Gary Lewis Posted November 11, 2021 Share Posted November 11, 2021 Fair enough. The only other thing that comes to mind is the needle got moved on the shaft somehow... botched gauge restoration? That's very possible. Link to comment Share on other sites More sharing options...
ratdude747 Posted November 11, 2021 Share Posted November 11, 2021 Fair enough. The only other thing that comes to mind is the needle got moved on the shaft somehow... botched gauge restoration? That's very possible. *Puts on Electrical Engineer hat* I was thinking maybe a bad connection, but as tachometers (in terms of the wiring to the cluster) are frequency driven rather than voltage/current level driven, I'd think such would result in erratic readings or no reading. Technically there could be a fault in the cluster's circuit board (I don't recall if there's any circuitry between the tach input and the gauge itself)... but otherwise, I'd lean towards a poorly zeroed needle if the shift is consistent at multiple values (fast idle, normal idle, etc.). If not, possibly a faulty gauge (or cluster if there is circuitry on such). *Takes off Electrical Engineer hat* Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 11, 2021 Share Posted November 11, 2021 *Puts on Electrical Engineer hat* I was thinking maybe a bad connection, but as tachometers (in terms of the wiring to the cluster) are frequency driven rather than voltage/current level driven, I'd think such would result in erratic readings or no reading. Technically there could be a fault in the cluster's circuit board (I don't recall if there's any circuitry between the tach input and the gauge itself)... but otherwise, I'd lean towards a poorly zeroed needle if the shift is consistent at multiple values (fast idle, normal idle, etc.). If not, possibly a faulty gauge (or cluster if there is circuitry on such). *Takes off Electrical Engineer hat* The wire I'm talking about is just the ground that tells the tach to go into 8-cylinder mode. So I'd think it was either in 6 or 8 mode. But I think you are onto something about the needle. If it is consistently 500 R's off then it isn't that ground. In fact, it is hard to imagine what it could be other than the needle being offset. I've pulled the needles off tachs and put them back in, and it can be done fairly easily. I think I'd note where it is, pull it off, and put it back on 500 R's higher. Link to comment Share on other sites More sharing options...
Dipstik86 Posted November 11, 2021 Author Share Posted November 11, 2021 The wire I'm talking about is just the ground that tells the tach to go into 8-cylinder mode. So I'd think it was either in 6 or 8 mode. But I think you are onto something about the needle. If it is consistently 500 R's off then it isn't that ground. In fact, it is hard to imagine what it could be other than the needle being offset. I've pulled the needles off tachs and put them back in, and it can be done fairly easily. I think I'd note where it is, pull it off, and put it back on 500 R's higher. Now just to throw this into the mix, the truck has a DUI HEI distributor on it. Would that be the cause of the incorrect readings? Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 11, 2021 Share Posted November 11, 2021 Now just to throw this into the mix, the truck has a DUI HEI distributor on it. Would that be the cause of the incorrect readings? I doubt it. Usually it either works or doesn't. But I can't imagine it would subtract 500 R's. I'm staying with the needle being on wrong. Link to comment Share on other sites More sharing options...
Dipstik86 Posted November 11, 2021 Author Share Posted November 11, 2021 I doubt it. Usually it either works or doesn't. But I can't imagine it would subtract 500 R's. I'm staying with the needle being on wrong. Well I popped the cover off the dash and attempted to move the needle. Not sure what was holding it on but I didn't even get a chance to grab it and it just fell off. There is like a black portion of the needle that holds it to the pin and that was mostly broken off. I'm attempting to epoxy the needle back in place so we'll see if that was the issue the whole time. Now the question is, do I set it to 0 with the engine off or below 0? Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 11, 2021 Share Posted November 11, 2021 Well I popped the cover off the dash and attempted to move the needle. Not sure what was holding it on but I didn't even get a chance to grab it and it just fell off. There is like a black portion of the needle that holds it to the pin and that was mostly broken off. I'm attempting to epoxy the needle back in place so we'll see if that was the issue the whole time. Now the question is, do I set it to 0 with the engine off or below 0? Mine points at 0 with the engine off. I can't say it is perfect, but it seems to be about right. Link to comment Share on other sites More sharing options...
Dipstik86 Posted November 11, 2021 Author Share Posted November 11, 2021 Mine points at 0 with the engine off. I can't say it is perfect, but it seems to be about right. Well I ended up having to make a new needle out of an old speedo needle cut down and with a shortened stem to fit properly. Seems to be accurate now when compared to the aftermarket tachs. Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 11, 2021 Share Posted November 11, 2021 Well I ended up having to make a new needle out of an old speedo needle cut down and with a shortened stem to fit properly. Seems to be accurate now when compared to the aftermarket tachs. Link to comment Share on other sites More sharing options...
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