[RedArrow]

That question made me think twice about what exactly `usually` happens. ``Yes and no.``

Well, most of the time, when I start the car, the Temp Gauge USUALLY will not move (not bc engine is cold but bc gauge is `off`.
Knocking once or twice in front of the temp gauge used to fix this then it was okay for the rest of the day/trip. ((Currently it is not yet always necessary to knock it but at least 30-40% of the time. ))

Rarely, it would also just quit as I`m driving and drop to zero then stay there until I tap the area again.

BUT lately it is more like this:
1. temp gauge doesnt show temps until the knock happens. (sometimes it has a positive attitude and it works all by itself though)
2. as I drive it quits, often more than once (vibrations? heat in dash?, IDK)
When they quit they just go to zero like someone shut power off. When they return they return straight where they have to be and remain there and show accurately. It must be some kind of an electrical problem, I`d put my vote on bad solder connections or the cluster has a sensitive spot (made out of plastic and 36yo, high miles too. But, all lights and all feedback lights do work, whatever is in this cluster ==works.
3. Voltage gauge joined the temp gauge but the volt gauge doesnt require the knock more than once. If it needs a knock to start, it is ususally when the car was started for the first time in the day, then it works well for the rest of the day/trip. Only a few times, when the temp gauge quit it took with it the voltage gauge too. Rarely but it happened too. As I said, most of the time the voltage gauge is a reliable 1-knocker (as the temp gauge was but by now it needs more than 1 knock).

4.I noticed that often my knock at the temp gauge will make both gauges work just fine. Then, the voltage gauge remains active but the temp gauge may quit repeatedly. A knock always puts it (or them) back to work.

5. The fuel gauge doesnt seem to be affected, at all. It just does its own game: showing the opposite of levels full/empty. No matter what the temp and voltage gauges do, the fuel gauge lives its own life.
BTW, when the tank is fully filled, gauge is in the red (showing Empty)... It starts climbing towards to the right (`Full`) when the fuel level is about half a tank. When actual fuel levels are getting to about a quarter of a tank, the stupid gauge sits `in the middle`...but then it sits there a lot until there`s no fuel left, when the gauge finally reaches the right side and shows FULL (but in real life it actually means EMPTY).
Sooo weird...but it works like that, pretty reliably. So I do know when it starts climbing I have about 1/4-1/2 tank of fuel left. I watch the counter too. At full fillup I zero it down and drive till I reach about 350-375 miles (or less if I idled a lot).
But, once, the stupid fuel gauge did not start climbing and I wasnt sure about my fuel level so I broke down on a highway and had to get DIESEL fuel (as always: at night, far away and not locally, in a residential neighborhood, no gas stations open, the open ones with no diesel, rainy weather and with an annoyed GF late at night AND in big traffic = THE nightmare lol). I poured a bottle of ATF in, it gave me some juice but not for long enough to leave the highway (uphill too). UGHH.

Anyways, in a nutshell, i want to be able to have these three gauges work accurately. Also I`d like to keep my existing cluster because it shows a proud 442.000 miles.
If they match, I may swap in the fuel gauge section from the 1985 TD 740 cluster (the one I kept from the good running 1-owner sedan). I believe my cluster in the red td car is originally a 1986 gasser car modified cluster with add-ons for the td engine, prob the glowplug feature, i guess. Most of them look identical but iDK yet, have to put them side by side to see and decide)

THE FIRST PICTURE IS THE ORIGINALLY GASOLINE CLUSTER IN THE 1986 TD SWAPPED RED CAR. Engine was cold so the temp gauge is in the left position. Fuel gauge showing `FULL`.

THE FOUR OTHER PICTS ARE SHOWING THE OTHER CLUSTER (SPARE FROM 1985 740 FACTORY TD)