Hi, My tach, gas and three gauge in my 73' Grande are not working. If I turn the key, gas gauge will work until I start the car. Sending units for temp and oil pressure are new, above engine wiring and Alt. wiring for gauges is new. Alt. and regulator are new also. I'm not getting power to the gauges. Coil has two wires on the Battery side(tach and power) and one on Dist side going to the Dist. I'm going to test the Alt. to make sure that its working properly and clean the ignition switch. Have checked all grounds and wire connections. Tach and all gauges have been cleaned and tested. Any other ideas. Please HELP! Thanks, Brian
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Tach and gauge wiring problems
- Thread starter bbergy6
- Start date
Sluggo
Active Member
I would look at the circuit board on the back of the cluster. When I put mine back together after painting it, one of the tabs on the printed circuit was folded over where the connector plugs in. A little contact cement under the copper tab fixed it right up.
tarafied1
Well-Known Member
Is it a factory Tach? When did you notice them quit? Did they float any before quitting? Do the instrument lights still work? Any mods we should know about?
blue65coupe
Well-Known Member
Was the wiring already done or did you do it?
70_Fastback
Hell Bent for Speed
Does your gas gauge function if you turn the key backwards (is that the ACC position?) ?
I replaced the alternator and that fixed some other problems. Now my gas and temp gauges will go back and forth. Oil and alt. gauges don't move at all. When I turn the key to Acc gas gauge will move to full and then back to empty. I will check the grounds again and thinking of cleaning the ignition switch. Thanks for your time. Brian"70_Fastback" said:
I replace my idiot lights to gauges. Replaced the wiring and checked wiring by ohms meter to make sure the wiring was good. It is a factor tach. At 55-60 mph tach bounces 1000-1500 rpm. All gauges have been tested. Lights do work on all gauges. Thanks for your time. Brian"tarafied1" said:
I did all the wiring. Replacing idiot light for the gauges. Replaced wiring harness for the correct harness for gauges and tach. I replaced the alternator and that solved some of the other problems I was having. Please read the other post for more info. Thanks, Brian"blue65coupe" said:
These two statements are contradictory. The factory tach and wiring will only have one wire going to the coil (battery side). Are you running an aftermarket distributor system?
When changing from non-tach to tach wiring, did you change both the alternator harness, gauge harness and light harness (the three harnesses under the hood)? You have to do so to ensure things are wired correctly.
I have installed a pertronix ignitor under the distributor. Have replaced alternator harness, over the engine harness and under the dash harness. I only have two harnesses under the hood.(over engine and alternator). Where does the third harness plug into. Is the light harness and over engine harness the same. If the light harness is for the head lights, side markers, and tail lights I have not changed that harness. Thanks, Brian"Midlife" said:
You're right...71-73 are odd years in that there's only one feed from the firewall.
The underdash wiring is not available in reproduction, so I would start there in determining if the lines to the tach have the correct resistance and such. There are times that a tach can fail and the car can still run.
The gauge power lines come from the constant voltage regulator, which plugs into the circuit card on the back of the dash. The input power usually comes from the ignition switch.
What I'm trying to say is that whatever underdash harness you installed may need some work to get it up to snuff. I've found in my harness refurbishment business that many connectors and pins fail due to not being crimped tight enough (about 10-30%).
The underdash wiring is not available in reproduction, so I would start there in determining if the lines to the tach have the correct resistance and such. There are times that a tach can fail and the car can still run.
The gauge power lines come from the constant voltage regulator, which plugs into the circuit card on the back of the dash. The input power usually comes from the ignition switch.
What I'm trying to say is that whatever underdash harness you installed may need some work to get it up to snuff. I've found in my harness refurbishment business that many connectors and pins fail due to not being crimped tight enough (about 10-30%).