45 Ahmeter Swap With 280Z Voltmeter/ Fuel Gauge On A 1972 240Z

[jalexquijano]

I am planning on replacing my - 45 --- +45 original ahmeter / fuel gauge installed from Factory in my 1972 240z with a used 280z voltmeter / fuel gauge. The purpose of doing this is because it is not working and could be damaged. The fuel section does work perfectly. Anyway i have several questions:


1. If i decide to change the alternator to a High Output 125 amp alternator if it was not damaged will it still work as i have a spare 45 ahmeter? Right now it has a Bosch 60 amp alternator.


2. Will this upgrade of a 280z voltmeter affect the originality of the car? Value of the car?


3. Will i need to make some modifications to the circuit or is it just plug and play with the current 60 amp alternator or with the coming 125 amp alternator?


4. If i decide to purchase this voltmeter i will need to paint the face. What kind of black spray paint will i need?

[Jehannum]

2) anything you do to the car affects the originality.  I don't know about value (I'm not planning to sell mine).  WRT aesthetics, there was only one model year cluster that had the same font for the voltmeter as the ammeter (the actual year escapes me at the moment, sorry).  You can swap the gauge faces from your old fuel gauge onto the 280Z unit to keep the gauge face font correct for that one.

 

3) before modifying the circuit, you need to swap the guts of the 280 gauge into the housing of the 240 gauge - the mounting scheme is different.  After that, splice the R/W and W wires together with an additional small 18ga pigtail, insulate the everloving crap out of the junction, connect the pigtail to the + terminal on the voltmeter, then connect the negative terminal to ground.  Reassemble, you're done.

 

4) You shouldn't need to paint the face, if you swap the gauge from a 280Z.

[jalexquijano]

2) anything you do to the car affects the originality.  I don't know about value (I'm not planning to sell mine).  WRT aesthetics, there was only one model year cluster that had the same font for the voltmeter as the ammeter (the actual year escapes me at the moment, sorry).  You can swap the gauge faces from your old fuel gauge onto the 280Z unit to keep the gauge face font correct for that one.

 

3) before modifying the circuit, you need to swap the guts of the 280 gauge into the housing of the 240 gauge - the mounting scheme is different.  After that, splice the R/W and W wires together with an additional small 18ga pigtail, insulate the everloving crap out of the junction, connect the pigtail to the + terminal on the voltmeter, then connect the negative terminal to ground.  Reassemble, you're done.

 

4) You shouldn't need to paint the face, if you swap the gauge from a 280Z.

Okay,

 

So its better to keep the original 45 ahmeter gauge. Will the Reading be affected if i replace the 60 amp alternator with a 125 alternator???

[Jehannum]

Okay,

 

So its better to keep the original 45 ahmeter gauge. Will the Reading be affected if i replace the 60 amp alternator with a 125 alternator???

If it's internally regulated, it won't matter, because the ammeter won't read correctly anyway.

[munters]

If you want to make your own plate, I made a Windows font with all the relevant letters and numbers.

The font will be called 240Z after you installed it (just unzip and double click...)

Or use my jpg or dxf

240Z.zip

AMPPLATE5b.dxf

Edited March 26, 2015 by munters

[jalexquijano]

i think ill stay with a 45 amp gauge, even though i actually havea 60 amp Bosch internally regulated alternator! Can someone point out how shall it read,if the ahmeter is working correctly?

[S30Driver]

I think i understand where your confusion with the Amp gauge is.

It measures total current flow in the circuit it is on, either charging or discharging.  Assuming nissan made it an accurate ammeter gauge, it can read up to 45 amps of total current draw in either direction.

Unless you install many more accessories, like a set of 4 super oscar driving lights, and 4 more stereo's with amplifiers, with your 60 amp alternator the car will never draw more current than the gauge can show.

In other words, you could install a 200 amp alternator and the gauge would be fine, because the cars electrical load will never come close to that.

 

The bigger capacity alternator will just have an easier time keeping the voltage up and the current low for the given load.

 

Hope this helps.

[jalexquijano]

I think i understand where your confusion with the Amp gauge is.

It measures total current flow in the circuit it is on, either charging or discharging.  Assuming nissan made it an accurate ammeter gauge, it can read up to 45 amps of total current draw in either direction.

Unless you install many more accessories, like a set of 4 super oscar driving lights, and 4 more stereo's with amplifiers, with your 60 amp alternator the car will never draw more current than the gauge can show.

In other words, you could install a 200 amp alternator and the gauge would be fine, because the cars electrical load will never come close to that.

 

The bigger capacity alternator will just have an easier time keeping the voltage up and the current low for the given load.

 

Hope this helps.

Thanks S30 driver! You hit the nail on my query! Last query i have is the following:

 

I am planning on installing a Sanden 508 compressor with the Vintage Gen II mini evaporator kit which i already bought! Is it recomendable to upgrade to 125 High Output Alternator? Will i need to do any modifications to the Ahmeter gauge?

[Jehannum]

Thanks S30 driver! You hit the nail on my query! Last query i have is the following:

 

I am planning on installing a Sanden 508 compressor with the Vintage Gen II mini evaporator kit which i already bought! Is it recomendable to upgrade to 125 High Output Alternator? Will i need to do any modifications to the Ahmeter gauge?

Unless you're running your compressor with an electric motor, you should be just fine with whatever alternator (even stock 45A units ran plenty of air conditioners back in the '70s).  The only current draw above and beyond stock for those is the compressor clutch.

 

And seriously, you're gonna drop an aftermarket aircon in, but you're worried about the originality of swapping a voltmeter in place of an ammeter?

 

The voltmeter is a much more useful diagnostic tool to have.  FWIW, after I swapped a ZX alternator into my Z, the ammeter constantly read slightly less than 0.  This makes no sense in context, unless the battery wasn't charging, but it was, so I posit that there's something about the ZX alt swap that makes the ammeter readings suspect.

[jalexquijano]

Will it the 60 amp alternator give me hassle once the AC system is installed?

[Jehannum]

Will it the 60 amp alternator give me hassle once the AC system is installed?

No.