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Old 02-08-2020, 08:56 AM
RollinCole RollinCole is offline
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Default Help! My 760 Gauges are on the fritz

Hello all!

1984 760 D24TIC.

I have been having issues with instruments. I have had my oil pressure and level lights flashing at random (UPDATE: this is now fixed, replaced whole engine harness with new) however, at random, my fuel and temperature gauges will drop to zero as if they have lost ignition power. I've tried to isolate the scenario to a set of circumstances but it seems pretty random. I did have some blower motor issues, and I did replace it and for one full day of driving, I had no issues with the gauges, strangely. George, if you're reading this, this is the silver car-- everything behind the dash looks brand new, grounds included.

Does anyone know where the fuel/temp gauge get ignition power?

Thanks!

Last edited by RollinCole; 02-08-2020 at 09:02 AM.
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  #2  
Old 02-08-2020, 01:10 PM
v8volvo v8volvo is offline
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Been a while since I have had one of those clusters apart but to my recollection there is a little voltage supply unit somewhere on the back of the cluster that feeds power to those two gauges, since IIRC they run at less than 12V. Maybe if that unit were failing or if it had a crack in a cold solder joint, it could cause the gauges to temporarily quit working?

When the fuel and temp gauges drop to 0, does the speedometer and tach and warning lights still work fine? In other words, it's just the fuel and temp gauges that seem to be having a problem?

If you slap the dash or somehow shock the cluster, does it ever get the gauges working again, like there's a loose connection that is getting jostled?

I'm pretty sure the whole cluster gets power from one source and then distributes it to the different gauges so don't think it could be a fuse or circuit problem but can double check on that. Think I have the greenbook diagram somewhere for the cluster.

One thing you might try would be swapping in a known good different cluster temporarily, to see if the issue disappears with a different cluster. I think I have a spare one for an '84, worst case scenario I'd be happy to send it to you and you could give it a try.
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Old 02-08-2020, 05:26 PM
RollinCole RollinCole is offline
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Great to hear from you and hope all is well! The only thing I can sort of say agitates the issue to happen, is having the heater on high temp (auto climate) but not selecting a fan speed. Once the gauges go, no amount of tapping or dash pounding restores them. Yes, only the fuel/temp gauges are affected. Engine harness fixed the rest. The only thing that seems to restore the gauges to working again is letting the car sit for a while while or, cool down? I thought maybe solder joints. I’ll steal a cluster off anders soon hopefully...👍🏻
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Old 02-10-2020, 10:55 AM
v8volvo v8volvo is offline
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I think you're probably on to something with it being related to temperature. The air ducting to the defroster outlets and some of the dash vents runs pretty close to the back of the cluster so the cluster could be affected by them. Maybe when the HVAC temperature is cranked up and/or the car has been running for a while and the inside of the dash gets good and warm, the heat is letting a solder joint open up and lose contact, or the heat is knocking out that little power supply unit for whatever reason.

Trying another cluster sounds like the simplest next step... if a different cluster has no issues then you know where the problem is. I think those early '84 clusters are somewhat unique, but any year 700 series diesel cluster would probably plug in and work at least to test with.

Good to hear that car is in good hands! Would be fun to see it again one of these days.
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Old 02-13-2020, 08:46 AM
v8volvo v8volvo is offline
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Turned out I did have a greenbook for instrument cluster and believe it or not, it describes the exact problem you are seeing and what can cause it. Images attached. It sounds like specifically for 1982 through 1984 clusters there is a little built-in voltage regulator unit that is meant to provide a stable 10 volts to the fuel and temp gauges. It says if both gauges are faulty, that is typically the reason for an 82-84 cluster. Guess it probably is intermittently failing, or maybe has a loose connection that you would be able to find.

Section "S22" describes how to test it and to replace it if there is a problem, could be tricky to test if it fails intermittently but given the symptoms maybe you already know enough to incriminate it. Don't know how you'd get a replacement for it now other than from another donor early cluster, pretty sure I have a spare cluster out of an early '84 gasser that might be able to provide one if you or Anders don't find one closer. Or maybe it is even a standard type of electronic part that a Radio Shack or similar could supply a close enough replacement for.

These are from manual TP 31166/2 published 11/88, pages 71-73.
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  #6  
Old 02-18-2020, 05:46 PM
RollinCole RollinCole is offline
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Huge help man! Been off for a few days but here’s what’s been happening:

