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34 Posts
Discussion Starter #1
Hello Again,
1. replaced 72 sweep with a used 72 ss guage.
2. found out 72 dash harness was from a 70/71
3. re-pinned bulkhead for interchange of the harnesses.
4. new 72 hei engine harness.
5. got engine running (anybody remember the neutral switch problem,
, anyway.
6. turned motor off, connected brown tach wire from engine harness, cranks but no fire. if i remember right, the 70/71 harness has a separate
wire for the tach. is this true?
7. clock doesn't work either. have to check ground and single orange wire. i've read about the failing clocks over time.
8. gas gauge - stays at 1/4 full, even with full tank. have to try diagnosing the gauge using the
"chevelle engineer-fuel guage problem diagnosis"
9. took the car around the block, no speedometer
I'm sure i hooked that cable up.
10. no tach - see #6
11. new amp guage - stays at "0"
12. some dash lights works. the gas/temp lights,
have to check grounds, sockets and bulbs.
13. temp gauge falls below 100 - stays there.
14. turn signal dash indicators don't work but outer lights flash.
15. looks like a new dash circuit board.
16. light switch works all the lights except the
individuals in the dash.

Either I did a terrible job plugging the connectors together or i bought a bunch of guages
that don't work..... :mad:

7,762 Posts
Speedometer is a mechanical device. It uses no power to operate.
Might try and troubleshoot one thing at a time. Some of the other answers may show up along the way.
On your fuel gage:
Does it have 12 volts, on the pink wire, with the key on?
Does the car have a ground wire from battery (-) to the right inside fender? That's the body ground for the dash.
Tried adding a jumper from fuel gage black wire to a good ground on the dash? Change anything?
Tried adding a ground wire from the fuel gage tan wire to ground? With the key on the gage should go to empty.
Gage have the ceramic resistor on the backside?
See if that leads to any answers.

Premium Member
2,223 Posts
Just in case you missed them, the dash harness has two black wires with ring terminals. One connects to the parking brake the other to the metal back of the cluster.

Yes the 70-71 use a tach wire that is separate from the dash harness. 72 has the tach wire in the dash/engine harnesses. Sounds like the tach wire you connected to the distributor is somehow grounded.

34 Posts
Discussion Starter #4
THanks John and Elree
You guys are a great help....
I got the speedo working, connecting the cable
really does help. duh..
Doing nothing else, now the gas guage reads full
or pegged past the full mark. and the oil light
and the brake light is on constantly, even when the key is off. I guess I'll be dropping the dash the rest of the way to review the cluster.
Like John says -one step a time.
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