Trouble with Yellow Box Speedo Calibration Box

[rsiwicki]

I am having problems with the yellow box speedo calibration to correct my speedo for the 4.08 rearend.

I have it wired up and it works fine until I get over 25+mph and then it goes dead....well the speedo stops working and just says "zero". As soon as I slow down under 25mph the speedo works again. I have run all the tests and everything appears to be operating correctly except for the test that you can set the box to output a constant signal while in park to test the output function and it is suppose to register something between 5~100mph when I do this test as the pulse register differently between cars.

When I swap out the little calibration box for the bypass wire that totally bypasses the box and just makes a continuous loop the speedo works fine all the way up...100+mph although the speedo is not correct.

I would think that if I had a loose/bad connection that when I install the bypass wire that my speedo would not work, but it works fine. Does anybody know why the speedo would work till 25mph and then all of a sudden go dead?

Wes has a video clip that I am waiting to be hosted so I can link you all to it so you can see for yourself what it going on.

Here is a link to the box.....

http://www.blackrobotics.com/yb_home.htm

EDITED: Here's the link.. http://www.q45.org/rob/speedo.asf

[Q45tech]

Well it seems to quit counting input frequency? Waveform shape or level from speed sensor, bad unit, or ripple on the +12 vdc power line or excessive load on output...............as the frequency rises any capacitors to ground in speedometer head [the isolation IC] acts as ever decreasing resistances to ground.

What does manufacturer say?.....................add 0.1mf non polarized capacitor or variable resistor in series with speed sensor line and output.

Without viewing pulse waveforms hard to diagnose.........someone with a function generator and counter should be able to better test unit.

[rsiwicki]

thanks for the reply Dennis.....

Unfortunately no reply yet back from the manufacturer and I emailed them the video clip as well. They have always been very good and quick to respond to my previous emails so hopefully I should get a response back soon. Either way…the car should be at T3 for the NOPI meet in Sept for some TLC and maybe we can revisit this if it is not resolved by then.

I ran one of the input test that blinks a red LED faster and faster as the wheel spins faster and faster and after 30mph I got a solid red light I think from it blinking so fast so I think the signal the yellow box is receiving is okay.

The only test that did not work is the output test where the black box will send a constant pulse signal while in park to the speedo so show that the output connection is okay. When I ran this test I did it in both park, nuetral, and drive (with brake on) and the speedo just registered "zero".

It is strange how the speedo works perfectly when I install the bypass wire that totally removes the black box altogether.

I think the input side is okay, but I think there is some conflict going on with how the Q45's speedo interpets the output signal from the yellow box versus just straight from the OEM speed sensor?

[Q45tech]

Thats what I said -----waveform distortions [shape rise/fall time squarewave vs sine -quasi sine]. Need a scope to look.

[rsiwicki]

Sorry for the misunderstanding on output vs. input error reading.

Still no answer yet from the "yellow box" company in Australia. I emailed them Sunday, Monday, and Tuesday evening so they receive the emails first thing in the moring the next day. I emailed basically what I wrote above and also a video clip of the speedo. I have no idea why they have not responded yet...they were very good in answering questions, confirming my order, and sending the product asap. Maybe it is some holiday in Australia right now. I will post their response as soon as I receive it.

[jamesmost]

Robif u do not get a return call use another # and first inquire about a bulk purchase they are sure to call back

[rsiwicki]

Dennis....here is their response and I think what they said might be a solution. When I ran the input test the red LED light is suppose to blink faster and faster as the vehicle moves faster and faster, but you are suppose to be able to always distinguish the blinks versus a constant LED. This test works when going 5mph as the light blinks fast, but when I hit about 10mph or more the light turned into a solid red light that did not blink anymore so maybe the input signal is too fast for the yellow box.

Hi Robert,

Sorry for the delay in responding.

It sounds like your signal is too fast for the 2-wire YB. Usually 2-wire sensors send a much slower output.

Could your sensor be a 3-wire sensor with the sensor body being grounded to the chassis? This is a very unusual configuration but it may be possible.

You will probably need a faster YB to handle the signal output. I shall send you out a 3-wire Yellow Box for you to try. If the 3-wire YB does not work then your sensor is probably not compatible.

Could you email through your shipping address and I shall send the new YB out tomorrow. You keep your YB until we can test both.

Thanks -Jennifer

[rsiwicki]

I received and tried the other yellow box model designed for motorcycles that is suppose to have a faster pulse response similar to what is found on motorcycles....but no good. This time it did not even work at all.

open to suggestions....right now I am getting use to reading my speedo at 13.25% higher however it has slowed down my driving habits somewhat which is probably a good thing.

[97Q45t]

You could try the Digital Speedo Corrector from AutoSpeed.com. It's cheaper than the Yellow Box but it comes in parts. You'll need to assemble the kit.

http://www.autospeed.com/shop/....html

[rsiwicki]

thanks for the info....but I was not hoping to spend any more monies on this type of thing. The car probably will be in Atlanta for NOPI and I will have T3 look at it to see what the heck is going on with the speedo box. I have checked all the connections and functions and all seems good except that it does not work over 25mph.

[elwesso]

did you by any chance try switching the wires or something???

Why dont you just install the 4.08 speedo sensor from the Z32.

[rsiwicki]

Wires are all in good order....The 4.08 speedo gear is too fat!!! but I am seriously thinking about going and buying two of them and experimenting cutting down the speedo gear to the exact diameter of the Q's gear then it will work. I know AGM's mechanic fabricated a special speedo gear to work and I think with enough time I could do the same cutting the nylon/plastic gear down to size.