fastbackford351

Are you sure the ammeter is bad? Are you 100% confident you have it hooked up properly? Because, again, as per Freddy, those old gauges rarely actually go bad and if they aren't working then it's usually because they are hooked up wrong. Not saying that it can't be bad, just that I'd be surprised if it actually was. It doesn't hook up like a voltmeter, it has to be in line with the charging system.

DALLAS916

The ammeter was not disconnected. It stopped moving in either direction before the entire Rally Pac quit. I think I touched a hot lead to a post on the fender-mounted solenoid unit, and that might have fried the meter. It definitely does not move when starting or running the engine. Just sits dead center.

fastbackford351

Before I ditched it, I'd run some temporary wiring just to verify it is really dead and not jinky wiring.

DALLAS916

Good idea. Most of the underdash wiring is original, though the main harness up front was replaced. That said, resistance reading at the two posts of the meter shows "0". That says the wiring is not involved in the status of the meter.

fastbackford351

Just for funsies I checked a couple ammeters I have laying around and they all showed 0 resistance across the post. A good quick way to bench test is to hook some test leads to your ammeter then take a 9v battery and tap the posts to see if the needle moves at all. It will barely move, but if it moves at all, dimes to doughnuts it's good.

DALLAS916

I tried your test and by golly, it moved the needle. It moved left toward discharge I think. Does that matter?

If the meter is actually functioning, odes that mean I can put the dash/instrument cluster back in? Or, do I possibly have a wiring issue between the cluster and the firewall??

fastbackford351

The way Ford wired the ammeter in is a bit odd too as I recall. I don't remember the particulars but I know it struck me as being odd when I was checking mine out. The best thing I can tell you is to get the factory wiring schematic, a meter with a continuity buzzer and a test light and start verifying the wiring before you reinstall the cluster.

Hell, it's a 50+ year old Ford so it can't be that complicated.

DALLAS916

We thought we had the tach issue licked, but after "testing" the ammeter by touching a 9V battery to the leads (it moved the needle a little) and verifying the wiring to each source of current had continuity, we put it all back together and started the car. First, the tach moved up to about 3K, then wouldn't go any further (farther?). Then, when we shut the engine down the tach needle settled at about 300 rpms on the guage, and doesn't want to go back to "0". Back to square one with the tach. Is it possible the mechanicals inside are just corroded a bit and will not move properly? It did work fine for SURE before the whole battery-clock-battery dying issue. I THOUGHT it worked fine when we put this back together and ran the engine a week or so ago. "THOUGHT" it did. I honestly cannot remember if I revved the engine past 3000 rpms, but why would I NOT have done that to test it???

OK: NEW INFORMATION! After going half blind looking at these original wiring diagrams and schematics, I see that the tach has ITS OWN "resistance wire" in the circuit. The PINK wire coming off the connector (black wire from the tach into this connector behind the instrument cluster), is the same resistance wire normally coming from the ignition switch and working its way to the coil in cars WITHOUT the Rally Pac. This pink resistance wire circuit is the substitute for the ignition-to-harness wire. It get to the main connector at the firewall and then turns red-green....which is why we could not find the pink wire at the coil or the solenoid. The resistance is supposed to be from 1.2 to 1.8 ohms for this CRITICAL wire. According to one source I found, "...THE TACH WILL NOT FUNCTION PROPERLY IF THE RESISTANCE WIRE IS DAMAGED....". This explains a lot.

Next, we will attempt to take a resistance reading from the PINK tach connection wire plug-in at the loom behind the cluster AND the red-green connection at the coil (opposite the connection to the distributor). Negative, I think. If it is not 1.2-1.8 ohms, the resistance wire is bad. HEY....could we just test from the connector to the main connection block where the wire changes color? From the other (non-Rally Pac) diagrams it looks like the only part that is "resistance" is the short, pink sheathed wire. Maybe?

https://www.cjponyparts.com/skin/fro...s/Tech_RP2.gif


And, the ammeter is definitely NOT working. !

fastbackford351

Damn. I forgot about the resistance wire. Damnit. Sorry about that, it's been a few years.

Since my car didn't originally come with a tachometer, I installed a ballast resistor so I didn't have to dick with the resistor wire. I mounted it on the fender beside the master cylinder.

As far as the ammeter goes, well, I guess you really might have screwed the pooch on that one.

DALLAS916

Hope this info will help some of you "guys" (not meant to be gender biased).

I finally gave up and took my GT to a highly reputable Mustang shop. They had the Rally Pac out in a few minutes. Tested the clock and tach. both moved with voltage applied, but still seemed to "hang up". The ammeter was pulled out with the entire instrument cluster in a few more minutes. With current applied, the ammeter swung BOTH ways....so it really does "work".

I sent the entire Rally Pac to Bob McMullen (RCC Innovations in Texas) since he had repaired/rebuilt my clock last year. He has already sent it on its way back after installing a new clock harness I bought at the Mustang shop, reset/adjusted the hands, and affirmed that is actually was working EXCEPT FOR THE MALADJUSTED HANDS. Same for the TACH. Bob says those old, original plastic hands can WARP over time and touch the face, surface, or other hands. He re-adjusted them all and says they are all working fine. Now, Bob did accommodate me with my car-in-shop situation by doing the work quickly. I would never suggest he could do that all the time, but he is really a PRO and a great customer-oriented guy.

I'll give more update when the RP gets her and gets re-installed. Bob only charged me for the tach adjustment.

Here's hopin'