88 745 - Erratic instruments.

[dustyv]

Hi Guru's,
My 745 has currently developed an instrument fluctuation.
Viz: Switch on ignition all (in particular) dial needles move, when engine started, they move some more.
I know that my speedo is running + 5 MPH more than it should, i.e. reads 35 but is actually doing 30, that is consistent throughout the speed range.
The most noticeable mover is the fuel gauge, if the tank is full, at the igniton on stage it read 3/4, started moves up to full.
Is there a simple solution?
Appreciate any and all advice.
Thanks.

[v8volvo]

Sounds like you might want to check your charging voltage. You should read somewhere between 12.5-13v at the battery terminals with engine off, and 14v plus or minus a bit with engine running.

Is the fluctuation random, or is it just a difference between when the key is on with engine off vs when the engine is running?

Do you notice a corresponding fluctuation in the brightness of the dash lights, exterior lights, tone of the door chime, etc, or do you see it only in the movement of the instruments? If it is isolated to the instruments only, the little 3-pronged power supply board on the back of the cluster (in the middle behind the speedo) may be something to check for corrosion, loose connection etc.

[raw]

Could this be to do with a voltage regulator of some sort in the instrument cluster? I have heard they can be problem items I'm sure, but I don't know what the symptoms are.

Richard

[RedArrow]

Hi Richard,
I had once similar symptoms, except my speedo was not acting up as yours does. I got Volt gauge things and dash lights dimming things going on last year.
It`s interesting because I experienced something similar to your issue, but only later I knew how it disappeared.

Ok so I had those two lower PS pump bushings VERY worn, cracked, so much deformed (still not visible at insp!) that ps belt was not running in a straight line (misaligned) ; all this made the pump tilt a bit, pulled upper bushing out towards front, a few millimeters, etc etc , leak some, etc, chain reaction
When I finally replaced bushings there, I removed both ps belt&alternator belts for service, changed ps bushings, fixed the leak, flushed atf fluid in pump, put belts back on, retightened&adjusted them both, positioned alt&ps pump...it helped belt align MUCH better, also my Voltmeter wasn`t going crazy afterwards (sometimes it was showing relatively too low, too high, too `SLOW` etc), instrument cluster lights stopped dimming on their own.
It suggests that in my case IF ps belt is too tight or loose, that can/may affect (I think) alternator`s effectiveness. Strange. That time I did so many check ups and fixes that I cant recall whether it was before or after, but my battery needed fluid as well. And terminal connection wasn`t tight enough. I like going through things, inspect and hear things but problem is we always find something to fix. Joy of having an old brick and Swedish-German magic.
Just an example : my fuel gauge works totally opposite as it should: shows empty when tank is FULL of diesel, until having only half tank of fuel, ...at about 7G left in car it moves to `Center position`, later it starts climbing to show `Full` as smoke flies out my exhaust (=tank goes empty). Strange. Hey It`s always very accurate at half tank!

[raw]

Hi, I'm not the OP on this thread, but what you say is interesting to me, as I've always thought my belt alignment doesn't look quite right, seem to be leaking power steering fluid slowly and have a Winey pump, and have had both belts throw them selves off on two random occasions, months apart, and both have been fine for four months since (touch wood). However, I don't suffer any gauge issues except for a totally dysfunctional flue sender that I know about.

Maybe I need to have a look at those belts, although I'm sure the set up is different on the TIC setup :/

Richard