Hi guys. I have a problem with the speedo in my 86 TA. The car is equipped with a 305 with a 4 bbl Rochester and a T5 tranny. Now how the problem came up was actually probably done by yours truely. I wasn't sure what a switch was for on the dash but now I figured out that it is for a factory amp for the sound system. To make a long story short, earlier this week, I replaced the factory stereo with an aftermarket CD deck because the factory unit was dead.
Now getting back to the dash switch, I hit the switch while my stereo was playing. Suddenly, my speakers emitted a big "burp", the power antenna re-tracted itself back into the fender, and when I went for a drive later, the speedo was dead! But the CD player and speakers still work fine... GO Figure!
Because of my stupidity, my power antenna won't work and the speedo is out. I already went through the fuse panel with my tester light and checked every fuse myself. Everything is OK. So what am I overlooking? Any insight would be much appreciated...

 

Is your speedometer electrically or mechanically driven? Assuming its mechanical driven as i believe it should have been ide say you have a broken or disconnected speedometer cable. With no power it should always work if its mechanical. If its electric thats a different story but i believe in 86 they were mechanical.

 

IIRC, 'Birds were mechanical 82-85 and electric thereafter. One way or another, unless coincidence was at play where the speedo is concerned, the problem "sounds" as if something was fried. The antenna relay and speedo buffer are on the same side of the car. You might take a peek/sniff at them.

JamesC

 

add signatureBy saying speedo buffer & antenna relay, do you mean the speedo buffer is a VSS? I have seen something on another thread about a VSS. I assume that stands for Vehicle Speed Sensor?... I could be wrong...
Yesterday I was "sniffing" around on the passenger side of my car. I removed the lower dash panel and found 2 "boxes" behind the panel. I assume that one of these could be the speedo buffer that you are talking about. One was a metal box with a harness running into it, and the other one was a black plastic box with a harness running into it. The black box also had "Delco" on it. Am I on the right track? BTW, I also found a yellow box under the dash in the same area but I already figure that it is for the HEI ignition, an ignition signal amplifier (it had "made in England" stamped on it)...
Sorry about all these "made in.." & "Delco" stamp references, I'm new to this game with these 3rd gen F bodies... (damn! My 76 Ventura was SO much easier to diagnose & work on...lol)
Thank you in advance for getting back to me about this problem.

 

An electric speedo would have a VSS mounted on the tail shaft of the trans and, IIRC, a yellow buffer box on the pass side. Located in that area as well are the cruise control module (black) and the ECM (metal box). The antenna relay is also found in that general area.

JamesC

 

Thank you, JamesC... I will take a look at these componets tomorrow in my TA. So the Yellow box is a buffer for the speedo... I shall check everything over tomorrow and I'll keep you updated on "Gina's" progress.
Thank you... gotta go, I think my dinner is about to burn... LOL
Take care...

 

Update to you, JamesC... today, I was "sniffing" around the Buffer box for the speedo with my tester light. I confirmed that there is power going to this box with my tester (grounded) by the 1 red wire in the harness. Now, an interesting thing is that there also is a green wire (coded "C" on the plug) that goes into the box. when I touched the tester to this green wire, the speedo needle kept jumping up towards 35 mph and back down to zero over and over, which also tripped over the odometer a few times. What is going on here? Do I have a bad ground in the buffer box? Or is it just a sign that the buffer box is shot? Any theories or recommendations on this "phenomenon" that I have stumbled across would be muchly appreciated...
BTW, the antenna relay I have also found. When I replaced the inline fuse on my deck (for the power antenna wire), the relay now clicks on & off whenever I power up and shut off the CD player... at least I am getting somewhere (I think...)

As I said before, thank you sir, for your help...

 

Check the following thread, especially post #6:

https://www.thirdgen.org/forums/elec...s-wireing.html

You might confirm that you have purple and yellow wiring coming off the tail shaft of the trans.

JamesC

 

Hey JamesC! I have an update for you... I finally got my speedometer working! It turns out that the Yellow and Purple wires that run down to the VSS on the side of the transmission was at fault. What happened was whoever worked on my car before hand was working on another electrical problem and did a half baked job on it (it had to do with the Alternator wiring) When they did this, the wiring loom was not properly re-installed, resulting in the wires to touch the pass. side exhaust manifold, thus resulting in the VSS wires burning all the way through!

Now that I replaced the wires, she is working again.
Thank you to everyone who contributed on suggestions for tracking down this problem!