70 Bouncing ammeter

[Chris H.]

My '70 454, has a bouncing ammeter that smoothes out at about 1500 rpm. I presume theres a loose connection somewhere in the circuit. Any ideas on where to check would be greatly appreciated.

Thanks, Chris

[Jack H.]

Re: 70 Bouncing ammeter

First, check the connections to the dash gauge itself. This is a 'yuk' job because the instrument center cluster is PITA to loosen/remove. Follow instructions for removal in the Chassis Service Manual and be VERY careful when you slide the center cluster out from under the upper dash--it's designed to have intentional weak spots for crash/break-away (just below the A/C vent area that may be plugged with Corvette insignia on non-A/C cars).

If you're good with working in tight places, you may be able to see/reach the backside of the cluster from the passenger side with the lower RH dash panel removed. Also check for lead wires that are skinned and making contact with other wires and/or ground points (strut rods, Etc.) behind the center cluster.

If the ammeter is OK, it may be that the altenator is REALLY turning on/off in erratic bursts. This requires checkout under the hood. You might actually want to start here first since it's easy to reach....

On the side of the alternator is a 2-wire plug-in. One of the wires supplies B+ to power the alternator's internal voltage regulator and the other is a battery sense wire. Both can be frayed and making intermittent contact, visually inspect them for good/solid contact to the crimp-on connectors inside the plug's hood. If either is flakey, the alternator's v-reg can be intermittently powering up/down and/or the v-reg can be intermittently seeing the system battery (sometimes it's there other times it isn't).

Last, these signals arise from the engine compartment B+ bus bar. That's the metal rail on the side of the horn relay. This is ALWAYS HOT regardless of igntion switch, be careful!!!! There are a number of crimp connector wires bolted here, several on top of each other.

You're looking for a flakey/loose connection as well as corroded contacts. You want all surface metal to be clean and the center terminal screws to the bus bar to be tight.

If this doesn't 'get it', you might have an intermittent connection in the main wiring harness connectors (multi-pin) that are on the LH side of the engine firewall and bus through to the cockpit/fuse panel.

[Chris H.]

Thanks Jack *NM*