I've got an autometer electric oil temp and oil pressure guage. Install seems pretty simple but I was wondering which ignition wire I should use for these? Also will both work off of the one autometer sender mounted by the distributor?

 

Use the Gauges feed. Should be able to get one of those clippy things that goes under a fuse.

No you can't use the same sending unit. For one thing, it will be specific to the quantity it's measuring: a pressure one (usually a spring-loaded diaphragm kind of thing) will be specifically designed to be insensitive to temperature, and a temperature one (usually a semiconductor substance whose resistance decreases as it gets hot) is totally unaffected by pressure. For another, at that physical place, the pressure one will be quite accurate, as it's exposed to a pressurized oil passage; but a temperature probe mounted there will tell you block temp, not oil temp. An oil temp sensor needs to be in the pan, submerged in the oil sump.

 

What did you mean by guages feed? And clippy thing by the fuse?

 

I mean, the power that powers the gauges. Comes off of a fuse labeled "gauges" or something similarly cryptic.

They make a thing you can plug into the fuseholder, and then you plug the fuse into that. It has places you can attach more wires to.

Pull the "gauges" fuse, put the adapter thingy in, put the fuse back, connect a wire to the fused side of the fuse via the adapter thingy, and run it to your new gauges.

 

ok Ill have to look for that at an auto parts store.

 

Piece o cake.

 

would you be talking about an add-a-fuse or a fuse tap? I came up with those with a Google search. Thanks for the input I had no idea these existed!

 

Yup; that would be the one. Sorry, my brain got a cramp, and it couldn't remember their "name".

 

I ended up picking up a couple but I notice the directions say only good up to a 10a fuse. For aftermarket guages would I need anything more than a 10a?

 

No... really, a 1A would be entirely adequate if such a thing existed. Gauges use VERY LITTLE (emphasis on VERY) little power. Although if memory serves the smallest one you can get is a 3A, which is still like about 10 times as much as the entire instrument cluster really needs, but the wires are much larger than that. All the fuse needs to do is keep the wire from starting a fire if your hookup screws up and a wire touches sheet metal.

 

Sofa- I've got an oil temp gauge I'll be installing when I pull the engine again. Was wondering if mounting the oil temp sensor (via welding a bung) in the oil pan was the better place or just sticking with the extra port on the china wall by the dizzy?

 

If the sensor is up on top of the block, it will measure block temp at that point, not oil temp.

To measure oil temp unambiguously and without interference from anything else, the sensor pretty much needs to go in the sump. If you had a dry-sump system it could go in a line somewhere but putting it in a casting will make it measure the wrong thing.

 

With that being said is an oil temp guage with the sender by the oil filter not that accurate?

 

What will it be measuring the temperature of at that point? An ounce of oil or 200 lbs of cast-iron? Will the temp of that little spot on the block really be even affected materially at all by the oil nearby, let alone independent of the rest of the casting?

The right place for an oil temp sending unit is in the sump or in an external line that is at oil temp not casting temp.

 

One more question- for the 12v source of the aftermarket guages I'm adding, does each need its own source/fuse plug in? Maybe I'm just overthinking this.

 

It is perfectly acceptable to feed more than one gauge from the same +12V power source , since the factory setup feeds them all from that same "gauges" fuse . In fact , were I doing this , it would be the gauges power source that I tapped into for the +12 to feed the aftermarket gauges . As Sofa said , gauges draw VERY small amounts of power to display their readings * and so multiple gauges fed power from the same source is fine .

* The exception being of course that an amp gauge with it's shunt built in must be placed in series with all electrical devices except the starter motor itself and the battery . This was seen very commonly on cars up till the late 60s / early 70s when cars got far too many power accessories to be putting the load through a dashboard mounted gauge . At that point they began monitoring volts rather than amps with regards to the charge/drain status of the battery .

 

Just trying to picture this. What would be the easiest way to go about connecting the 12v wire from each guage (3 aftermarket) into the one guage fuse?

 

Twist the three wires from the gauges together and then twist one more wire into those . Solder the connection and cover it with heat shrinkable tubing (preferable) or electrical tape (if no shrink wrap available) . Now take the other end of that one wire that you soldered onto the three gauge wires and attach it to the fuse tap device that Sofa mentioned and connect that to the "cold side" ("fused side" rather than "feed side") of the gauges fuse . This completes the +12 wiring to your new gauges . All three gauges will have a ground wire which similarly can get connected together , add one more to them , solder & insulate , and connect to a good solid ground . This will complete the -12 volt wiring . It's likely your new gauges will have lights in them , again , twist the three light wires together , connect another , solder & insulate , and connect the other end to the source of power that feeds the dashboard lights , the cold side of the 5 amp fuse called "inst lps" , using another fuse tap device . This way the gauge lights will work with the regular speedo & tach illumination rather than just lighting up whenever the key is on which they will do if you connect your lights feed wire to the key circuit rather than the dashboard illumination circuit . After all that , your last wiring will of course be to the sending units themselves , this is a one wire deal with the engine block providing the sender's - 12 volt (ground) side .

I hope that helps some and if you have any other questions feel free to ask ..