On my 87 firebird v6 Automatic. I have been trying to diagnose whats up with my Speedometer.

Video of my speedometer issue



1/08/2011 problem found http://www.youtube.com/watch?v=veq_DSlMsss

My speedometer still resives power but most of the time now it does its own thing. It used to work fine. Everything in this car is stock. the front tires are a little bigger then factory, but still read correct for at least 6 months with these tires, rear tires I belive were stock size. The other gauges work fine and the trip and odometer work.


In trying to diagnose this, I discoverd the 87 bird does not use a cable.
I replaced the VSS in the end of my transmission a couple of times to no avail.

I am seeing that some use a Buffer box? and I see one listed in my wiring diagram. If I have one, can u point me in the direction to test it.

Is this my buffer box? vid of what could be my buffer box? (ended up being my cruise control module)
found the buffer box, Yellow box pickybacking on the ECM

Also been having a hard time figureing out what to look for in buying a new Speedometer Head. going to look at a speedo at oriellys tommorow. ( I do want to get a speedo that reads above 80/90 mph)

This is what my instrument cluster looks like
Speedometer out of cluster does the needle itself pull off?

Car is my daily driver, and up for inspection.
Any direction apreatiated

 

 

couple Places ive found for wiring diagrams so far

click and scroll down to see Wiaring diagrams posted by 87v6Bird

heres Autozones, believe have to login and possible search through repair guides

Believe I have these in my Chiltens as well.

Wires to 4 out buffer box
buffer box details < fills in the gaps for the buffer box

1 connector starting from bottom up had wire colors

Blk/white stripe
Green/ black stripe
Red
Brown
Pink/Blk

next connector
Yellow
Purple

A look inside my Buffer box at the board inside

 

Light green with black stripe to cluster

brown to ECM

pink/blk battery

blk/w ground

red cruise control module

seperate connector from VSS
yellow
purple

In manual for diag it says to test the light grn/blk to ground and with ignition on should see 12v at disconected connector that would connect to buffer box.
I do not get correct voltage reading here. Is it that the power goes into cluster, then through the circuit board on the cluster, power comes back through this light grn/blk wire to the buffer?


vid of my lt GRn/blk wire test. http://www.youtube.com/watch?v=B6KkBKw9x_M




I Just unplugged the battery positive and negative cables completly.
IGN off

Ohms meter set for continuity
Connector unplugged from buffer box. with and without instrument cluster installed.

Red Lead in buffer connector at Lght GRN/Blk from instrument panel
Black lead in buffer connector at Black/Wht Ground
Result: Continuity True
http://www.youtube.com/watch?v=2bIUGxLRf_w

Red Lead in buffer connector at Lght GRN/Blk from instrument panel
Black lead in buffer connector at pink/Blk 12V from battery through ign/fuse
Result: Continuity True

Red Lead in buffer connector at Pink/Blk 12V from battery
Black lead in buffer connector at Blk/Wht ground
Result: Continuity True

Red Lead in C1 connector at Cluster Lght GRN/Blk to Buffer Box
Black lead in buffer connector at pink/Blk 12V from battery through ign/fuse
Result Continuity True

Red Lead in C1 connector at Cluster Lght GRN/Blk to Buffer Box
Black lead in buffer connector at Light Grn/Blk from cluster
Result: Continuity FALSE http://www.youtube.com/watch?v=Icobegi0Vbc

Red Lead in buffer connector at Lght GRN/Blk to cluster (same result if replaced with power and ground for this example)
Black lead in buffer connector at Brown to ECM
Result: Continuity FALSE

Red Lead in buffer connector at Lght GRN/Blk to cluster (same result if replaced with power and ground for this example)
Black lead in buffer connector at Red to cruise control
Result: Continuity FALSE

 

Found the Issue WOOOOOOOOOO

http://www.youtube.com/watch?v=veq_DSlMsss

but yeah prolly the wiring harness at the cluster, rubbed cut its was through into the wires and grounding at the metal that was cutting through them looks like.

Another WOOOOO

Now to see if I can get closer and to figure how to repair them

 

I'm having a very similar problem..Speedo its jumping all over even in park. ok, might be onto something..I tested at the buffer between the black/white tracer(ground) and the Pink/black tracer(power) and got 12V which is correct. When I test between the black/white tracer(ground) and the Green(gauge cluster), I should also get 12V but only getting 10V.Then I disconnected the battery, tested the black/white tracer to ground and all good I have continuity..Here's where it gets funky, I tested the Pink/black tracer to ground and it ALSO showed continuity..So it's looking like the Pink/black tracer is shorting to ground correct?? If So where does that Pink/black tracer come from so I can try to find the short.

 

I was lucky enough to have TGO member Pocket send me over a VSS diagram. My cars an 89 and think his diagram was for a 92? Anyway from following the diagram the Pink/Black tracer runs from the VSS buffer to the Fuse Block... So I must have a short between those areas..Seem like I'm on the correct path? Does the 12V Pink/black tracer go anywhere before the fuse block or is it a homerun direct to the fuse block? The diagram I have isnt very detailed

 

bump