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Posted By: oldpar 1979 dodge b200 instrument panel circuit board question - February 04th 2018 12:19 am
My instrument panel never did seem to work right.
the ammeter never seemed to register any movement.
The oil light never came on ( I added an oil pressure guage years ago).
Fuel guage never seemed to read correctly.
Lately speedometer started to pin whenever I went over 70MPH
So I decided to tear it open and resolve all this.

New speedo cable turns out to be wrong one. ordered 1979 to 1984. Looks like from pics I have seen 1985 or later.

circuit board looked as though it had been repaired......New circuit boards (both)

new voltage limiter (solid state)

My question is:
When assembling new circuit board there is a lug at one end near one of the IP lights.
Is this a ground lug ? no wires were attached to it but there is a connector nearby that looks as though it would fit (doesn't quite reach) but that may be the instrument panel could have been changed.
Pics attached :

Attached picture IMAG1207.jpg
Attached picture IMAG1208.jpg
Posted By: Reed Re: 1979 dodge b200 instrument panel circuit board question - February 04th 2018 12:56 am
Originally Posted by oldpar
My instrument panel never did seem to work right.
the ammeter never seemed to register any movement.


That might be normal if you never put a large load on the alternator. If the alternator was putting out enough energy to keep the battery charged then the ammeter on the dasy would move very little, if at all.

Originally Posted by oldpar
The oil light never came on ( I added an oil pressure guage years ago).


This is a good thing. I ideal circumstances the oil light only comes on when you first turn the key on. As soon as the motor starts it should build enough pressure to turn the light of.

Originally Posted by oldpar
Fuel guage never seemed to read correctly.


Not overly surprising. Clean the grounds, you already replaced the circuit board voltage regulator, last step is to get ohm readings of the sending unit at various float levels.

Originally Posted by oldpar
Lately speedometer started to pin whenever I went over 70MPH


Sounds like you need to rebuild the speedometer head.

Originally Posted by oldpar
So I decided to tear it open and resolve all this.

New speedo cable turns out to be wrong one. ordered 1979 to 1984. Looks like from pics I have seen 1985 or later.

circuit board looked as though it had been repaired......New circuit boards (both)

new voltage limiter (solid state)

My question is:
When assembling new circuit board there is a lug at one end near one of the IP lights.
Is this a ground lug ? no wires were attached to it but there is a connector nearby that looks as though it would fit (doesn't quite reach) but that may be the instrument panel could have been changed.
Pics attached :


Your pictures are too small and of too low of resolution to let me see what you are referring to. Try posting bigger pictures.

If memory serves, there is one large plug that goes to the circuit board by the speedometer and a separate smaller plug for the oil pressure and battery gauges. i do not recall any separate large lug or plug on the 79-87(?) instrument cluster circuit board.
Originally Posted by Reed
Originally Posted by oldpar
My instrument panel never did seem to work right.
the ammeter never seemed to register any movement.


Thank you for the Quick response !!
I will try larger photos.

That might be normal if you never put a large load on the alternator. If the alternator was putting out enough energy to keep the battery charged then the ammeter on the dasy would move very little, if at all.

Even with low battery and I know charging heavily No guage movement.

Originally Posted by oldpar
The oil light never came on ( I added an oil pressure guage years ago).


This is a good thing. I ideal circumstances the oil light only comes on when you first turn the key on. As soon as the motor starts it should build enough pressure to turn the light of.

Even with low oil pressure the oil pressure gauge has shown still no light.

Originally Posted by oldpar
Fuel guage never seemed to read correctly.


Not overly surprising. Clean the grounds, you already replaced the circuit board voltage regulator, last step is to get ohm readings of the sending unit at various float levels.

New grounds, new fuel sending unit. still flaky, this and new speedo actin is what prompted me to look at instrument panel.
Originally Posted by oldpar
Lately speedometer started to pin whenever I went over 70MPH


Sounds like you need to rebuild the speedometer head.

I hope not, But have a suspicion you are correct. This is a new problem. I thought to try the easiest thing first.

Originally Posted by oldpar
So I decided to tear it open and resolve all this.

New speedo cable turns out to be wrong one. ordered 1979 to 1984. Looks like from pics I have seen 1985 or later.

circuit board looked as though it had been repaired......New circuit boards (both)

new voltage limiter (solid state)

My question is:
When assembling new circuit board there is a lug at one end near one of the IP lights.
Is this a ground lug ? no wires were attached to it but there is a connector nearby that looks as though it would fit (doesn't quite reach) but that may be the instrument panel could have been changed.
Pics attached :


Your pictures are too small and of too low of resolution to let me see what you are referring to. Try posting bigger pictures.

If memory serves, there is one large plug that goes to the circuit board by the speedometer and a separate smaller plug for the oil pressure and battery gauges. i do not recall any separate large lug or plug on the 79-87(?) instrument cluster circuit board.

New photos attached

Attached picture IMAG1207.jpg
Attached picture IMAG1208.jpg
Posted By: oldpar Re: 1979 dodge b200 instrument panel circuit board question - February 04th 2018 11:14 pm
checked things with ohm meter today.
The black plug not a ground.
The board gets ground from pin A on round plug, I guess the lug is just extraneous.
I put the instrument panel together today, just ignoring the lug.
All the gauges worked including the ammeter and fuel gauge seems accurate.
I have a 36 gal tank that was reading 1/4 after re installing the new boards so figured if i put in 9 gals I should read 1/2 tank.
Sure enough 1/2 tank right on the money. My temp gauge reads dead center normal it had been reding low up to this point.
The oil warning lamp lit until I started it then went out just like it should.

I don't know if the new board or new voltage limiter fixed it. but it is all good now !
Oldpar, I was actually just looking for info on this sort of thing and if you've got a minute, maybe you can help me out. I've got an '86 B250 and I'm having a heck of a time finding the correct speedo cable and speed sensor (mine was cut out when I bought it for some reason). Instead of searching for another week or so, I am curious if a newer, digital speedo would fit into my dash (like the early 90 speedo's) at which point I'll just swap to a new style sensor. I have a '93 B250 that I can snag parts from, which is why I'm asking. I just thought that if you were having issues with your speedo, maybe you had thought about swapping it out with a new one at some point and had already found the answer. If not, no problem. Your van is awesome!
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