coolent temp sensor and the ailments of my eletric fan?

Ok so, I have a 90 xj and useing a lazer temp gun, I follow the temp of the thremostat houseing, and the coolent sensor on the rear of the head. I have come to undersstand that at 220 the secondary fan is suppose to come on. It doesnt come on till about 245 or so. I have come to understand that the sensor on the back is incharge o turning this on, and that there is a ground strap to clean the connecton for.

so with that being said i have two questions.

Where is the ground strap I simply cannot find it.

Should I do both clean t he ground point, and replace the sensor?


Thank you so much in advance for any help

peace
ted

The one on the head runs the gauge. The sensor in the lower driver's side of the radiator runs the fan relay. Braided ground strap goes from driver's rear head bolt to firewall just below the cowl. Main engine grounds are under engine oil dipstick tube bracket on passenger side of block.

Agree. Dipstick tube grounds are ICM, ECU, and o2 sensor. Main battery ground is to engine block. Main body ground is the braided strap at the rear of the head to the firewall, driver's side. I like to replace the braided strap with short cable, the straps deteriorate rather quickly. Adding an extra battery to ground at the fender well on the passenger's side is a good idea.