Replacing the ammeter

[dkoppyus]

I just bought this 1966 tbird and it was missing the ammeter. I got a replacement but the wires behind the dash clip has 3 wires 2 black and one white. On the ammeter there is 2 wire lugs? According to the wiring diagram it only shows as a connector. Can anyone tell me what wire/s go where on the ammeter?

[sseebart]

Sounds like you might have picked up a 64 style amp gauge.

[makrie]

Since I've never seen the ammeter connection I can only surmise some facts from the schematic which may or may not apply in your case. One wire should be #8 gauge and eventually terminates at the starter solenoid relay. Another should be #10 gauge which parallels all the loads including the ignition and lights. I cannot find a reference for a third wire so I'm assuming it might handle illumination of the gauge itself. Note: Like most factory installed ammeters Fords use a shunt circuit to reduce the possibility of a fire in the gauge cluster.

Sorry there are no colors listed on the schematic I have currently. You'll have to do some circuit tracing to confirm all of the above. Success here depends on your knowledge of electrical principals, testing equipment (VOM), and your willingness to crawl all around the car to confirm everything.

Note: Never guess based on these descriptions, you can fry your electrical components or worse set the car on fire!

[Terry64HT]

Makrie, only the 65 and 66's used a shunt for the ammeter. The full output of the alternator was dumped through the gauge in the 64. Lots of fires over the years, including mine.
I agree with Steve, sounds like a 64 ammeter. It won't work in a 65 or 66.
Terry
64HT

[makrie]

@Terry64HT Thanks for the clarification... My explanation in regards to identifying the 3 wires without a connector and was not intended to distinguish the ammeter from model years. The schematic I referenced was for the 65 which as you accurately pointed out shares some components with the 66. I haven't looked at the connector side of my 65 and hope I won't have to for some time. KNOCK ON WOOD!

That said I believe all ammeters use two primary wires, the ones requiring a shunt must be matched to the resistance of the circuit. From your clarification earlier ammeters are not compatible with shunted circuits common after 65.

Perhaps you or others can describe to the rest of us who haven't had a chance to dig in the inner workings how the later ammeters appear? Pics would be awesome if you have any? Thanks in advance!

[Terry64HT]

Makrie, I may have replied a little to quickly. I have looked at the wiring diagrams for both 64 and 65, and both show two wires to the ammeter. I haven't had a chance to look further to see what the difference is in the rest of the circuit, but will do so.
When I purchased my 64 in about 2000, the ammeter showed signs of overheating and smoke damage. I replaced it and did quite a bit of wire repair caused by obvious overheating. The forums of the time had quite a bit of information on the problems caused by all the output of the alternator being fed through the ammeter and Ford changing the design for 65.
I also recall an article about modifying a 64 to solve the problem, but I haven't yet found it (still looking).
Perhaps someone else can give some information on this.
I'll get back to you
Terry
64HT

[dkoppyus]

Thanks that helps a lot, I removed the ammeter from the dash clip and it appears the coil is burnt. I started tracing the wires behind the dash and, realized some people should not be working with electronics. I've got a mess to sort out

[makrie]

@dkoppyus I want to make sure I'm clear on your inquiry. Are you saying you have a 3 wire connector or 3 cut wires? My previous responses were based on the latter scenario.

@Terry64HT Based on anecdotal information and review of the schematic I think FORD used resistance in the wires to act as a shunt vs. late model ammeters with built in shunts. The resistance is not as critical as an ammeter that has to convert to a specific read out eg. 10, 20, 30 amps etc. In my 65 its just a charge or discharge indication not requiring that level of precision.

[dkoppyus]

It appears one of the black wires is an added wire being stripped then to the dash frame, the white wire seems to be a jumper going to one of the connectors. Just pushed in the connector ends. The wires that were exposed from the front of dash were cut but after looking deeper they were wires put there by someone not knowing what they were doing.

[Terry64HT]

I compared the wiring diagrams for 64 and 65 and, hopefully, I can explain.
In the 64, the wire comes from the battery terminal on the solenoid, through the ammeter, then on to the ignition and light switches. All the power from the alternator goes through the ammeter.
In the 65 (and I assume 66), the wire goes from the battery terminal on the solenoid to the fuse panel. Before the panel, there is a splice for a wire to the ammeter. The other side of the ammeter is spliced in to the wire between the ignition and light switches. The ammeter is only "sampling" the power.
Over the years, there have been a number of posts telling how to make the 64 wiring more like a 65, and, if needed, I'm sure I can dig one or two up.
Hope this helps
Terry
64HT

[Terry64HT]

dkoppyus, I forgot to include that the two wires connected to the ammeter are usually black and fairly heavy, 8 or 10 gauge. There is a black plastic block that covers the connections and it is often broken or partially melted.
Tery 64HT

[dkoppyus]

I will have to look at the wires again, with your information. I am not sure if it was a '64 ammeter or not, is there a way to tell? This weekend I will be able to look a bit more into it, but the wires that are coming through the hole in the dash where the ammeter was missing were added by someone so they need to be traced. thanks for your input, after I get deeper into this I will have more information. And maybe be able to post a good picture of what I am dealing with