Changing an Amp gauge for a Volt gauge

[HusseinHolland]

1 hour ago, Captain Obvious said:

If everything else is accounted for, then I would also assume that 6-position connector is for the radio.

There are five wires leading to the original radio:

• The red/blue and green/white are for the illumination lamp inside the radio.
• The white and white/black go to the speaker, and
• The blue wire is hot when in ACC and ON. Note that power wire goes dead during cranking, so when your voltmeter shuts off while you are running the starter, that's why. 

Also note that same blue wire also supplies power to the rear defogger switch and the antenna switch. So you could verify you've got the right connection by confirming that it's tied to those other two items.

And....... One last thing to talk about. You mentioned earlier about a wide band? That meter system may draw significant power (because of the sensor heater?) and you might not want to pull power for that meter off the same place you put your voltmeter unless you are sure you've got a rock solid clean connection all the way back to the source. I'm thinking the current draw for the sensor may affect the voltage reading. Your voltmeter draw will be negligible, but your wide band may not be.

Thank you for the reply - those colors correspond to the connector in question.

I would rather the Voltmeter be on a circuit that shows the state of the battery, than on a circuit that is subject to transient changes, so I need to check that.

The AEM WBO2 controllers do not draw much current (from the manual):

 

 

EDIT -  I do have another couple wiring questions - these two sets of wires are also in the center console area. 

 

and this unused 6 pole connector is next to the ignition terminal block

any ideas as to the purpose? I'm wondering if I can repurpose the 4 wires in the 6 pole connector, but I have no clue what circuit they belong to 

Edited August 28, 2023 by HusseinHolland

[Yarb]

If those are near the passenger side shock tower I believe they were for the factory AC system. Something to do with the vacuum solenoids/vacuum bottle. My 78 has them and they were not connected. Had the same mess you are dealing with.

[SteveJ]

7 hours ago, HusseinHolland said:

and this unused 6 pole connector is next to the ignition terminal block

any ideas as to the purpose? I'm wondering if I can repurpose the 4 wires in the 6 pole connector, but I have no clue what circuit they belong to 

Test port for the BCDD. Look on page EC-6 of the 76 FSM

[SteveJ]

7 hours ago, HusseinHolland said:

Thank you for the reply - those colors correspond to the connector in question.

I would rather the Voltmeter be on a circuit that shows the state of the battery, than on a circuit that is subject to transient changes, so I need to check that.

The AEM WBO2 controllers do not draw much current (from the manual):

Clock power (as I mentioned in my first response) and cigarette lighter power.

7 hours ago, HusseinHolland said:

EDIT -  I do have another couple wiring questions - these two sets of wires are also in the center console area. 

R/L & G/W - lighting (gauge lights, etc.) The T connector is probably for the HVAC panel. The bullets correspond to the indicator lamp for AT models

[HusseinHolland]

2 hours ago, SteveJ said:

Test port for the BCDD. Look on page EC-6 of the 76 FSM

Thank you Steve, found it! Also used for spark advance/retard (that I don't have). I'll leave those alone for now.

 

2 hours ago, SteveJ said:

Clock power (as I mentioned in my first response) and cigarette lighter power.

R/L & G/W - lighting (gauge lights, etc.) The T connector is probably for the HVAC panel. The bullets correspond to the indicator lamp for AT models

Going to have to memorize the wiring color convention translation 🙂

Clock & Cig lighter (LW = Blue/White) appear to be constant (30) vs. switched (15) power sources, so neither would work for the 3-pod gauges (WBO2 controller, Oil temp, Volt) I'm adding.

OK with those (Red/blue Green/white) wires, all four were bundled & taped inside the harness conduit, so I assume they all go to AT related indication. So, I presume I could repurpose those for gauge illumination, looking through the illumination wiring, they do not appear to be conditional upon other parameters.