Swapped in a somewhat “good” cluster, but it was a 371,000 mile cluster and turns out the speedo was dead, and it had some short circuitry going on, so I plugged the original back in and hoped for the best. I originally thought an EGT gauge plugged in to the naked connector (I’m assuming for the gas application, four pin not used) was the culprit for shorting out the gauges in the dash, nonetheless, I have fully weighed it out, the same thing happened again after turning the heat on. Sounds like Tacoma speedometer will be my next move and have them inspect those diagrams you provided. A huge thanks for the brainstorming, I’ve been ripping my hair out over this one because they are two values I can’t live without being reliable. I think it’s been on the way out, though. The temperature gauge seems to peak on the high side at times with no real relation to the actual coolant temperature so think something is definitely overloaded. I’ll report back if I need a cluster, hold on to it! Hopefully I can swap the speedo...mine still has the nice 76,000 miles on it
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Old 02-18-2020, 08:12 PM
RollinCole RollinCole is offline
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Also, if you come by XXX on March 22nd you can see the fresh new engine and some other tasteful mods done do it! I also (somewhat secretly) have the US-Rare MK18 Ocean wheels on the way from Sweden topped with some coilovers for the extra-Swede look. Probably the coolest most fun Volvo I’ve ever owned. I also have all that paperwork you passed along with it; what a cool story, the previous owner had good taste, he just didn’t drive the thing enough! I’ve done most of the old-car suspension overhaul work so far and I’ve toasted a rebuilt engine and swapped in the fully-built new one with Anders and it’s been pretty good so far. Lots of good power and fairly dependable, but it keeps it interesting. Daily driver.
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Old 08-30-2020, 05:23 PM
RedArrow RedArrow is offline
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Default Comment on CLUSTER PROBLEMS. My Voltage gauge AND Temp gauge

Quote:
Originally Posted by v8volvo View Post
Been a while since I have had one of those clusters apart but to my recollection there is a little voltage supply unit somewhere on the back of the cluster that feeds power to those two gauges, since IIRC they run at less than 12V. Maybe if that unit were failing or if it had a crack in a cold solder joint, it could cause the gauges to temporarily quit working?

When the fuel and temp gauges drop to 0, does the speedometer and tach and warning lights still work fine? In other words, it's just the fuel and temp gauges that seem to be having a problem?

If you slap the dash or somehow shock the cluster, does it ever get the gauges working again, like there's a loose connection that is getting jostled?

I'm pretty sure the whole cluster gets power from one source and then distributes it to the different gauges so don't think it could be a fuse or circuit problem but can double check on that. Think I have the greenbook diagram somewhere for the cluster.

One thing you might try would be swapping in a known good different cluster temporarily, to see if the issue disappears with a different cluster. I think I have a spare one for an '84, worst case scenario I'd be happy to send it to you and you could give it a try.

Hi,

I have a very similar issue.
In my case it is the Voltage gauge and the Temp gauge.

It used to be the Temp gauge only, acting up since many yrs ago.
A knock (1 gentle tap) on the lower lip of the instr cluster (right in front of the temp gauge `platform`) usually (=always) fixed it then it worked for the trip. This changed.

Recently it happens more often and the Voltage Gauge joined the Temp gauge in doing it. The knock usually fixes both...but often it needs more than one knock, or one that`s stronger than a gentle tap.
A single knock still helps but not always....at the same location or near the Volt gauge, or at both gauges... then it works for a while.
But then, it sometimes happens again on the same day/trip.

These two gauges BTW are out pretty much every time I drive the car now. The cluster needs the knock... almost every day.



I used to have the large panel/cover removed from below the steering wheel (above the driver`s knees) and I kept it like that for many years... I was lazy to put it back for a long time but recently reinstalled it a few months ago. As you said, this is probably the reason why it does it more often (maybe there is more heat around the instrument cluster).

It is super annoying, I will take the cluster out and inspect the solder joints.



My speedometer and tach, lights, etc everything else in the cluster works well despite those two gauges (Voltage and Temperature) being out. ((They aren`t out all the time))

Extra info:
The fuel gauge works abnormally, shows low when full and shows full when empty. And not sensitive to the level. It is either at left or middle or at the right side. That gauge is not related to the other gauges, I think. Maybe wrong wiring or mismatched connectors at the fuel tank, I have no idea, I just learned to live with it.
But having the Temp gauge is the minimum d24 health insurance.

(Exra info: In my 1986 740 car, the voltage gauge is the left upper corner. The fuel gauge is below the Voltage gauge.
The temp gauge is on the right , it is the lower corner of the instr cluster (below the turbo gauge =top right)

Could you please circle the voltage stabilizer on the third illustration? Thank you.
I will take a picture of the back of the cluster or a spare td cluster I have. So far, I replaced one of the four Yazaki larger bulbs because it was out (from the knocks the temp gauge needed)

I will compare the fuel gauges of my spare cluster with the one in the car, and probably try swapping them to see if the spare fuel gauge will work in my cluster or not. If you think the problem lays somewhere else, pls let me know so I can save some time.

Last edited by RedArrow; 08-30-2020 at 08:02 PM.
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  #9  
Old 08-30-2020, 08:39 PM
ngoma ngoma is offline
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RedArrow, your issue may be a little different. Are your gauges at zero from startup? And you get them to pop into action by hitting the dash? Or are they working properly, then intermittently drop to zero while already driving?

Because turbobricks already has a fix for scenario #1, it's different from scenario #2.
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  #10  
Old 08-31-2020, 08:24 AM
RedArrow RedArrow is offline
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Default 3 gauges are hallucinating lol

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)
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Last edited by RedArrow; 08-31-2020 at 09:40 AM.
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