68 gmc electrical - Antique Car Talk


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68 gmc electrical

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Anonymous Poster
tjbishoff@hotmail.com

Jun 18, 2007, 10:51 PM

Post #1 of 4 (3713 views)

68 gmc electrical	Sign In

I'm changing the generator on my 68 to an alternator. I would like to know if I can change the gen light to an amp meter and how to change it over. Also can I change the temp light to an temp gauge?

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 19, 2007, 5:17 AM

Post #2 of 4 (3708 views)

Re: 68 gmc electrical	Sign In

TMK you have an alternator. The light still says "GEN" and GM did that for a while and those used an external voltage regulator on the firewall usually. They work fine so I don't know why you want to change it. If you want to add a volt meter you could by just tapping into just direct battery power. I find volts is as handy as amps because if it can stay in normal ranges the amps are ok in most cases.

The temp gauge could be added where the switch is for the light only right now or if there is a plug to coolant unused right now you could use that.

They used to make fairly univeral gauges for this and certainly do now. They used a standardized size round gauge and made hoder's for these that could be placed under dash or where you have a good spot. Stewart Warner was big into this and the street Rods still add gauges here, there or wherever for volts/amps, temp, and oil pressure,

T

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Anonymous Poster
tjbishoff@hotmail.com

Jun 19, 2007, 9:43 PM

Post #3 of 4 (3706 views)

Re: 68 gmc electrical	Sign In

thanks for your info tom. I will give you more information.I've install a 1972 dash with an amp gauge in it,as well as an temp gauge. I tried to hook the amp gauge in series but when I turn on the headlights the gauge discharges to the pin.Tried off the alternator in the ignition circuit and battery with no success. Wondering how it needs to be wired in? Or is there a different amp meter I should be using.Does the temp gauge also need to be wired different.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 20, 2007, 6:00 AM

Post #4 of 4 (3703 views)

Re: 68 gmc electrical	Sign In

68 and 72 wiring should be about the same. I have nothing but some generic diagrams and don't even have a scanner to get them into this computer or to this site.

Know that with the external regulator some things are funky. You may need to get a new one. Still available new as far as I know.

The alternators use a diode trio and will charge when one is blown but only about 10-20% of possible power and used to give a dim "GEN" light that might go out with some RPMs. That trio can fail with just messing with the wiring -- I know that.

I can't help much more with specific ways to change this for you. If you can get your hands on about any 68-72 diagrams that would help. There on the web somewhere but I wouldn't know where to start looking. Too bad I threw out a complete set of books for an Olds 88 for 1968 that listed every screw in the car and diagram.

All this stuff exists I just don't know where right now. You could wing it with just generic ways to hook these things up as I don't think they were unique to just GM but who knows now.

It's of interest so let us know if you have any discoveries with this.

Funny: I still deal with a 1948 generator set up as 6V pos ground. Talk about a mind game to figure that sucker out. It's OE amp gauge still works and is manually regulated by a lever/switch for high and low rate of charge. Those were a nightmare back when and still are when anything goes wrong.

Good luck - keep us posted,

T

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