Gauges work, then don’t, then do

[Mopar Luvr]

Hey everybody. I solved a no-start issue on our 74 Road Runner,
(including a new ignition switch, neutral safety switch, starter relay…all parts I had around), got her running. (Also, a new ignition key lock)

Here’s my issue now:

1)key on, gauges go live. Great
2)start her up, fuel level goes up, amp meter is live. Great

Now the odd part:

3)After she’s running, the amp meter stays in the upper charging area, but the fuel and oil pressure, and temp gauge if she’s warming up, all return to “off” or no reading.

Now the weirdest part:

4)*** and here’s the big one…..put her in gear(727) and the gauges come back to life. Again, amp meter is in the upper charging area.

Any ideas?

Thanks in advance.

 

[RemCharger]

The amp gauge is separate and independent of the rest of the gauges. What it's doing matters not.

 

[Doorkicker]

put in drive, then park, then reverse, and then in neutral. If the guages do their wried on/off in both park and nutral... you may have an issue with the NSS wireing. This could be related to how you terminated to the new starter relay.

as for amp guage... if it is connected to anything other than the wires it is intended, you may be pulling power off the terminal, which is usually undersireable, and that could be causing the condition indicated on the guage. I doubt that would cause oil, temp etc. guage to go off and on.

My gut points to a NSS wireing issue, combined with some other power issue. Keep oin mind every cirtuit you've mentioned goes through the firewall harness blocks.

 

[Mopar Luvr]

Thanks for your reply. The only wiring changed was the ignition switch, basically a plug and play connection. NSS was simply swapping the switch. Key lock, purely mechanical.
** Let me throw this in there:
I don’t remember the key buzzer ever working, but after the key lock and ignition switch were changed, the buzzer was functioning afterward.
It was brief, then the buzzer was no longer buzzing soon after the installation.
Could there be a common link between the buzzer and the gauges?

 

[kiwigtx]

The common link will be a loose ground wire.

Have you had the steering column out of the car? Check grounds first.

 

[Fran Blacker]

As Kiwi check instrument panel ground, amp gauge has nothing to do with the others.

 

[72RoadrunnerGTX]

Thanks for your reply. The only wiring changed was the ignition switch, basically a plug and play connection. NSS was simply swapping the switch. Key lock, purely mechanical.
** Let me throw this in there:
I don’t remember the key buzzer ever working, but after the key lock and ignition switch were changed, the buzzer was functioning afterward.
It was brief, then the buzzer was no longer buzzing soon after the installation.
Could there be a common link between the buzzer and the gauges?

View attachment 1915623

May not be related to your issues as described but the small black wire in the replacement switch needs to be removed from the connector for that application.

Details;


For that cluster, the wired ground connection plugs into a spade on the mounting tab for the voltage limiter and runs to the harness to dash frame ring terminal, lower left on the frame near the parking brake.

 

[Mopar Luvr]

You know, I noticed that “additional” wire in the new ignition switch connector, but I guess I dismissed it when I realized that there is a wire matching up to it. I will get a look at it tomorrow and pop it out and see if any changes occur. Thanks for pointing it out.

 

[72RoadrunnerGTX]

 

[Mopar Luvr]

Thanks for that page. I should have checked my repop service manuals.
It sure would be nice if the sellers of the ignition switches would include that information. Not even an installation sheet.

 

[Mopar Luvr]

View attachment 1915852

Well, no change from removing that black wire.

 

[72RoadrunnerGTX]

Well, no change from removing that black wire.

As mentioned, the ignition switch wire issue was likely not related to the intermittent gauge issue. Have you verified the cluster and voltage limiter is grounded. Next check the keyed power supply to the voltage limiter.

 

[Mopar Luvr]

I don’t know if this has any impact, but before the no-start issue arose, I’d had an issue with the gauges dying off while driving or even idling.
Working that “white” wire in the “bluish green” connector would bring the gauges back to life. While I was dealing with everything the other day, I made it a much more secure connection by making a bypass around the connector(red wire on the right).

 

[72RoadrunnerGTX]

That white wire in the turn signal switch connector comes from the brake switch, should have nothing to do with the gauges or the power supply to the voltage limiter. You need to get at the voltage limiter to check it and its connections. That cluster has several ground paths when installed and likely is not the cause of the gauges not working. Easiest way to get at it is to drop the radio out. The voltage limiter is just above it and accessed easily with the radio out of the way. Again, it is the only thing the three sweep gauges have in common, no relation to the ammeter. The limiter could be bad, not securely mounted to the cluster, or the keyed power to it could be intermittent for some other reason.

 

[Mopar Luvr]

Well, I had an epiphany late this morning…….what’s the battery voltage both off and running?
I had time to run home during my lunch and throw my meter on it.
A nice 12.6 off
Running………about 17.6!
I ordered a new voltage regulator, will have it tomorrow.