My 71 Cutlass came with an older triple gauge set which includes an Ammeter. I am looking to upgrade the gauges to nicer Auto Meter ones. The wiring to the Ammeter is quite thick. When I disconnected the wires the car would not turn on. I have zero knowledge on matters electrical and what I have researched so far is that an Ammeter is wired into the circuit. It appears that the wires trace back to the lines going to the battery. So to get the car going, I have reconnected the wires to the back of the Ammeter.

Am I correct in assuming that:

- voltmeter would NOT be hooked up to the same electrical wires going into the Ammeter? The Voltmeter from my understanding can be wired to the accessory in the fusebox + a simple ground - very different than Ammeter as it runs parallel not in circuit.

- Can I connect the two leads going to the Ammeter together and close the circuit or would this cause some sort of issues?
OR
- Instead of just joining the wires going to the Ammeter - can I use these wires to add a Kill switch to the system?

Thanks in advance.

 

Ammeters have fallen out of favor because except for the starter wiring, EVERY circuit in the car has to run through the ammeter for it to be useful. Yeah, if you disconnect the meter, there will be no power to the car unless you wire those two wires together. No, you cannot simply connect a voltmeter in the same place. The fireworks will be dramatic but short-lived, however the ensuing fire will likely go on for a while. The ammeter is wired in series with the rest of the electrical loads (in line). The voltmeter is wired in parallel.

 

An ammeter does not have the full load of the cars electrical system running through it, it's wired on its own in parallel to the cars load similar to the drawing below. You can us 1 of the 2 removed ammeter wires (remove the other) and a ground to power a volt meter. You cannot use the ammeter wiring for a kill switch.

 

You have no idea how his aftermarket ammeter is connected, but the fact that there is no power in his car with it disconnected kinda proves that at least all the critical loads go through it. Back when cars had 37 amp alternators, this was not a problem. Today it obviously is.

 

Thanks for the replies. Given that I cannot wire a Kill Switch and I am unable to figure out how to trace the cables and delete the circuit, I will just connect the wires on the Ammeter together (closing the circuit) and leave them be. I want to avoid damaging any electrical components or worse, torching my Cutlass.

 

I had a similar "Incident". I bought a car recently which had an ammeter, it seemed to work fine.
Some previous owner had painted the alternator black, and worse than that it was an awful paint job. I had a rebuilt alternator that had never been used, in the box, same size/amp. So I replaced the black blob with the rebuilt one. The ammeter went silly, the needle just started whipping back and forth at a very high rate, and didn't stop.
So I had a new (but old, just never used) 3 gauge panel, I took the instruction sheet out and read how to hook up the ammeter. It said to run all the power through the meter! I thought BULL SHxx, no way. I looked things over and it indeed had 2 big wires going to the meter. I got under the hood to see where this thing got it's power. The guy had interrupted the alternator wire, added wire the same size as the factory alternator wire and ran it through the ammeter. Luckily he had NOT cut the factory wire end off but used a bolt to connect the wire which went to the ammeter, so I just hooked it up as it was when new and all worked well.
Well almost all good, the "ALT" red light on the dash doesn't work, checked the bulb, bulb good, but no workey. I will have to look deeper to figure it out.
But the car is fine as is, all working except ALT light.
I would NOT have another ammeter, not needed anyway. A red light is fine for monitoring the charging system, for me.

 

That would work but is not really the best way as it leaves a lot of "hot" wires that could cause issues.

I would look near the horn relay / junction block to see if the ammeter wires are connected there. My car is wired that way - I disconnected the heavy gauge wire from the stud on the junction block, ran two wires from the ammeter to that point, connected one wire to the end of the disconnected wire, and connected the other wire (through a fuse) to the stud on the junction block. Very simple to connect and also very simple to disconnect.

 

Joe you are correct, I zipped through this originally as I was out getting ready for a CT Scan and replying on my phone. I missed the part about the no power in the car with it disconnected.

To the OP, sorry about that. However good news, you can use those two wires with a heavy duty disconnect switch if you like. If it were me I would return the wiring to a somewhat stock configuration.

 

I would much rather remove this set up all together as suggested. What I gathered from tracing the wires (although they seem bunched up and colors change throughout the wiring)

There is one red/yellow wire connected to what I believe to be the Horn Relay or some sort of relay on the fender and One black wire going to the positive of the battery terminal. Would ths seem likely?

Pictures for reference:

 

I have connected the two wires for now to complete the circuit. Given the connection exists, im inclined to install a kill switch. What amp switch would be recommended given that the entire car's power goes through these wires? Any suggested brands/type of switches?

 

Try leaving the ammeter wires disconnected and run a 10ga jumper from the pos battery cable to the horn relay.

 

Get rid of the wires running into the car interior. They carry too much power. Here is what I found when I bought my car recently. Scared the hell out of me. A cheap little switch was used as a kill switch for the whole car. Wired into the line from battery to horn relay junction. 1971 Cutlass. The large fuse is a separate sound system. The terminals on that little switch were melted. Get the wiring out of your car for safety. From what you describe, it sounds like you should disconnect the wire at the battery running to the ammeter, & also disconnect the wire from the junction block at the horn relay running to the ammeter. Then all you need is a 10 ga wire from the battery to the junction at the horn relay. I'm sure someone else will jump in & verify this.

 

Get the ammeter out of the car and put in a voltmeter. Much more useful information.

 

I wouldn't say it is much more useful, it is just a different measurement. If I had an ammeter and a voltmeter in my car, then I would have enough data to know exactly how my charging system was functioning. Having one or the other gives partial information. Here at work we use both to analyze failures as one or the other doesn't provide the full picture.

 

I replaced the ammeter with a voltmeter. Technically at the moment I had both running but took out the ammeter and connected the two wires. I could just leave the ammeter hooked up and move it under the hood

Or just cut the wires shorter and connect them under the hood vs. having them in the connected under the dash. It appears that one lead goes to the horn relay and one to the battery positive terminal but again. Based on what Im understanding I cannot just remove the two wires. The circuit would remain incomplete as the car doesnt have any power when both wires do not touch....

I am also interested in wiring a kill switch if possible as I live in the City (Toronto) and car thefts are uncomfortably high.

 

All you need to do is connect the battery to the horn relay junction, to complete the circuit as in the original car. 1971 Cutlass.