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As I am getting way to old to be laying on the interior floor trying to work on wiring under the dash and my Autometer Trans Fluid Temp Gauge needs a keyed 12 volt source where is a easy pickup point in the engine compartment? Can I use the (+) connection on the coil? Better keyed place?
I would not use the ignition wire. It is actually not 12volts. There is a resistor inline and it drops it to about 9v.
I know it's under the dash, but I would look for the radio wire. That is keyed 12v. There is no real easy 12v keyed source under the hood, except the regulator for the alternator.
Is the gauge digital? Or is it just for the light?
You can also buy a copper ring to install for a glass fuse that gives you a spade lug for additional circuit. Pull the radio fuse, install the ring and hook the wire on. A parts store should have something in the electric aisle. That might be a bit easier then finding the radio wire.
Follow the hot wire from the fan, which is by your passenger feet and should be exposed. I may have had to take out my glove box lining, but I did it all from my passenger side and it wasn't terrible.
Well I have added a 3 gauge setup to the bottom of my dash unit. I did not want to cut holes in my stock dash. I was going to remove existing gauge cluster to get my OEM amp meter & odometer working but my health has not been good lately so I have made a few additions to my gauge setup. Also wanted a trans fluid temp gauge for my new rebuilt C4.
I installed a 3 gauge setup with a volt gauge, trans fluid temp gauge & a GPS mph/odometer gauge. Took a short test run and GPS showed 16 miles like it was, Volt gauge was reading 13.5 volts and trans fluid temp gauge go up to 155 degrees with no load. When we rebuilt the C4 trans we also upgraded the fluid cooler to a HD unit.
Very happy with the operation of the new gauges. Not the cleanest setup but it will be fine for now.
I ended up getting a keyed power source by using the top fuse in my OEM box, it is a 30 amp for Heater / AC and I have no AC and only heater fan. I made the connection with a copper sleeve on the discharge end of the fuse with a spade connection that "Freightrain" posted with a picture, it worked out real fine and the 3 gauges draw only a few amps for light & operating power.
