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I have been all over the forum and found various answers to this thread but nothing conclusive and no pictures. I'm replacing my 1972 Oil Pressure, Temp, and Ammeter with 1974 electric gauges. The actual wiring is causing me much confusion. From behind the console (looking at the back of the gauge) which wires go where? On the temp gauge there are four posts (looking at the gauge from the rear) north, south, east, and west. Which is the sender, the ignition, and the ground, and which one should be left empty? On the oil gauge, which one is the sender and which one is the ground (east or west). On the voltmeter (not an ammeter) "see my pics", which one is the sender and which is the ground - [east or west] - (it's a three post gauge), and should the 6`oclock brass post remain empty or grounded? I'm having to run some new wire and can't seem to get my Voltmeter to read. All the others seem to do ok but I would like to double-check with you pro's out there. I'm going to post a little Pain picture, feel free to grab it and scribble on it, and repost - I could really use a little help. Thanks in advance.
Ooops. my bad ... the oil pressure gauge only has three posts, and east, west, and 6`oclock south.
Last edited by mitch.1972vette; Oct 15, 2020 at 08:09 PM.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Does this help?
I still have an AMP meter so go by Mooser's post.
Both of the AMP wires are hot and ( you need only one and tape off the other) I don't know which wire you should use.
Last edited by Peterbuilt; Oct 15, 2020 at 07:24 PM.
Reason: This is from my '74.
I'll add that since the amp meter wiring is weird (not like a straight amp meter) tape off the ends and run a new positive (switched) and ground wire. You could also find a 12v source to tie into back there like the water temp
M
You do need to change your ground- to the copper post.
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edit- my pic is how to wire the voltmeter in the oil press position-
Need to see the conversion- electric oil pressure gauge to figure correct wiring for it
Last edited by Richard454; Oct 15, 2020 at 07:56 PM.
BTW, you should be able to confirm the posts on the gauge with a couple of flashlight batteries (I think 3v at least showed on mine) rather than risking damage with a full 12v car battery
M
You do need to change your ground- to the copper post.
**************************************** *************************************
edit- my pic is how to wire the voltmeter in the oil press position-
Need to see the conversion- electric oil pressure gauge to figure correct wiring for it
Actually, the gauge in the pic is the oil pressure gauge. I'm sorry for the confusing photo, I had the voltmeter out trying to bench test it. Your arrows are appreciated and help me understand what I was doing wrong with my ground. That confirms what Mooser has posed as well. On the "temp gauge", the black/white wire seems to come from the horn relay but it's kinda hard to tell for sure. If that's the case, would it be good to use this on the sender (ohm) side and ground the temperature gauge with the brass post? Or, would it be better to run a new wire to the horn relay? Thank for all the help folks, it's very much appreciated.
You could use either ammeter wire to feed + voltage to the new voltmeter. Both of those wires connect to the same primary power wire in the engine harness. The only difference in them is the 18" of primary harness wire between their connection points. That length of wire was used as a current shunt to obtain signal for the ammeter. [Long story and you don't need to know the details since your are junking a perfectly good ammeter...]. Just pick one of those two wires and hook it up to the + terminal and connect chassis ground to the other. Done.......
You could use either ammeter wire to feed + voltage to the new voltmeter. Both of those wires connect to the same primary power wire in the engine harness. The only difference in them is the 18" of primary harness wire between their connection points. That length of wire was used as a current shunt to obtain signal for the ammeter. [Long story and you don't need to know the details since your are junking a perfectly good ammeter...]. Just pick one of those two wires and hook it up to the + terminal and connect chassis ground to the other. Done.......
No, you can't. It would let the meter measure battery voltage, but neither wire is switched so using either would cause the volt meter to drain the battery.
Last edited by lionelhutz; Oct 18, 2020 at 10:45 PM.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi again.
Originally Posted by lionelhutz
No, you can't. It would let the meter measure battery voltage, but neither wire is switched so using either would cause the volt meter to drain the battery.
Thank you for that information in case I ever change to a voltmeter.
We both have merit to our respective posts: you CAN use either ammeter wire to send voltage signal to a voltmeter; AND it would be best to use 'ignition-switched' 12vdc instead of battery-ready 12vdc.
I sure appreciate all the help. Unfortunately, my new gauge failed the field test with a 9-volt battery. I installed the gauge for grins and giggles using both methods offered above only to discover the gauge would not read over 8.5-9 volts. It's going back to ZiP for an exchange. A bummer none-the-less. All the other gauges are reading properly. I finally got to drive the car again this week and it was a blast. Looking forward to finishing up my projects so I can spend a little more time with it.... I recently installed a CVR Vacuum Pump and was wondering if I could get you folks to look over my diagram - kinda critique it and let me know if you think it will work. I'm currently running everything off the electric pump. The motor has a pretty aggressive cam and I don't think it's creating enough vacuum to amount to anything. I'm going to attach the diagram below:
My volt gauge is reading a max of 8.5 to 9.0 volts ~~~ it's a bad gauge. Going to return it for a replacement. Has anyone retrofitted an O2 or Air fuel meter in the place of the factory clock? That's what I'm considering but don't want to use a meter that's only good for a year or two - I would like to use a gauge that is proven to be reliable, any suggestions? I know it's off-topic but could resist asking
Running the AEM one. Had thought AEM brand was a "ricer" cheap one- but I was wrong!!! It works great. No calibration- just hook it up and it works.
I tried an Innovate one- - more expensive- had to keep re-calibrating and it then just quit working. And looking around on line- was not the only one disappointed with innovate.
Also bought AEM fuel pressure gauge- no problems at all and very accurate.
Running the AEM one. Had thought AEM brand was a "ricer" cheap one- but I was wrong!!! It works great. No calibration- just hook it up and it works.
I tried an Innovate one- - more expensive- had to keep re-calibrating and it then just quit working. And looking around on line- was not the only one disappointed with innovate.
Also bought AEM fuel pressure gauge- no problems at all and very accurate.
Richard
Thanks Richard, is it by chance this one AEM Electronics Wideband Air/Fuel UEGO Gauge Kit 30-4110, or did you choose another one? Please share if you have found a reliable gauge. I too have scoured the internet looking for a gauge that would be good for day to day driving and come up with a lot of mixed reviews.
Finally.....believe it or not, I will get to put your electric headlight kit in my car this week!!! If my health will hold out just a little bit longer I will get to see the headlights come up together instead of that lazy eye-thing..lol..
74 Volt Gauge Bench-Testing
