Howdy
A few other things to check:
Switch issues in the dash, I cant remember how that model switches but I know in the newer trucks they ran high current through the switch and they had a tendency to burn up.
Resistor pack for fan speed control. This is mounted in the air box and can also cause problems.
Relay pack mounted on top of the air box
Some trucks had a connector for the high speed circuit in the fan wire and it could overheat and become a problem as well.
The high speed circuit is separate from the others and it sounds like yours is heat related due to the current draw.
good luck!
1996 Chvy 3500 CCDWLB 6.5 Heathed, NO vac, marine injctrs, ARB bumper, BIG pipe, 3" lift, bright lights, bypass oil system.
1986 Chvy 6.2 M1009 blazer RAM AIR, Headers, Custom interior
2001 Chinook RV, V10 gas
1974 John Deere 1530 diesel tractor
1993 John Deere 455 Diesel lawn mower
1967 GTO, 1989 Honda Transalp
2009 VW Jetta TDI, flashed and piped, 6speed, fun car!
1998 6.5 suburban, stock, daughter's
1993 6.5 3500 CCSWLB GM8, Heathed, big exhaust, gauges, Son's
1984 6.2 ATS turbo 3500, SCDWLB - Son's
3 kids, 1 wife, 1 dog
Gunsmith, Tactics Instructor, Fabricator USMC 87-93 Semper Fi!