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Discussion Starter #1
Hi all,

So, I’m troubleshooting a no-op speedometer and fuel gauge. I have a couple of questions about further investigation.

The fuel gauge... It always shows empty (I have a full tank). I disconnected the wire at the sender and touched it to ground — the gauge pegs to full. So, I’m assuming that both the wire and the gauge are good. So, I pulled the sender. It’s likely that it is the problem. My question is... how do you bench test it with a multimeter? Yeah, I know — buy a new sender you cheap bast***d. I probably will, but I’m one of those gotta-know-for-sure-what-exactly-the-problem-is guys, so please humor me. ?

The speedometer... last week, I crawled under and disconnected the cable at the transmission case for investigation. The driven gear looks OK — no stripped or broken/chipped teeth. I can’t say for sure that it’s not the drive gear inside the case, so I’m assuming that it’s OK. So, I reconnected the cable at the transmission and turned my attention to the gauge. Today, I pulled the gauge from the instrument panel to take a look at the cable end — it looks OK (it isn’t rounded, nice square tip). I put the rear end on jack stands, started the car, and put it in gear. The rotation of the tip was really sluggish and intermittently stopped altogether. I don’t think the cable is broken. My question is... is the sluggishness caused by crud inside the cable housing, or can it be that the drive gear inside the tranny is the culprit...?
 

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But Mad North-Northwest
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On the fuel sender, set your multimeter to measure Ohms. Attach one probe to the terminal to the fuel gauge, attach the other to the metal mounting flange of the sender. Move the arm up and down, you should see it vary from ~0 Ohms full to probably 120-240 Ohms empty depending on which particular setup you have.
 

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Fuel sender — put on the bench and measure resistance between the metal housing and the terminal. My guess is the wiper on the wire-wound resistor is not making contact and is an open circuit. You might be able to bend it into contact — but the actual winding might also be broken.

speedo- 90% sure it’s your cable. To test, remove the cable from the trans like you did, and spin the internal cable with an electric drill: see if the speedo gauge registers. If it’s anything in thesender drive. Sometimes the square female end gets rounded off and the cable doesn’t turn.
 

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But Mad North-Northwest
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A note: be sure not to spin the cable backwards or you can damage the speedo.
 

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Re spinning backwards, perhaps true but I'm not certain about that.
 

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But Mad North-Northwest
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You know, you're right, I'm thinking of the tach. The speedo would get turned backwards when you're driving in reverse.
 

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Tach can also be turned backwards without damage; same design as speedo.
 

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Discussion Starter #8
For everyone’s amusement, this is what the sender looked like and how much rust I scraped off. ?

1624506
1624507
 
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