Late Combo Gauge w/ temp ('74) wiring to a '72 Options

[Literati914]

I'm hooking up a late combo gauge from a '74, the one with a temp gauge at the top (914.641.101.50) - into my '72.

I'm a little confused with the brake warning light circuit .. the diagram below shows two BR/YL wires for the M/C (apparently) & E-brake handle switch. The '72 harness has these wires as BR/WH .. so that's obvious. But the '72 also has a third BR/WH wire going to this light from the safety belt switch. So three BR/WH wires to this light socket via a "dual spade connector". Adding these three BR/WH wires at the warning light is again, obvious. But this diagram has no mention of the BK/WH/GR wire that comes from the hazard flasher. Maybe it was accidently left off - or possibly on purpose because the '74 didn't do it that way ? (IMG:style_emoticons/default/confused24.gif) If it's recommended to add it (via a second dual spade connector), which side of the light fixture would it connect to - RD/WH or BR/WH ?

[Literati914]

Actually looking at the diagrams.. I'm thinking that maybe that RD/WH wire going to the warning light in the diagram that I posted ^^ should actually be the BK/WH/GR . I mean neither of the diagrams (early vs late) show a powered (RD/WH) wire going there - they both have the BK/WH/Gr in that place. So, unless haynes is off, that should work - I'll give it a try and see. Feel free to double check me though.

[JeffBowlsby]

No oil temp gauge circuit in a 1972 chassis harness. Run a new wire as needed.

http://www.914world.com/bbs2/index.php?showtopic=372354

[Literati914]

No oil temp gauge circuit in a 1972 chassis harness. Run a new wire as needed.

http://www.914world.com/bbs2/index.php?showtopic=372354

Agreed, I made sure to add the correct GR/BK wire back when I still had the harness out. I have that hooked up at the gauge and it seems to be active, it twitches when the key goes to "on". I haven't hooked it up under the engine yet, 'cause I'll be adding the tuna can and sender at my first oil change after the first engine run. So the temp gauge is covered.

Update - on the brake warning light ... I was right that the BK/WH/GR wire should replace the RD/WH one that the drawing above shows (brake warning light only). I made the swap and got the brake light on now and it's blinking at the "on" position. I suppose that's because I need to re-bleed my brakes after loosing most of the reservoir contents (due to missing washers inside the M/C, which was (IMG:style_emoticons/default/bs.gif) ).

[Literati914]

Electrical Diodes ?

The stock '72 fuel combo gauge incorporated two diodes .. one between the brake warning light and the 'seatbelt & hand brake wiring'.

Then there is also a diode between the generator light and the brake warning light. This is the one I'm questioning.. what's it for? Was it because the stock combo gauge actually had two brake warning lights - and therefore not needed on the later combo gauge that I'm using (w/ temp gauge incorporated)?

Basically, I'd be ok with leaving it out if not needed, but want to be sure it's not a needed item with this late combo gauge. Anyone know?

[Literati914]

Answering my own question here.. after further research, I found some mention along the lines of ‘a missing diode between generator light and brake warning light could cause the engine to not shut off’ or something along those lines. Also I found the following post from @Spoke further explaining the circuit and it sounds like the double diode set up is specific to the ‘72 model and in short is basically a safety net for the generator light burning out. Also, from the description.. it sounds like it may not be a good idea on a ‘72 to run an LED light at the brake warning spot either. Because if the current is too low there it can’t activate the generator light in an emergency. Maybe Spoke can confirm this ?

[Superhawk996]

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