67 Ammeter Question

[Al P.]

Re: 67 Ammeter Question

I don't believe the gauge has modified itself. I believe you have a high resistance in the sensing circuit causing the voltage drops in the sense wire to be greater than normal. That is why your readings are high in both directions, the voltage drop across the sense wire is greater than normal. When no current flows either ito or out of the battery, the sense wire does not create any voltage drop to move the needle. I'd start with the connections at the firewall and look for corrosion.

Yeah, The bulkhead connectors on the firewall - I can't get them apart to check them - That's a whole other story! Man this is frustrating!

[Al P.]

Re: 67 Ammeter Question

Yeah, The bulkhead connectors on the firewall - I can't get them apart to check them - That's a whole other story! Man this is frustrating!

Ok - with the battery disconnected - I was checking for continuity on my horn relay from that black wire that has the red fuse link on it that supplies battery power to the innards of the car. It looks good. The I put my ohmmeter between the battery bus bar on the horn relay and the ground on the horn relay and a get a reading of.456 on the 20 K ohm scale.

So I'm think that this should be zero, shouldn't it? or is this reading coming from one of the circuits that they are connected to.

Some my question is - With the battery fully disconnected - what OHM reading do you get when you checking between the horn relay 12v bus bar and ground of the car?

If someone would be good enough to check this Id greatly appreciate it. Thanks So Much! Al

[Al P.]

Re: 67 Ammeter Question

With the battery disconnected, the red ohmeter lead on the 12volt connections on the horn relay and measuring to chassis ground and engine ground read .5 ohms.continuity which is from what I am told is normal.

Measuring to the negative battery lead open.

Measuring to positive battery lead read .5 ohm

I'm beginning to think that my problem could be wiring in the starter area or perhaps the started or the solenoid as well......I measured the battery cable to ground down there and I get .5 ohms as well - which is correct. When I check for continuity on the 12v single brown lead to the starter I get solid ground (short) But the starter works fine - this is the lead that get 12volts when the key is moved to "start".

[Al P.]

Re: 67 Ammeter Question

A good friend of mine that works on these cars every day says the problem is the Vette needs a Ground Cable installed between the engine block and the frame.

He said this is a very common issue as the 67's require this - So Ill install that this weekend and see what happens.

[Wayne W.]

Re: 67 Ammeter Question

A good friend of mine that works on these cars every day says the problem is the Vette needs a Ground Cable installed between the engine block and the frame.

He said this is a very common issue as the 67's require this - So Ill install that this weekend and see what happens.

Should already have one.

[Al P.]

Re: 67 Ammeter Question

Should already have one.

and where is it?

[William C.]

Re: 67 Ammeter Question

Actually there are several built into the wiring harness. One is at the starter and grounds the heater blower and wiper. Another is to the radiator support support via the ring terminal that attached the horn relay to the core support. That one also grounds the voltage regulator. Another ground is via the alternator. Have you checked all of these to see you have secure attachment and no broken wires? If you have a service manual, the electrical diagram is Sheet 12-24 and 24 in the electrical section. Grounding to the frame generally will not due much as the battery negative is not directly attached to the frame. The frame grounding is accomplished via the ground on the rad core support.

[Wayne W.]

Re: 67 Ammeter Question

and where is it?

Motor mount bolt to frame.

[Al P.]

Re: 67 Ammeter Question

There has to be a solid Ground wire from the block to the frame, in addition to all others.

"All 67's originally had a braided copper ground strap from a LH engine mount-to-block attaching bolt to a hole in the front side of the LH engine mount bracket on the frame"

On my 67 BB - no braided copper anything under there......I have changed my motor mounts too many times during the past 45 years to remember ever seeing that! LOL I now have poly engine mounts. Have them on for years now.

So I plan to run a 2 guage battery size cable between one of the engine mount bolts to the frame on right side of motor. That is overkill and should take care of the motor to frame ground requirement.

I suspect that the Alternator is seeing a high resistance to ground, resulting in high ammeter readings in both directions, as the frame needs to be grounded to the block to make the alternator ground requirement happy. This is very common in these cars and over the 45 years thus far, things change..... Ill keep you posted.

[Al P.]

Re: 67 Ammeter Question

Another question - I have a moroso battery on off switch at the rear of my 67 and it connects the battery ground - and back to the engine ground. So it completely discconects the battery ground - when the car is not in use and switch is in OFF position. Think of it as a long 2 guage negative battery cable with a heavy duty single pole (2 Lugs)switch in series of the long cable going back to the starter.

Front of car
- post of battery ___________________________XSwitchX_____ _rear
- to starter bolt ________________________________________ _I

It has been fine for years now.

But Im reading that some dont run a return cable and connect the switch end back to the frame and the negative cable from the starter motor ground to the frame. The frame becomes the return wire.

Front of car
- post of battery _________________________XSwitchX____XFr ame Rear

- to starter bolt ___XFrame
This way the frame is the return path to the engine starter - negative

Is ther a preference to doing one over the other?

[Al P.]

Re: 67 Ammeter Question

Update - Problem Resolved It was the wiring on the starter that was at fault.
Pulled the starter out to check the harness wiring at the solenoid.
There was a loose wiring connection on the red wire that's on a fusible link to the battery cable on the starter solenoid. This is the red wire tha routes to the horn relay. The Battery gauge reads one side from this point.
I repaired that connection and now my Battery Gauge is working perfectly again! Reading Straight up when driving (Battery is fully charged). Works perfectly again now! Thanks for all of your responses.