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08-14-2010 #1Registered User
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- Aug 2007
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- 156
classic instruments - calibrating speedometer??
Ok, I have all my gauges working except for my speedometer gauge. The car is a 93 Camaro with an LS1/TH400 swap. My gauges are Classic Instruments gauges.
I have the TH400 reluctor wheel/pigtail conversion; here are the part numbers I'm using:
12085498 - pigtail connector
8655315 - reluctor
24232618 - sensor
I'm having a very difficult time calibrating the speedo.
The instructions say to first identify the type of gauge I'm using by looking at the back of the gauge. Apparently, I'm using a 4 5/8" 16-PULSE speedometer. Here's what the back of it looks like:
Classic Instruments told me I needed to use an SN74 box, and wire it like this:
And that is EXACTLY how I have it wired up. On my LS1 engine harness, I have the green/white wire labeled VSS OUTPUT as my ECM Computer Speed Signal wire in the diagram. So that goes to the INPUT spot on the SN74 box. My grounds are good, the SN74 and the speedo are both getting power. So then after it's all wired up, here is the calibration process (short read): http://www.classicinstruments.com/Us...alibration.pdf
Unfortunately, when I get to 60mph using a speedometer app on my phone, hold the SN74 pushbutton down to get into Real Time calibration mode, and then click the pushbutton again, THE NEEDLE DOESN'T MOVE. I mean it doesn't move AT ALL.
Has anyone ever had experience with a Classic Instruments speedometer and an SN74 box??
I know this post is a little long but I'm not sure where to go from here. I'd call Classic's tech line, but that's the same line that told me to get the SN74 and it's not working. They're also closed on weekend which is when I have time to work on my car.
I'm so close!! One last gauge to go; thanks to anyone willing to help me out at all!
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08-15-2010 #2Registered User- Join Date
- Aug 2007
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- 156
Ok, what I did just now was I took the VSS OUTPUT wire out of the Input spot on the SN74, and took the wire out of the Output spot on the SN74, and connected those two wires together. So the VSS OUTPUT wire is now directly wired to the #3 terminal on the back of my speedometer, the signal terminal.
Took it out for a drive at 60mph, and the needle DID NOT move. Brought it home, checked voltage with a multimeter at the power and ground terminals on my speedometer, and I'm getting 12.25 volts, so I know the gauge is getting power.
Anyone have any ideas?
08-15-2010 #3Is the wire good from the speed sensor to the ECM computer?
08-15-2010 #4Registered User- Join Date
- Aug 2007
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- 156
08-15-2010 #5This one is 207$, cheapest I know of: http://www.picotech.com/handheld-oscilloscope.html it uses a laptop.
Have you checked continuity of the wire at least?
08-15-2010 #6Registered User- Join Date
- Aug 2007
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- 156
A friend of mine had a Cyberdyne digital gauge sitting in his garage. I wired the + and -, and connected the gauge's signal wire to the vehicle output wire from the pcm. Then I went for a drive.
The gauge the entire time read 0mph. So I don't think I'm getting a signal from the PCM at all. I will try to retrace the wires from the VSS on the transmission; I think that's a good place to start.
08-16-2010 #7