have an '88 Fsuper duty... 7.3 IDI, 5 sp. non air.. glow plug timer started short cycling... replaced plugs, timer and harness... did the same thing.. head lamps started to go dim... alt. at 14.2 volts... new batteries. all grounds good... started to smell heated electrical insulation.. pulled dash... found melty goodness in head lamp switch and fuse panel...my question... are all basic under dash wiring harness' the same or, are they specific to gas v diesel, a/c v non ac etc..I am thinking that my harness is toast... have to replace it... need to know what will work... also, are there any other places to look for the root cause of electrical woes.. this is a new truck for me... too hi tech... all my other rides were much simpler... biggest problem was pulling points and installing petronix... thanks in adv for any input...

 

the headlight switch and harness are known to heat up and melt.both are easy to replace.
what did you find exactly for melted wires at the fuse panel?

 

Too high tech? It doesn't get any simpler than a MT IDI truck. Like HDXLT said, it is common for the headlight switch and connector to overheat and melt. New connectors should be available at any parts store. They come with 6" or so of wire and you splice into your old wiring. A headlight relay kit will reduce the current going through the switch so it won't happen again.

 

head light plug has been replaced... hi/lo beam floor mount pigtail and switch also. headlight switch is a NOS D3TZ for an F700.. where should I install the head lamp relay?... there is a relay on the drivers side inner fender for tail/body lamps to rear... still has a rapid relay clicking for the glow plugs... dash instruments react with the relay clicking... as do the fuel gauges.. in the event I start to dissect the wiring harness and find too much to replace... what harness is compatible...are there any other problem points to look at... plug through fire wall. harness for other accessories?.. thanks again for the help