Ammeter WTFO!!

Reply Subscribe

Thread Tools

Search this Thread

Dec 10, 2004 | 06:05 PM

Cali,68,L-79

Thread Starter

Le Mans Master

Joined: Jan 2001

Posts: 6,938

Likes: 1

From: San Diego CA

Ammeter WTFO!!

Last night I just finished installing the new Petronix II flame thrower coil and drove the car in today. Car seems to start easier etc, but I guess I never looked at the ammeter guage becuase when I did it's butted up against the positive stop way past the max reading and the top ofthe pointer is broken off and laying at the bottom of the guage glass. It's like the little metal pointer pounded itself into submission against the pointer stop until it fractured in 2. Now the guage is stuck in that position whether the cars on or off.

WTFO!!!!!!!!!!????????????

What would cause this? When I got home and read the voltage regulator it was putting out 12V with 12Vs coming out of the altenator while at idle. I want to figure this out before I buy another ammeter and tear out the dash just to have it happen all over again. Car running fine otherwise.

Dec 10, 2004 | 06:09 PM

Twin_Turbo

Race Director

Joined: Dec 1999

Posts: 16,945

Likes: 9

Sounds like you shortcircuited and killed the ammeter doing so. You did remove the battery ground cable before hooking the petronix up right? Did you test current draw with a DMM after this happened? I would certainly unhook the battery if you're unsure what's going on, wouldn't want to burn the car to the ground

Dec 10, 2004 | 06:24 PM

80Xflags

Pro

Joined: Feb 2003

Posts: 508

Likes: 1

From: Maplewood NJ

Quote:

Originally Posted by Cali,68,L-79

When I got home and read the voltage regulator it was putting out 12V with 12Vs coming out of the altenator while at idle.

Don't confuse amps and voltage

To read voltage the meter is in parallel with the load. For amperes, the meter is in series with the load, and if you draw too much current through your meter you'll pop it's internal fuse. That sounds like what happened to your amp meter in the car, except there's no internal fuse to protect it, so it self destructed.

Goodluck

Dec 10, 2004 | 06:40 PM

Cali,68,L-79

Thread Starter

Le Mans Master

Joined: Jan 2001

Posts: 6,938

Likes: 1

From: San Diego CA

Sadly no I did not disconnect the battery. More than likely the cause however neither power source had power until the key is inserted and turned to the right and the key wasn't anywhere around so I can't see how it magically powered itself.

Prior to coil swap
one lead from fusebox (12V) to inlet ceramic ballast resistor (main coil power supply)
One lead from starter circuit to outlet of ceramic ballast resistor (starting current for coil, no power after starter disengaged)
Petronix does not use the ceramic ballast resistor just points so I tied both wires together and goes to coil positive terminal.

Pertronix II module red comes off coil positive and P II module neg comes off coil neg done verbatum with Pertronix wiring diagram and instructions

Again the job was done correctly and the car drives great!! It may be due to not disconnecting the battery but again
"neither power source had power until the key is inserted and turned to the right and the key wasn't anywhere around so I can't see how it magically powered itself and short circuited."

Last edited by Cali,68,L-79; Dec 10, 2004 at 06:44 PM.

Dec 10, 2004 | 08:48 PM

Cali,68,L-79

Thread Starter

Le Mans Master

Joined: Jan 2001

Posts: 6,938

Likes: 1

From: San Diego CA

ttt Just went for another short drive, car running perfectly just a dead ammeter. Any other advise?

Dec 10, 2004 | 10:10 PM

goinbroke

Burning Brakes

Joined: Jun 2002

Posts: 837

Likes: 3

From: Texas

I don't have an answer to your question, but this will bump you back up........and give me a chance to tell ya that is one fine looking vette.

Dec 11, 2004 | 01:58 AM

MN-Brent

Le Mans Master

Joined: Apr 2001

Posts: 5,000

Likes: 1

From: Minneapolis, Mn USA

Swap in a new ammeter (with battery disconnected) and see if all returns to normal.

You may have accidentally shorted something during installation or some type of inrush type current is going to the Pertonics ignition that has taken your old ammeter beyond the point of no return.

Originality dictates an ammeter. I feel (along with the rest of the automotive world) it is a bad design and should be replaced with a voltmeter.

The wire leads from the ammeter could be connected together and insulated up under your dash and a voltmeter installed from a good 12V source and to chassis and this would give you your simple alternator on/off, 12V or 14v, status.

Brent....

Dec 11, 2004 | 12:47 PM

Cali,68,L-79

Thread Starter

Le Mans Master

Joined: Jan 2001

Posts: 6,938

Likes: 1

From: San Diego CA

Brent i guess what I'm going to do is order the ammeter than with the dash out start the car and get measurement readings off my meter and if their within limits I guess it should be safe to reinstall the new ammeter. I think I can pull the center guage bezel out without removing the left or right lower dash pads. I t looks to be held in by 4 screws.