Speedo Issues

[Texcuda]

My speedo just started reading 10 mph high.

Now, please keep in mind, my truck is not stock, nor does it have any of the factory speedo wiring. No DRAC, No VSSB, etc.....

My truck has the TCI EZ-TCU running the factory speedometer. This issue cropped up when I switched from the 93 speedo only cluster to a 93-94 speedo/tach cluster. The speedo only cluster worked fine for 2 years, I just wanted the tach. I installed the speedo/tach cluster a week ago, and everything was working fine until this morning when the speedo pegged at 85 while cruising at around 80 mph, and from that point, has been 10 mph high. I used a GPS speedo app, and the TCI handheld to verify the TCU is outputting the correct speed, ie: speedo reads 75, GPS/handheld read 65, etc.

The issue has to be in the speedo itself. Does anyone have info specific to the speedo itself? I read on an older post there is a circuit board in the speedo. Finding the speedo/tach clusters is painful at best, and I would prefer to fix the cluster I have rather than spend more money for an unknown cluster.

 

[DerekTheGreat]

All I can tell you is that while the internals of the clusters may be the same, the '94 cluster is different in that the oil pressure gage reads "0, 40, 80" whereas the the earlier ones read "0, 30, 60".

 

[Texcuda]

I'm going to put the non-tach cluster back in to verify the issue indeed speedo, and not something else. Perhaps someone will know if the circuit board inside the cluster and/or the stepper motors can be swapped between the clusters.

 

[885speed]

My speedo just started reading 10 mph high.

Now, please keep in mind, my truck is not stock, nor does it have any of the factory speedo wiring. No DRAC, No VSSB, etc.....

My truck has the TCI EZ-TCU running the factory speedometer. This issue cropped up when I switched from the 93 speedo only cluster to a 93-94 speedo/tach cluster. The speedo only cluster worked fine for 2 years, I just wanted the tach. I installed the speedo/tach cluster a week ago, and everything was working fine until this morning when the speedo pegged at 85 while cruising at around 80 mph, and from that point, has been 10 mph high. I used a GPS speedo app, and the TCI handheld to verify the TCU is outputting the correct speed, ie: speedo reads 75, GPS/handheld read 65, etc.

The issue has to be in the speedo itself. Does anyone have info specific to the speedo itself? I read on an older post there is a circuit board in the speedo. Finding the speedo/tach clusters is painful at best, and I would prefer to fix the cluster I have rather than spend more money for an unknown cluster.

FWIW although you have a bit of a unique set up, all signs do point to the cluster...
The speedo in my '97 is also about 10MPH off(on the high side) so 65 on the cluster gives me 55 actual. Confirmed mine with PCM speed readout vs GPS as well.

I know for the newer style clusters like mine, dorman offers a reman unit, not sure about the older style. However since you have two clusters to swap between, personally I'd remove the one you want to keep in there and ship it out to a well known company to be repaired/tested. I could recommend using Model Electronics, I've worked at Nissan for years and that's who remans all Nissan clusters, as well as some other manufactures. Never had an issue with their work.

 

[Texcuda]

FWIW although you have a bit of a unique set up, all signs do point to the cluster...
The speedo in my '97 is also about 10MPH off(on the high side) so 65 on the cluster gives me 55 actual. Confirmed mine with PCM speed readout vs GPS as well.

I know for the newer style clusters like mine, dorman offers a reman unit, not sure about the older style. However since you have two clusters to swap between, personally I'd remove the one you want to keep in there and ship it out to a well known company to be repaired/tested. I could recommend using Model Electronics, I've worked at Nissan for years and that's who remans all Nissan clusters, as well as some other manufactures. Never had an issue with their work.

I'm gonna hit the junkyard this weekend and see if i cant grab some circuit boards and speedo motors out of several tach/speedo clusters (hopefully it'll be cheaper than paying for the whole cluster) to play with, swap between, etc. I'll look in Model Electronics tho. Thanks!

 

[Texcuda]

I didn't have time to change out the clusters, so I decided to track the odometer and trip meter and compare it to miles driven on my gps speedometer app. I reset all 3 in my driveway and drove to work. The results were:

Odometer: 29.3 miles
Trip: 29.2 miles
GPS: 29.51

Using the GM calibration, this resulted in an accuracy of 1.007 which is inside the GM spec of .96 - 1.04.

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Conclusion: it seems my speedometer was initially reading wrong by 10 mph, and self corrected earlier this week. I'll reset the needle and check it again in a couple of weeks.