Tach trouble.(pics)

[BamaDave]

I finally got the factory tach put in my truck and at idle it is reading 1750 rpm. Surely this can't be right. I did put the filter in the wire from the tach hook up on the HEI to the "tach" hook up on the gauge. I guess the thing is going to have to be rebuilt or refurbished. Can anyone recomend a place to get this done? I hooked the 12v terminal on the tach to a ignition source of +12v. I think this is right. When I rev the motor it goes way outside the tach readings. I would appreciate any help here.

[3r!c84]

what is it at when key on. motor is not running. it should be at 0

[BamaDave]

When I shut engine down the tach usually stays close to where it was idleing, but when I turn the key to start the engine it snaps back to 0.

[3r!c84]

and when you start it up it jumps up to like 1750 you say

[BamaDave]

I just added a pic where it is showing where it is when I shut down the engine.

[BamaDave]

yes about 1750 rpm, and moves as I rev it.

[BamaDave]

anyone?

[76stepsidechevy]

you sure you have a v8 tach there? that sounds about what a 6cyl tach might read when used with a v8.

[BamaDave]

came out of a 80-82 blazer, did they have v-6's in them?

[RandyP]

Just like most trucks from those years, the "standard" engine was a 6 cylinder. It is possible, but I would think if the Blazer had a nice tach cluster setup it would be a nicer truck with a 305 or 350 V8 option. You never know though.

[BamaDave]

Surely someone on here knows how to or who can fix this thing.
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[1BadSS]

Sometimes a simple search is your best solution.

http://67-72chevytrucks.com/vboard/s...d.php?t=433323

Thread mentions a company who is in tune with fixing these tachometers. Does yours say 8cyl or 6cyl on the back?

[BamaDave]

I didn't notice, where would it be?

[rayfinseats]

you sure you have a v8 tach there? that sounds about what a 6cyl tach might read when used with a v8. X2

I'd look at EBAY for just the tach part. I'd trade you a factory clock for the small fuel gauge...1983 chevy k10

http://cgi.ebay.com/ebaymotors/73-91...item45f7bf3c1e

[RandyP]

Coil, ground and 12v, so easy a caveman could do it. Bad thing is though, when a tachometer goes bad, they read higher than normal and the higher the RPM the more off it gets.
Tach's are very easy to test before you go through all the bother to install it permanently.

[dswancutt]

Have never used these guys, but they advertise that they repair 73-80 GM Truck tachs.

http://www.tachman.com/oldsun.htm

[joe231]

Tachman wants @$300 to fix one of these.
One of my factory tachs were doing the same thing, read very high at idle and would peg when I reved it up.
I do know how to repair it but it involves some delicate soldering.
Let me do some checking and I will get back to you.
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[83burban]

I started the other thread you guys referenced earlier and have made alot of progress with my research.

Tachman wasn't as nice I had heard when I called him, and I got the overall feeling that he wasn't the guy for my job. I am going with a company called Redline Gauges.

For about 300 they are going to put a VDO tach motor into my existing cluster, reface the gauge with a factory correct font according to my specs for redline and range. They are also going to calibrate the whole thing so that it is accurate.

[BamaDave]

joe231, let me know what you find out. I am an electrician by trade and can do the soldering very easily.

83burban, I think that company is in or around Jackson, TN right?