Tachometer Wiring Questions

Hello,

I did some searching here as well as the internet and I'm not finding a complete answer. I have a 1969 base model convertible and installed a small (2-3/8") Bosch tach on my column so I can see how the rpms and transmission are interacting. My question: Is it ok to splice into an accessory circuit that comes ON with the key? The instructions say "no" but I'm not sure if that is because of a chance for radio interference. I tested this connection and the tach works fine (accurate).

I've been probing under the dash (my back really hurts) but I cannot find a dedicated circuit (ON only with the key) that I can splice into. If someone could point me to a wire, that would be great. I have a Chilton manual and have looked at wiring diagrams but I must be to dumb to read it correctly.

The previous owner had wrapped the electric choke wire around the actual fuse. I assume that's not good. Again, I need a circuit that comes on with the key...

Any help from my mustang comrades is appreciated!

In case anyone comes across this in the future, I ended up wiring the tachometer and light into my accessories (radio). I don't know why the Bosch instructions advise against it. Maybe when the radio is used there will be some sort of interference?

The installation came out looking very good. I attached it to column using a 2" rubber plumbing adapter. This can be be found at Home Depot and comes with the necessary hose clamp. I just had to cut excess rubber away to make it proper fit. I routed the wrapped wires through the dash plates/covers where the column goes through. I had to drill 1/4" holes for this and it looks good, with minimal alterations. I pushed the tach signal wire through the firewall where the main harness goes through. The tach seems to work well and accurate but I haven't tested it with the radio on.

Overall, its an easy install. Now I have mount/install mechanical oil pressure and water temp gauges.