No Speedometer/Odometer

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Va6622

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I have a 1989 Silverado . It was built in late '88 but sold as an '89. Its an automatic with a 5.7 350 engine. No 4WD. I left to go to work one day last week and noticed that my speedometer and odometer (analog) were not working. I tried to research the problem and replaced the vehicle speed sensor. No luck. I am almost certain that I do not have a speedometer cable. There is a 15 amp fuse labeled "brake" that also says speedo. I checked the fuse and it is good. I took a volt meter and checked for voltage at that fuse location and when I turn the key to on I get current at the fuse. All of the other gauges work. I notice that before I turn the key to start the truck I see the a little bit of the orange needle on the speedometer dial like all of the other guages, but as soon as I turn the key to on, the orange needle disappears on the speedo. I have the instrument panel out and was wondering if there was any way to test the electric motor behind the speedometer. Any help would be greatly appreciated.
 

DonYukon

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the stepper motor could have definitely failed. it is 30+ years old after all. IS the connection behind the dash ok?
 

someotherguy

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Those "moonie" clusters (used in 1988-1991) are somewhat known for speedometer failure. The signal from the speed sensor feeds into a buffer circuit built into the cluster. I believe the common problem is likely as simple as failed solder joints, which may not be readily visible without magnification. I say this because I know a few people that have beat cracks into their dashboards whacking them to get the speedometer working again; this tells me it's a connection issue, and that is probably due to the solder joints in the cluster.

If you're handy at all with electronics soldering work you could pop the cluster out and give it a good look-over with a magnifying glass and touch up any joints that look suspect. A shot of DeOxit spray in the connector socket would be a good idea, too.

I'd say you could just hunt for a replacement cluster but you're limited to 1988-1990 for a drop-in replacement, it could also have the same problem, and you'd likely need to recalibrate the cluster for the speedometer to be accurate as the settings are done in the cluster at the factory based on axle ratio and tire size.

Richard
 

DerekTheGreat

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What SoG said. You can check to see if the speedometer signal is getting to the cluster and the ECM too. The signal goes from the trans to the cluster and to the ECM. So if the scanner shows your speed but the cluster doesn't, the cluster has issues.

I had an '88 without a working speedometer, before I bought a scan tool. I replaced the speed sensor and had the cluster rebuilt, still no speedometer. Turned out that same fuse you checked had a bad socket. Fixed that mess up, working speedometer.
 

PlayingWithTBI

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About 8 years ago I had similar issues with my 88. 1st the odometer quit working, then the fuel gauge would show 1/4 tank when full. Finally the water temp gauge quit. I said screw it and bought this - still going great plus, I have a tach too :waytogo:

 

Va6622

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Back to square one. I noticed that when I replaced the vehicle speed sensor, I was getting a whining sound as I started moving. From the drivers seat it sounded like it was coming from the drivers side about half way back . I thought it was too much of a coincidence because I didn't hear the noise until I changed the sensor. I thought maybe it was because I bought a brand I never heard of so today I put a ACDelco sensor in. It still makes the same noise. It keeps pace with the speed of the truck. The faster I move, the faster the noise. I plugged in the instrument panel without the cover and as I was backing up I could see the speedometer needle moving . I shifted into drive and the speedometer started working. I pulled in the driveway and checked the tranny fluid then turned the truck off. When I turned the truck back on I could not get the speedometer to work again. Wouldn't the fact that it worked for awhile mean that the stepper motor is working?
 

Ruff Idol

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I noticed that when I replaced the vehicle speed sensor, I was getting a whining sound as I started moving. From the drivers seat it sounded like it was coming from the drivers side about half way back . I thought it was too much of a coincidence because I didn't hear the noise until I changed the sensor. I thought maybe it was because I bought a brand I never heard of so today I put a ACDelco sensor in. It still makes the same noise.
To my knowledge there is a manufacturing defect in nearly all the new replacement speed sensors you can get for these trucks. Something with the magnet on the end that tracks the speed - I've heard of someone having to file it down a bit because it was hitting the spinning tailshaft of the trans ever so slightly to make the noise!
 
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