Hey everybody! Just joined the club yet I've been here many times reading others questions and solutions. I've looked for the question that I'm going to ask and haven't found the exact same problem posted. I have an 89 245 it has over 500,000 on it now and has been my truck(overload coils on the back) for almost 20 years. As long as I've had it it's had this gremlin, I start it, start driving, look at the dash and realize that the speedo, gas gauge and charging system aren't working. Somehow I figured out that by simply turning off and then back on the lights that the above will all start working again!! So I've been doing this for 19 years and it's always worked so why mess with it, well it doesn't work any more. Sometimes when I start it everything is fine yet sometimes not and I haven't been able to drive it because of the non charging. Has anybody else ever heard of or had this problem and figured it out?

Thanks in advance!

Slap the top of the dash above the instrument cluster. If that starts it up, check the tension on the three-pin L-shaped plug at the back of the speedometer -- its locking anti-tamper clip is probably long gone.

If the slap doesn't do it, the ignition switch is the next most likely fix. First, try gently wiggling the key while the car is running.

A third possibility is someone worked on the cluster (what 20 years ago?) and left a loose screw where its flex fuse is attached. This is the only fuse protecting the circuit you're losing, and not one meant for owner replacement.
--
Art Benstein near Baltimore

If speed counted, rabbits would rule the world.

Gentlemen! Thanks Machine man,Art & 3peat all great answers. I checked the D+ wire a year or so ago and all checked out. As far as the ignition switch (and the light switch I might add) I disassembled both of them and cleaned contacts etc. this summer and the little gremlin remained! Oh and by the way yes sometimes smacking the dash did the trick when the headlight trick did not. After I posted the post the other night I went to Turbo bricks and found some stuff on the cluster and bad solder joints. The post was based on 740&940's clusters and explained that after 30 years solder joints sometimes get loose. Wahla! The 240's cluster is different as one has to disassemble the board from the back of the seen instrument panel in order to see the "printed circuit" board. And there was the gremlin, the post from the flex fuse had become lose in the solder connection. Nailed it Art! Interesting enough every other joint looked to have a roll of solder per joint except for that one! Thanks again guy's and hope everybody enjoys the holiday season.

Now- 89 245,87 245(Parts car), 91 240. Past- 92 740, 91 940 blacked out turbo wagon(that was fun until the X got it ! )

Cheers!

Nice work.

In case anyone else arrives here with the same issue, I'll include these pics which I've often posted for those trying to find the path of the B+ through the speedometer, cluster board, and eventually to the warning lamps and D+. I'm guessing your trouble with the solder was either at #1 or #2.





These pics are of a cluster for an 89. Every year is a little different.
--
Art Benstein near Baltimore

We childproofed our homes, but they are still getting in.

I will add to Art's comments that my ignition lock cylinder recently wore out at the 422K mark and it was causing me all sorts of similar start-up electrical gremlins. I would start the vehicle and the overdrive button would be on (and wouldn't go off), or the front lights wouldn't work, or the windows wouldn't go down or the back brake lights would not work. It turns out it's a common symptom of a worn out ignition lock cylinder and as Art mentioned, one of the first type of things they do to test the assumption is - w/the vehicle off - to turn the ignition key ever so slightly backwards in the lock cylinder and if the windows, lights, etc. suddenly work, then the cylinder is worn out. There are supposedly copper plates inside the cylinder that rotate with the ignition key and with time, these copper plates wear down. I spent the whole summer picking out and cleaning specific fuses thinking that was the cause....

Hi,

Yes, that is a nice trick of using headlights to make the alternator kick in.

Part of that charging system is through the battery light in the cluster. The light circuit goes to ground via the alternator's housing and a separate grounding wire.
I would check that out and the D+ wire on the alternator that comes from the dash.
It carries "exciter current" to kick the alternator some juice in its first few spins.

Backing up to the cluster now.
You have a fuse panel and one of them feeds the cluster and the cluster has to have its own grounding wire to make all of the other functions work.

I can only speculate that somehow turning the headlight switch gives something a grounding path through its circuitry. Maybe it via the parking or turn signal lamps coming on.


It all sounds pretty wild!

Phil