Tach repair

[PT'S 70 CST]

Has anyone sent off one of these tachs for repair. I have one that I cannot get to work and I think it is a bad resistor in the board but cannot find anyone local that will fool with it. I know there are several places that work on and restore these but the price is outrageous. Just checking to see if anyone knows of anybody that fools with these that will not charge an arm and a leg.


Thanks PT

[Daddy'O]

Subscribing......

[Ironhorse]

Also subscribing, my tach quit registering more than 2,100 - 2,200 rpm. Otherwise works fine. Interested to know who can diagnose and repair at resonable $$. Good luck, PT

[davepl]

Just FWIW, I have a repro tach in mine and they're relatively cheap and look very good (one of the few reproduction parts I'd say that about). Always an alternative... and you don't need to toss your original, just hang onto it.

[PT'S 70 CST]

Ironhorse take your tach out and move the needle to make sure it is not hanging up on the face plate. I have seen this happen alot when the plate gets bent out a little the needle will make contact with the plate and not move any further. You can also take the face plate off and where the needle moves inside that metal block is magnified and it will pick up debris and cause the needle to stick. You can buy a can of compressed air like you would use to clean you pc key board and blow that area out. Just a few things you can try to see if it will fix your problem.


PT

[chevykevy]

Anyone have a tach they believe is registering too high of an RPM reading? I think mine is. 3:73 and a 700r4 with 28 inch tall 15 inch whells and I am reading about 4,000 rpm at 70 mph?

[blasher]

Originally Posted by chevykevy

Anyone have a tach they believe is registering too high of an RPM reading? I think mine is. 3:73 and a 700r4 with 28 inch tall 15 inch whells and I am reading about 4,000 rpm at 70 mph?

Mine reads too high. Turns out I've got a 6 cylinder tach and I'm running a V8. You may have the same problem based on your info.

[Ironhorse]

PT, thanks for the tip. Will look at that possible problem. Can't really tell right now as the engine, transmission, and transfer are out for a manual to auto swap. Sounds like something to check into for sure, thanks again for that one.

[bonnieclyde100]

yea chevykevy 4000 rpm for 700r4 and 3.73 is to high mine runs around 2200-2300 at that speed with same setup

[chevykevy]

PT, sorry for robbing your thread. Just thought we have similiar subject matter so figured I would join in.

Just put the tach dash in last week out of a 68. The tach says V8 on the rear and appears to be pretty accurate at idle. I may hook up an aftermarket tach I have and check it out.

[GMCJOE]

I hear these guys are the best out there for repairing and restoring your gauge clusters. Seen that a few members that restore them send them off to this company. One of the members that sells the restored ones, I think send them off to them. Can't be for sure on that, but it seems to be what I read.

http://www.redlineg.com/redlineg/Welcome.html

[Dave]

PT,
What's wrong with the tach? What are symptoms? You mentioned the possibilty of a bad componet. LMK, curious.
Dave.

[PT'S 70 CST]

The tach will not do any thing. Checked the ground the ground wire and looked for any burnt spot. I did talk to a guy that does TV and PC repair and he said that when the resistors go bad they usually swell up but do not see any that look abnormal.


PT

[Dave]

You need to determine if it's a meter or board problem. Do you own a multi meter that can read ohms? If so, there's a black and white wire on the board going to the meter assembly. Take your multi meter and select the lowest setting in ohmic value it has and read between the 2 wires. If the tach needle deflects upward, the meter is good. Don't worry if it deflects downward, just switch your leads and watch the tach deflect upward. The point is checking the tach meter field.
Checking each component on the board is more involved. However, a simple visual inspection of the board can reveal things, i.e., leaking caps, open diodes, etc. Using your meter again, check for cold solder joints on every connection, very common problem. These are a few basic examples that you could start with.
I could write an essay on this stuff and not cover it all. I'll leave that to someone else. Hope this helps you.
Dave.

[Already Gone]

Originally Posted by chevykevy

Anyone have a tach they believe is registering too high of an RPM reading? I think mine is. 3:73 and a 700r4 with 28 inch tall 15 inch whells and I am reading about 4,000 rpm at 70 mph?

I calculate you should be around 2200RPM at 70mph with that combo.

[john]

I had a 70 elcamino tach repaired by Bobs speedometer in MI. They did a good job at a reasonable price.

http://www.bobsspeedometer.com/1/120/index.asp

[chevykevy]

Already Gone,

Thats what I'm thinking too. I hooked up an aftermarket tach and as soon as the weather breaks I'll check it. I wonder if I'm getting interference from another wire or the tach needs recalibration.