Intermittent speedometer does not work

Tiny
BOB%
  • MEMBER
  • 1985 CHEVROLET CORVETTE
  • 5.7L
  • V8
  • 2WD
  • MANUAL
  • 120,000 MILES
My car listed above (4+3)transmission has a problem with the speedometer. It works sometimes and doesn't most of the time. It has the digital dash (which lights up sometimes)and that is iffy too. What would cause the speedometer to work sometimes and then stop? BOB
Monday, May 4th, 2020 AT 1:51 PM

8 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Just to clarify, is the speedometer the only thing that doesn't work at times? Also, when the speedometer is not working do the lights not work at the same time? In other words, do the speedometer and lights work at the same time and not work at the same time or different?

I attached the info for the speedometer but depending on the answers to this it may not be the cable or housing issue and the lights may be a different issue.

Let me know and we can go from there. Thanks
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Monday, May 4th, 2020 AT 5:40 PM
Tiny
BOB%
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My dash is a digital dash and therefore I don't think there is a cable. Also, the lights and the speedometer occur at different times. It's frustrating not knowing how fast you're going.I really appreciate this site and you guys are the best. Thank you, BOB.
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Monday, May 4th, 2020 AT 9:41 PM
Tiny
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You are correct. However the idea is the same. Take a look at the tail shaft pictures attached, to see if the driven gear has an electrical connector on it. If it does then the gear is driven by the output shaft and this PM generator sends a signal to the cluster that translates that into a MPH reading. I would check for voltage coming out of that gear and if you have it then we need to go to the back of the cluster and see if the signal is getting there. The fact that it is intermittent it may just be a connector issue at the gear or the cluster. The lighting on the cluster may indicate an issue at the cluster but this is where we need to start.
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+1
Tuesday, May 5th, 2020 AT 6:55 PM
Tiny
BOB%
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  • 70 POSTS
I will check and see if there is a connection on the tail shaft. Thank you for the info. BOB.
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Tuesday, May 5th, 2020 AT 8:33 PM
Tiny
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You are welcome. Please let us know what you find. We will be here if you need more info or help with this one. Thanks
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Wednesday, May 6th, 2020 AT 6:01 PM
Tiny
BOB%
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  • 70 POSTS
I haven't had a chance to jack the car up and look yet.I will let you know what I find out. Thank you for all your excellent info. BOB
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Wednesday, May 6th, 2020 AT 9:38 PM
Tiny
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No problem. We will wait to hear back from you whenever you get to it.
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Thursday, May 7th, 2020 AT 6:43 PM
Tiny
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Thank you, BOB.
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Thursday, May 7th, 2020 AT 8:59 PM

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