The temp. sensor for the Cold Hi Idle is mounted close to the #1 glow plug on the passengers side, it's a pluggin connector and easy for it to disconnect. For the HI idle to work you have to cycle the go peddle one time to set it. For the bullet connectors that fit the GP's, they are butt connectors, one side is 16/14 AWG, the other side is 12/10 AWG, available at Azone or others in a box of 6 IIRC, no need to remove the plastic cover, it'll stand the heat, or remove the plastic and solder the 16/14 side to the wire instead of crimping them on.
Check your glow plug's for resistance with a VOM meter, good ones should read about 3-6 ohms to ground. If you have on or two bad you'll get a short GP cycle, at 50* or below, the cycle should be around 10 to 15 seconds, then an On/Off cycle up to 2 minutes.
You can adjust the Cold Hi Idle solenoid, with a 1/4" wrench you can screw the plunger in or out, tom set the Idle at 950 to 1000 RPM. The Cold Idle solenoid is energized until the head temp reaches 120 degrees.
Don't be a Hardass about it, just do all of the above.