help with wiring!! I'm at the end of my patience here

[ian8950 2]

Hi everyone, I have a 1969 Fastback and I am installing a set of autometer gauges to replace the worn out original set, including adding a tach. The gauges that I am using are the American Muscle set and include: Voltmeter, Oil Pressure, Water Temp, Fuel Level, Speedo and Tach. I am running into all sorts of problems and could use some help. I am currently using "Painless Performance #30302" wiring harness for easy connections (http://www.summitracing.com/parts/prf-30302) and I am having problems,  any input here would be greatly appreciated. Here's my list of problems;

 

1. Programmable fuel level seems to be most accurate on the GM setting for some reason, not really an issue just super annoying.

 

2. Voltmeter has no reading.

 

3. Dash lights. !@#$ing Dash Lights. ok, so the voltmeter and oil pressure lights are always on. When the car is not running but the headlights are on all the gauges but the voltmeter and oil pressure are lit up. With the car running and the lights on all the gauges stop working completely. This is my biggest issue I am worried that I am damaging something and need it fixed asap.

 

The painless wiring harness set that I'm using has all the wires for the gauges running together, so 1 ground, 1 power etc. Should I pull this thing out and light it on fire and run individual wires or can this setup still work? If I pull it out can I run all the instrument lights to one wire and wire it to the headlight switch? 

 

Also, if anyone has a diagram regarding the stock colored wires and their individual purpose that could be a big help, all the diagrams I have located don't agree on colors, if anyone has a link it would be greatly appreciated.

[Punisher 8]

that kit you got is nice, but needs labels.

 

2. if the voltmeter has no reading, you are either A.) getting no source voltage to the gauge ( it might be hooked up to your light terminal, hence the reason it is on) or B.) bad gauge. But with all your issues, its most likely wiring. in order for the gauge to make a reading, it needs a signal (12V from battery) to the signal terminal on the gauge.

 

3. are your volts and oil lights ALWAYS on? like when the battery is connected and the key out of the ignition? if so, you have a hot wire going to them, meaning a wire that sees source voltage at all times going to it. You need to use a ohmmeter and check for continuity from the wires coming off the headlight switch to your wires going to your gauge lights. you have something hooked up wrong. I would personally run individual wires. if you run all the lights to 1 power wire, they might be dim. use the V=IxR method. Volts = I(amps)xR(resistance) . if your bulbs each have a resistance of 2 ohms(you must check for resistance while the bulbs are on as the resistance value will change) and your on a 12v circuit, with 6 bulbs, that would be 2 ohms X 6 bulbs=12 ohms of resistance. that means you have 1 Amp flowing through that circuit. lights would be dim. but if you use 1 bulb at 2 ohms on a 12v circuit, you would have 6 amps running through that circuit, which would be nice and bright, but also would blow a fuse that was a 5 amp fuse. so it depends on your wiring setup.

 

I would personally just rewire everything to my liking. I run individual switches/relays/fuses for all my circuits/systems.  ill post a picture of my wiring. I hope this helps a little.

[Punisher 8]

 

[Rsmach1 71]

X2 as Punisher said, start over and label your wires.

[ian8950 2]

Thanks for the help guys, I was really hoping that I wouldn't have to start over, it's such a headache. I'll give it a try this sunday and post if I can get it to work

[fordguy69 24]

Punisher, your wiring is freaking art!  I wish I had the ability and patience to do it like that.  Well done.

[ian8950 2]

does anyone have a schematic for the in dash wiring for what wires power what? The only one's I've been able to find online are unlear and list multiple grounds for each gauge and no sensor inputs. I am figuring it out as I go but knowing what does what will be a GREAT help

[magician 13]

Why do you need factory diagram if you are running a painless harness?

[Punisher 8]

Punisher, your wiring is freaking art!  I wish I had the ability and patience to do it like that.  Well done.

Thanks man! yea it takes a ton of patience. it helps when you have to wait on car parts to come in, that or I would do a lot of it while in front of the tv and drinking a beer, then just transfer my work to the garage lol

[ian8950 2]

I have another question,  all my gauges work and light up with the lights on and the car not running, as soon as I start the car they turn off (gauges stop working and lights turn off.) what have I done wrong? I'm thinking that one wire running to all the gauges powering them is overloading it, what other wire can I wire the lights to?

[Rsmach1 71]

Question, if you disconnect the wire for your gauge lights and start the car do your gauges work? With your headlights on? with them off? How did you ground everything, to an existing wire or directly to the body?

[ian8950 2]

the gauges work if I disconnect the gauge lights, and I used the existing ground wire. with the lights connected when I start the car both the dash lights and the gauges turn off when I turn on the headlights. However with the headlights on and the car not running the lights and gauges work fine.

 

so..

 

car not running and headlights on= everything works

car running and headlights on= nothing works

car running and headlights off= gauges work and volt meter/oil pressure lights always on. 

 

I'm so confused.

[Rsmach1 71]

OK first it's best to ground directly to the body rather then to an existing wire. Secondly if you are getting lights on 2 gauges with the light power wire disconnected you have wired something wrong, that's where you need to start. Check the light wires to those 2 gauges, how are they getting power with the main light power disconnected?

[ian8950 2]

ok, I remade my own ground instead of using the existing one. Now everything seems to work, and I redid a lot of the connections and the gauges are only powered when I want them to be :) Thanks for the ground tip RSmach1

 

one last question though, I have installed a one wire alternator (140amp) and I am unsure what to hook up the volt meter to. It was originally going to the regulator but the new alt is internally regulated. Can I run it off my electric choke since that only runs in key on position?

[ian8950 2]

ok, another problem, while the gauges are working and lit up, only two of them are bright and the rest are super dim. What can I do to fix this? Should I run individual wires for the gauge lights, and if so to where? They are currently running all together to the single dash lights wire originally used in the car.

[Rsmach1 71]

Second question first, dbl check the connections on the dim gauges, specially grounds, where are you getting the power source for the gauge lights? Are the dim lights on the same 2 gauges you had a problem with being on all the time?

 

Edit Did you find out how the 2 gauges were getting power to the lights with the power wire disconnected? or did you just fix the ground? If you just fixed the ground they are probably shorting.

[SA69mach 39]

what is the fuel gauge ohm range?

It should be in the instruction/specification paperwork, or stamped on the gauge itself.

If your fuel level is not accurate, make sure your sender and gauge are a match for ohm (resistance) range.

Ford stock senders for temp oil pressure and fuel are all 10 ohm - 78 ohm. Your gauges must match. GM and Mopar are different, and it is possible you have a mismatch. It is also unfortunately a common issue with the Mustangs to have bad senders, especially fuel senders.

 

I know this is not the primary concern for you at present, but when you have your power feed and grounding issues sorted out with the new gauges, it will be your next issue to make sure they are accurate.

[ian8950 2]

ok, I've got almost everything working correctly. Here's what I did;

 

re calibrated the fuel level gauge for the 73-10 ohm rating for pre '89 fords and that works fine now.

actually took apart the "painless wiring" harness and found that 2 wires were crossed inside, halfway through the harness the colors changed from red/white to brown for power and lighting only on the voltage and oil pressure gauges. Switched those out and now everything works good. I still need to switch out my oil sender to get accurate readings on the gauge but so far everything seems to be working fine now. Thank you for all the help guys