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10-03-2008, 12:47 PM
| | |  Speedometer not working
I have a 1982 CJ7..... My speedometer, temperature gauge, and gas gauge (all one unit) doesn't work. Does anybody know what could be the cause? Do I need to replace the entire unit or is it something simple?
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10-03-2008, 02:03 PM
|  | Moderator | | Join Date: Dec 2001 Location: Belleville, Illinois
Posts: 9,619
| |
Welcome to the board, Dan!
The temperature gauge and gas gauge are electrical. They both get power from the ignition switch and pass it through the gauges to the sending units which provide variable resistance to ground. There's a voltage regulator built into the gauge cluster to provide a constant voltage to the gauges. Your problem is most likely lack of power from the ignition circuit, or a bad regulator.
Board member John Strenk has put up a very good write-up on troubleshooting CJ instruments. If you do a search for "John Strenk's troubleshoot" you should find it.
The speedometer is a different fettle of kish. It's purely mechanical. There's a plastic gear in the transmission that drives a flexible cable that spins the speedometer input. Inside the speedo the cable spins a magnet inside a copper cup attached to the needle. There's a slight bit of drag imparted to the cup, which is resisted by a spring. That's all there is to it.
Disconnect the cable at the speedometer and let the end hang out. Then go for a drive. Chances are that the cable won't be turning. You can pull it out of the jacket, and will probably fuind that it's broken. Replacements are available at a parts house. If it's not broken, the driven gear in the transmission might be stripped. That requires removing the drive adapter from the transmission. There's just a small bolt and clamp holding it in.
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EVERYTHING's easy for the guy who doesn't have to do it. B. Dash Fabrication |
10-08-2008, 12:31 PM
| | Moderator | | Join Date: Dec 2001 Location: Belleville, Illinois
Posts: 9,619
| |
You need to pull the cable out of the sheath and confirm that it's broken - the plastic driven gear could be stripped, although it's not likely. If it's broken you'll have to disconnect the sheath at the other end to get that piece out.
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EVERYTHING's easy for the guy who doesn't have to do it. B. Dash Fabrication |
10-08-2008, 08:54 PM
|  | Keyboard Implanted | | Join Date: Jan 2004 Location: Indiana
Posts: 3,725
| |
Exactly... Except the speedo cable goes into the tail shaft of the transfercase, D300 on a 1982 CJ.
John Strenk's pages don't come up tonight... I'll link them for you if/when they show up again. 
Dale
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