron]

I pulled fuse #5, which is the fuse for the dash instruments, while the motor was running and it reacted EXACTLY like it did when I lost my tach signal the other day. I revved the engine and it sputtered and wanted to die. It would idle just fine though. I reinserted the fuse and everything worked again like normal.

The alternator light stayed on for a few seconds and then switched off, which tells me the car was running off the battery and not the alternator. Makes sense if the alt light is out in the dash.

My battery puts out 14v, however, it is coming up to 7 years at this point. I'm also using a 10 amp fuse for #5 while online it shows a 20 amp.

I can see the 10A fuse getting hot and causing the holder to get weak/bad connection.

I'd swap the fuse, and if it is currently working, do some shake & wiggle testing...

Next time it does it, while the gauge and warning lights remain dead, try not to disturb anything you don't have to and check in order:
12V @ Battery
12V @ Aux Relay2.Brown
Ground @ Aux Relay2.Black
Turn key to Run.
12V @ AuxRelay2.WhiteA AND AuxRelay2.WhiteB
12V @ Fuse1 AND Fuse3 AND Fuse4 AND Fuse5 {See * below}
12V @ Otterstat.Green
12V @ Cluster.Green {Terminals 3, 9, 20 }
Ground @ Cluster.Black {Terminals 13, 17}

A failed test means you just passed the problem.

* Gently probe from Battery(-) to each hole in the top of the fuse.
(You might have to use a piece of small diameter wire to fit down into the hole.)

[bytes311]

I can see the 10A fuse getting hot and causing the holder to get weak/bad connection.

I'd swap the fuse, and if it is currently working, do some shake & wiggle testing...

Next time it does it, while the gauge and warning lights remain dead, try not to disturb anything you don't have to and check in order:
12V @ Battery
12V @ Aux Relay2.Brown
Ground @ Aux Relay2.Black
Turn key to Run.
12V @ AuxRelay2.WhiteA AND AuxRelay2.WhiteB
12V @ Fuse1 AND Fuse3 AND Fuse4 AND Fuse5 {See * below}
12V @ Otterstat.Green
12V @ Cluster.Green {Terminals 3, 9, 20 }
Ground @ Cluster.Black {Terminals 13, 17}

A failed test means you just passed the problem.

* Gently probe from Battery(-) to each hole in the top of the fuse.
(You might have to use a piece of small diameter wire to fit down into the hole.)

Solid advice. Thanks Ron!

[bytes311]

Just to follow up for any future readers: The ground cable to the battery was barely hanging on. Apparently it had worked itself loose over time. I went ahead and replaced the 7 year old battery and tightened the leads nice and snug. I have not experienced a problem since.

[bytes311]

Last (hopefully) follow-up because this happened to me again. But I think I finally found the culprit!

Yesterday I drove my car to work where it sat and heat soaked for quite a few hours. When I went out to my car to start it... no tach signal. I could usually get it working again if I played with the ignition key, but this time it wasn't having it. The car started and ran, but it felt like a miss with piss-poor acceleration. And if I put any load on the electrical system (headlights or AC), I'd hear an audible popping/arching-type sound from the distributor area. Weird.

After working up the courage to limp my car home (I live just 5 minutes from work), I made it home safely and pulled out my multimeter. I went through Ron's testing procedure and passed ALL the tests. I even swapped Ignition ECU's, to no avail. Next, I moved on to the alternator. I found it wasn't putting out. So I messaged a buddy of mine and he asked if I ever inspected the printed circuit board behind the dash cluster. That got me thinking about the battery light. It dawned on me that I wasn't getting a light with the key in the "on" position. So I proceeded by smacking the side of the dash. Suddenly, my batt light and tach came back to life!

Today I am placing an order for a new printed circuit board.

[David T]

It could just be a bad connection of the plug to the PC board, the PC board may not be bad. Most of the time you can make it work just by cleaning up the connections. While you have it all apart change the light bulbs. Do NOT use an LED bulb for the alternator warning light (in case you are planning to change them over to LED).

[bytes311]

It could just be a bad connection of the plug to the PC board, the PC board may not be bad. Most of the time you can make it work just by cleaning up the connections. While you have it all apart change the light bulbs. Do NOT use an LED bulb for the alternator warning light (in case you are planning to change them over to LED).

I've had the dash out before (years ago), and swapped the lights for LEDs, minus the batt light. CA roads are not nice to our cars. The connector may have worked itself loose over time (or perhaps I didn't seat it properly).

[MrChocky]

I've had the dash out before (years ago), and swapped the lights for LEDs, minus the batt light. CA roads are not nice to our cars. The connector may have worked itself loose over time (or perhaps I didn't seat it properly).

Yeah. I think also after a certain age, the PCB just doesn't survive removal; the connectors get fragile; I've had to replace 2. One problem I had too was not putting the screws on properly - this caused my tach to jump around.