I just installed a Hobbs meter in my 1999 F350. General steps to do this are,

1) Acquire a 12v Hobbs meter suitable for this application. I got mine on eBay for $12.
2) Mount Hobbs meter in desired location. Below photo shows unit mounted in an unused area of the dash bezel. The hole was cut using a Dremel tool.
3) In '99-'01 F350/250 locate circuit 295 (LB/PK), later trucks use Circuit 294 (WH/LB). This is the power take off circuit. Attach this wire to the positive terminal of the Hobbs meter. Google for further information about wiring.
/********************************Warning*********** *************
* My truck had a stubbed off wire taped to the OBD plug labelled
* "Power Take Off Circuit". This did not have power in key-off,
* key-on, or engine-on states. This is a light blue wire w/a
* light green (possibly white?) trace. Further up the bundle
* was found the stubbed light blue wire with a red (or pink)
* trace. This wire has power in key-on and engine-on states.
* The wire was assumed to be circuit 295 and was used.
*******************************end Warning**********************/
4) Run a wire from the negative terminal of the Hobbs meter to the ground screw.
5) Close up dash and clean up. That is all.

Note- the switch and LED in the photo is the GPR and LED mod described by wmriceman previously in this forum and are unrelated to the Hobbs gauge.


Question: Installing to the PTO circuit causes the Hobbs meter to count time when the key is on, not just when the motor is running. How would a clever and wise Ford mechanic have wired this so that the Hobbs Meter is only running when the engine is running? Thanks.

 

You could run the hot wire (or ground) through a normally open pressure switch installed in an oil pressure port or even tap into fuel pressure

 

how many times will the key be on without the engine running. i wouldnt worry about it