Hello,
Short answer to the GPC - TSU. These parts screw into the water crossover, right side. It is the big bullet part with connector and 5 wires. In the beginning the GPC was the term of the sensor.
Basically it was a thermostatic electric switch that determined engine temperature. The signal was sent to the "BOX" up in the drivers foot well. There, simple transistor / integrated circuit logic timed and solenoids applied power to energize the glow plugs. GPC was the term used throughout all of the training manuals, drawings and it sorta stuck. That was 40 years ago more or less.
"TSU" came along when the automotive electrical world decided to design controls with micro-computers in vehicles. TSU with "chips" in it, worked with those matching BOXES, the computer, supporting input/output circuitry. Say the word computer and out pops the programmers. Proprietary software ran the starting and glowing. Between the various manufacturer designing it seemed to be no standard IMO. Has a computer ??? got to have a port. (anyone ever plug in?) so add and extra connector.
While on the surface the "BOXES & TSU" all look the same on the outside. Mix and matching can raised problems. Internal working was to a large point NO USABLE SERVICEABLE goodies inside.
"Just R&R. Military talk for toss it. Remove and replace as needed the military way" I get that, who as time to mess with a computer in a war machine.
During the
hay day of HMMWV's with a couple of BOX suppliers... sometime call "SMART" with the confusion above, the sale of hundreds if not thousands to this day, with government contracts, law suites and big money was the game. (remember $400 dollars hammers) Somewhere there is a matrix as to what works with what.....
Jump ahead to the surplus market and being hobbyist, the learning curve was restarted (pun) most of the time. That's the IMO & what I've read short story.
I wonder who had the Glow Plug contract, CAMO
A peek inside>>>>
2 toasted FET glow plug output. ************ burned, welded control relay, check the affected heat signature on the armature. unit has 5 of then from you guessed it
micro-computer guess how many parts are in that
Worst case haha case prestolite GPC unit old school real old Yes, it was hanging in a truck. customer states " it ran good during the parade"
