Burning Main Fuses

[MrMarty51]

My 2000 GMT400 K3500. CC SRW Long box.
Things added that might draw some extra amperage.
Air Dog lift pump.
Electro Viscous radiator fan system.
Thats about all that I think thats been installed. No extra stereo amps or some such as that kinds of items.
First time it happened was when I realized that the PO had installed one fifty amp thats the furthest to the back in the under the hood fuse/relay box.
Installed 30 amp units whats called for in the owners manual.
Things going along just fine until I was on my way home from Missoula, round trip.
That was real early morning, had heater fan turned on, probably high as it was early to mid winter. Seemingly for no reason, lights out, engine quit running, dead, everything is dead.
Get out, that one main fuse is burned out. 30 amper unit back into the slot.
All has been well with it until last Saturday.
Wifey has the truck, she has been out for about an hour, driving around after fueling the truck.
I get the call, she is on the trail headed into my sisters place and fuse burns.
She calls, drive to location, another 30 amp fuse.
I tell her to not run the AC.
Truck is parked in front of bay door. I move the truck.
AC button still depressed, blower in off position.
One thing I have heard is the blower motor makes a kind of a quiet whirring noise.
Now I’m wondering that since we are celebrating the 250th year of the founding of Our country, if, it would be okay to liad the parts cannon with one new blower motor and take a shot at the truck with one blower motor ? ? ? ?

 

[MrMarty51]

And as a side note, the heater and AC I think has not been ran since the trip coming home from Missoula.

 

[Twisted Steel Performance]

Check grounds yet?

 

[MrMarty51]

Check grounds yet?

Yup, grounds all bright, shiny and treated with anti corrosion greasy stuff made by truck-Lite or maybe it is Truk-Lite.
I’ll go look.

 

[MrMarty51]

 

[ak diesel driver]

That is simply dielectric grease. Shouldn't be used on the actual connection just used to coat it to prevent water from getting in. In other words make the connection and then apply it on the outside to seal it. Dielectric grease is nonconductive and can interfere with the actual connection

 

[MrMarty51]

That is simply dielectric grease. Shouldn't be used on the actual connection just used to coat it to prevent water from getting in. In other words make the connection and then apply it on the outside to seal it. Dielectric grease is nonconductive and can interfere with the actual connection

Guess I’ll use that no more. Maybe on bulb bases or some such.

 

[MrMarty51]

Main grounds checked and cleaned. They are bright and shiny, including the ground strap to the firewall, RH side.
Blower motor off, engine running.
Fuse temp running 94*f.
Blower motor on high, engine running, blower motor running for about ten minutes.
Fuse temp 165*F.
IDK how accurate my IR temp gun is any more so not sure those are accurate readings.
That main fuse, WO blower motor running is okay to the touch, not cool but near normal skin temp.
After the motor has been running for a while, ten or fifteen minutes, that fuse feels as if it could near burn flesh.
Pulled the jockey box to try and get a motor temp reading but there is this plasticated cover over tye motor.
Going to figure what it takes to get that removed, then, with it still in place, give the motor about a ten to fifteen minute run, pull that covering then get a temp reading.
Allow the motor to cool, even using some compressed air, then do a rerun and see what temp the motor and fuse runs at.
I just dont know any way to run more tests.
I might have to make up some test cables and attempt an amp draw test. Get out the multimeter book and see how to hook it all in.