Tach not registering

[mtbadbob]

Tach filter?

A good connection might make a difference. A tach filter is the wire that usually runs from the distributor through a condenser looking thing that mounts to the firewall near the distributor, then continuing through the firewall to the tach. It usually has a rubber grommet that seals the hole that penetrates the firewall. I know they were used into the 80's. They were used to stop rpm noise through the radio.

 

[AuroraGirl]

A good connection might make a difference. A tach filter is the wire that usually runs from the distributor through a condenser looking thing that mounts to the firewall near the distributor, then continuing through the firewall to the tach. It usually has a rubber grommet that seals the hole that penetrates the firewall. I know they were used into the 80's. They were used to stop rpm noise through the radio.

thats a different one fro the radio

 

[mtbadbob]

thats a different one fro the radio

I know when the filter fails, the tach stops working. Had to replace them on a Monte I had.

 

[AuroraGirl]

I know when the filter fails, the tach stops working. Had to replace them on a Monte I had.

Radio supression condensors are attached to the coil

But interesting on the filter

 

[mtbadbob]

I traced the wire from the gauge to the distributor and it has definitely been altered.

The terminal has a aftermarket female terminal on it that is very loosely plugged into the tach port.

I’m going to replace the terminal and see if it fixes the issue.

Does that brown wire run right into the firewall? There's a good chance that the po removed the stock filter when he swapped the aftermarket tach. Now that you're re-installing the FT, a filter will more than likely make the tach work.

 

[jimmy78]

Does that brown wire run right into the firewall? There's a good chance that the po removed the stock filter when he swapped the aftermarket tach. Now that you're re-installing the FT, a filter will more than likely make the tach work.

The brown wire runs through the firewall right to the gauge. I have not spotted a filter that I can tell as of yet. There are 2 items that I can’t seem to identify.

One on the fire wall and one behind the dash with a pink wire going to it.

 

[jimmy78]

Radio supression condensors are attached to the coil

But interesting on the filter

I tested power to the tach 12v
I tested ground good continuity
I tested the tach signal wire good continuity

The gauge pegs to the bottom every time.
When I turn the blinker on you can see the needle twitch with the blinker.

Dirty ground?
Screwed gauge?

 

[AuroraGirl]

I tested power to the tach 12v
I tested ground good continuity
I tested the tach signal wire good continuity

The gauge pegs to the bottom every time.
When I turn the blinker on you can see the needle twitch with the blinker.

Dirty ground?
Screwed gauge?

could be grounds, hows your ground bar under the dash on look like

 

[jimmy78]

could be grounds, hows your ground bar under the dash on look like

 

[AuroraGirl]

I would be taking that park brake pedal off, the bus bar, cleaning it up. the connections for the original ground to the dash is not OE, so it could be improperly crimped too

 

[jimmy78]

I would be taking that park brake pedal off, the bus bar, cleaning it up. the connections for the original ground to the dash is not OE, so it could be improperly crimped too

The joys off taking on someone else’s projects lol. I’m just happy the engine and the body are in great shape.

 

[jimmy78]

The joys off taking on someone else’s projects lol. I’m just happy the engine and the body are in great shape.

My favourite is when I hit the horn the instrument lights flash lol. I have no fuse in that circuit‍

 

[AuroraGirl]

My favourite is when I hit the horn the instrument lights flash lol. I have no fuse in that circuit‍

OOF

 

[mtbadbob]

I tested power to the tach 12v
I tested ground good continuity
I tested the tach signal wire good continuity

The gauge pegs to the bottom every time.
When I turn the blinker on you can see the needle twitch with the blinker.

Dirty ground?
Screwed gauge?

I'd maybe send your tach to someone like Redline Gauge and have it tested, possibly repaired & recalibrated.

 

[jimmy78]

I would be taking that park brake pedal off, the bus bar, cleaning it up. the connections for the original ground to the dash is not OE, so it could be improperly crimped too

Cleaned up the terminal block, crimped new ends on both the ground and the signal wires. Added a ground from the head to the firewall. All gauges are alive now with the exception of the tach. I think I’ve kicked the dead horse enough and I may have to purchase a new tach. Fingers crossed it solves the issue at $300 Canadian.