[SteveJ]

If you're looking for a switched source that isn't going through a relay, that would be the B/W (On and Start) or L/R (Acc and On). Neither has terminations near the center console. You could get a set of male and female 6 pin 6.3 mm connectors from Vintage Connections and get the power from the back of the switch. I would advise fusing it as close to that connector as possible.

[Captain Obvious]

Yup, that color pair of red/blue and green/white are used pretty much universally throughout the dash and console as illumination lamp power. The red/blue becomes hot when the headlight switch is turned to the first position, and the green/white is pulled to ground through the brightness control knob pot.

The wires you found there could be for the A/T gear lever position illumination and/or for the ash try illumination bulb. Don't remember offhand if they had that yet in 75. In any event, they are dash/console illumination.

[Captain Obvious]

Actually, taking a closer look at your pics, it looks like the white two position connector includes a red/GREEN, not red/blue. And if that's the case, then the wiring diagram indicates it was for the fog lamp switch. Optional for other countries, I think.

[HusseinHolland]

12 hours ago, SteveJ said:

If you're looking for a switched source that isn't going through a relay, that would be the B/W (On and Start) or L/R (Acc and On). Neither has terminations near the center console. You could get a set of male and female 6 pin 6.3 mm connectors from Vintage Connections and get the power from the back of the switch. I would advise fusing it as close to that connector as possible.

Thanks Steve - as far as I can tell, everything has to come through the Cx connectors. I would pull from there before adding load to the ignition switch. I have a good supply of 6.3mm crimp terminals & housings - both Volvo and Fiat used them back in the day 🙂

My main issue is the Nissan wiring diagrams make zero sense to me - I can't read the connector pinouts for the life of me. I'm assuming what's shown is either side of any given connector - C-2 in this case. Can't tell which side is body & which is harness. I'm used to diagrams that indicate the pin numbering - since this is 14pole - the diagram (for Volvo for instance) would indicate 1-14, so it would be easier to negotiate the diagram & corresponding harness wires/colors. It's gonna take a while to get used to these.

Edited August 29, 2023 by HusseinHolland

[HusseinHolland]

11 hours ago, Captain Obvious said:

Actually, taking a closer look at your pics, it looks like the white two position connector includes a red/GREEN, not red/blue. And if that's the case, then the wiring diagram indicates it was for the fog lamp switch. Optional for other countries, I think.

interesting - there are wires taped up in the front crossmember /valance harness, I've not examined them, but presumably those would be for fog lamps then. I don't see any mention of them in the 75 FSM though.

Another thing I've found - the harness & bulb holder I've circled seems to be for the low Fuel indicator lamp (yellow/blue , blue) = which I don't have. I'm assuming it was a small square lamp in the console below the radio, but that's where the AC thermostat was installed, so I guess they simply discarded the holder 😞

 

[Captain Obvious]

40 minutes ago, HusseinHolland said:

My main issue is the Nissan wiring diagrams make zero sense to me - I can't read the connector pinouts for the life of me. I'm assuming what's shown is either side of any given connector

Best way I could describe the connector mating:

1) Hold your two hands out in front of you, palms facing up.
2) Then bring your two palms together.

That's how the connectors on the wiring diagrams mate. And as for which side is which... In general, things are laid out on the wiring diagrams like they are laid out in the car. So for the Cn connectors the half on the left is the engine bay side, and the half on the right is the passenger compartment side.

Does any of that help at all?   

As an additional aid on this C-2, the "X" is an unused cavity in the connector shell. That should help show how the two sides go together "mirror like".

For example, the G/L on the far left connects to the G/L on the far right. While the "X" on the left connects to the "X" on the right side.

[Captain Obvious]

And about your fuel lamp, yes... In 75 that lamp was located in the small square location below the radio. In later years, they moved it up to above the center vent outlets in the HVAC panel, but your car (especially since it's a California spec) has those locations above the HVAC populated with other items.

And honestly, it probably doesn't work anymore. Your thermistor in your gas tank probably burned open years ago.