I wondered if any of you guys have had this problem:-

I replaced the tacho circuit board and when i turn on the ignition, the needle goes back to zero. When the car is started the needle still registers zero and doesn't move. If i then drive the car and kick down or rev the car hard the needle then jumps up and then goes of the scale and stays there until i kick down or rev engine hard.

I bypassed the supressor on the lead from the distributor, but still no good.

HELP!!! any ideas???

 

Check out this thread..
http://forums.corvetteforum.com/zerothread?id=595929

I'd contact Redline.. URL is in this other thread.. Good luck!

 

looked at above post but my problem is very similar to Andrew's on that thread and no one has offered a solution.

I have sent an email to Redline and await there response.

 

Try giving Redline a call.. They were really helpful on the phone.. Sorry I can't help any more.. My tach is off by 7K and I'm still trying to figure out if I want to mess with it or accept it.. :cheers:

 

Have called John at Redline, what a helpful guy!!! Will be using him for any instrument replacements from now on.

 

So, what did he say about your tach?

 

John said that he thinks that the board is faulty and i'm going to test the tach without the circuit board on and I will go from there.

 

Test the tach without the circuit board :skep: What will this show? Let me know if you find the answer. I am stumped.

PaulD, I thought that the board was bad as well. When the vendor sent me another one, I returned it as well. It did the same thing you are describing. Did you use Ecklers to get the board?


[Modified by Andrew, 12:15 PM 7/7/2003]

 

PaulD: One thing that I did was borrow a friends board from a 1980. His board made the tach move. After adjusting the needle, it started working. This was interesting since Ecklers claims that the 79 and 80 are different boards. I finally gave up on the project. Please let me know if you find an answer. :cheers:

 

I'm in the middle of trying to sort mine out too, so I'll tell you what I know, which is by no means comprehensive.
I tried to be as systematic as possible in the troubleshooting - first see if you can get a workshop tacho to work by wiring it hard to the "tach" outlet on the dist. It'll probably have an earth and a "pulse" wire, so pulse goes to the tach spade and earth goes to the block etc. If you get any movement on that, as i did, then it suggests the problem's further up, naturally. The next bit i'm not so sure about. If you were to wire up the good tach guage just after the filter, then i assume it should still work if the filter's good. This might be BS on my part - hopefully someone can enlighten us So if a known good gauge doesn't work downstream of the filter then, either
the filters died, or
my idea is wrong, and it's not supposed to work because the signal has been suppressed the very presence of the filter - or something:D I hope u get my meaning!.
I hooked up a portable oscilloscope to the wire after the filter and got no signal at all. So i reckon my filter's died.
If you do get a signal downstream of the filter, then i guess the next in line is the tacho. You could then whip out the board and put the known good tacho on the pins in the cluster... 12v, 0v and pulse. If there's nothing there, its a wiring problem. If not, then i guess its the board.
I really need someone to tell me if a working system would actually be able to move a workshop type tacho gauge if you put it down stream of the filter - to see if my trouble shooting technique is actually valid... i know very little about instruments and electronics, so i'm not sure.
One thing though, i found a link to a guy who builds replacment tach filters for about $20. I was going to get hold of one of his, then try my old board again. If nothing, then i know everything else is working, so its new board time. Look at http://my.execpc.com/~rodney1/corvette/