Dash Volt gauge not accurate

[JhwShark]

I am looking for input on any method to calibrate the gauge. I have 12.8v at BAT, jump post, and at Central Electric Board 3 primary Red leads. However, the gauge seems to be ~ 2v low. I have also cleaned Grounds.

I had the instrument cluster out a while ago replacing odo gear and did not see any calibration screw. Any suggestions??

Thanks,
Jon

[EIPtuningR32]

i know mine dances around like a dogs tail. i know that the gauges have some of these plastic gears in them that can wear out and cause inaccurate readings/not to work at all.

[Mrmerlin]

wel you could take the needle off and reposition it, you can use a fork with a rag under it to pop off the needle

[JhwShark]

Originally Posted by Mrmerlin

wel you could take the needle off and reposition it, you can use a fork with a rag under it to pop off the needle

Yup, thats how I took the spedo apart to replace the odo gear. I was hoping of another alternative. By repositioning the needle when the car is off the needle is not in the normal off position though.

Any where to get replacement needles...just in case??
Thanks,
Jon

[Danglerb]

The voltage gauge is not likely the fault, keep looking for poor connections between it and power that measures correctly.

[Stoolie]

I don't think I've ever seen mine above 10v - so I'll check my grounds etc. Also, I noticed today that the water temp meter was jumping between the post and 90°C - flapping around like a fish out of water - would this be consistent with bad contacts at the pod end, or should I check the thermo end first?

[JhwShark]

Originally Posted by Danglerb

The voltage gauge is not likely the fault, keep looking for poor connections between it and power that measures correctly.

Will do, I do not feel it is the gauge (from experience with lots of electric components), it behaves as it should. It just reads low, thats why I cleaned ground points, though they were all clean. Rail 30 has the 12.8v at the CE panel from each of the three inbound Red leads.

I just need to figure the route from the gauge to its contact points along the way. I only have an '84 wiring diagram to use on my '79 and have challenge reading the path.

I suppose I can clean the contacts for the connector to the Instrument Cluster.
Anyone able to tell me the color of the lead from the connector to its next contact (I believe that would be to the CE board).

I do not want to pull the CE board unless I have to...you never know what can happen when you move a board with lots of contacts that is 30 years old (though only 85k miles). But I do want to trace the circuit...you got to do what you...

[928SROCK]

ive got a 1980 auto and when i start it up the volts go up to the 12-14 level and after it warms up and i step on the brake the volts drop to 0 any thoughts?

[mood]

I have a spare instrument cluster from a USA spec '87 and it has a potentiometer on the back of the voltmeter, my '82 euro S doesn't have that. From what I've seen with my car, the voltmeter is significantly affected by large electrical loads such as the cooling fan, headlights, and brake lights which barely affect actual voltage measured at the jumpstart point. My voltmeter also under reads by around one volt which only makes matters seem worse. I'm sure there were a lot of complaints to Porsche service centers about indicated voltage so Porsche ended up making the voltmeter adjustable.

[Normy]

First of all, are you reading the voltage at the battery? 12.8 volts is about correct...engine off.

Engine ON it should be 13.7....

-You need to replace the "foil" electronics on the back of the instrument cluster. This is the blue plastic sheet that carries all the current tracks to the various instruments and lights. With time, these get corroded and/or damaged and don't make proper contact any more. Once you do this, you'll probably find the voltmeter works correctly. In the mean time, if you pull the pod and the gauge cluster, you can use a white pencil eraser to clean the contacts.

The gauges are there primarily to give trend information, they aren't very precise. What this means is that if your car always runs fine at 12.8 volts....but one day suddenly it indicates 16....then you know that something is wrong and you should investigate. As stated above...you could just pop the needle off and glue it back a little higher~

Good luck-

N

[JhwShark]

Originally Posted by Normy

First of all, are you reading the voltage at the battery? 12.8 volts is about correct...engine off.

Engine ON it should be 13.7....

-You need to replace the "foil" electronics on the back of the instrument cluster. This is the blue plastic sheet that carries all the current tracks to the various instruments and lights. With time, these get corroded and/or damaged and don't make proper contact any more. Once you do this, you'll probably find the voltmeter works correctly. In the mean time, if you pull the pod and the gauge cluster, you can use a white pencil eraser to clean the contacts.

Another reason I want to get it reading properly is that since it reads low it trips the warning light when the system get pretty loaded with stuff on.

The gauges are there primarily to give trend information, they aren't very precise. What this means is that if your car always runs fine at 12.8 volts....but one day suddenly it indicates 16....then you know that something is wrong and you should investigate. As stated above...you could just pop the needle off and glue it back a little higher~

Good luck-

N

Thanks for the input: all good.

12.8v off 13.8v while ON at Bat and Jump post and at CE contacts at (30). I agree with cleaning the foil contacts with the eraser on the cluster connections, that was my next step along with the connector.

I am resisting relocating the needle just because it will not be in proper position at OFF...my anal'ness. And since the gauge does behave properly, droping when I put further equipment load on, I prefer to try to clean the trace-route. I know of other v gauges with the pot on the back of them, but when I replaced my odo gear I was disappointed mine was without.

I am just trying to keep this beast in as original shape as possible. No mod's just 85k miles and a bad Jensen stereo...

...With that in mind, anyone have a proper Blaupunkt from this era '79?