HVAC FUSE KEEPS BLOWING

Is it the fuse to the blower?
Is it the fuse to the compressor?

 

If it works fine sitting still but blows when you are driving , I’d guess the power wire going to the blower has a short that is getting grounded when driving due to the vibration of driving .

First place I’d look is where the wire passes thru the firewall or somewhere the wire is close to some metal

You own this truck or someone else own it ?

if it’s yours ,
You could bypass the bad wire and just run a new wire from the control to the blower .

Start by unplugging the blower but turning it on at the controls

that should put power on the wires
It could be a short inside the blower motor itself .

 

Hard wire plug

 

Front Blower or Sleeper Blower ?
If you look on passenger side Behind seat half way up their is a plug under the sleeper to cab boot
Check that the wires have not got hot and melted.

 

You will need to just find the spot where the insulation has rubbed off the wire

it will most likely be where the wire passes through the firewall or something , or at or near a connector plug or at or near where the wire is attached to the body with a P clamp. Or where the wire is rubbing on something , or where something is rubbing on the wire .
it doesn’t take long for a airline or anything that vibrates to wear through the insulation on the wire .

The controller for the speed of the blower , is also an area where this could be .

I don’t know if your truck has an old fashioned controller with the resistors , or if it has the computer to control the speed .

also check the blower motor itself

unplug the blower from the harness , and go for a test drive ,
If it doesn’t blow the fuse , then it’s Probabaly the blower motor or the wiring inside .
I had one that kept getting wet and it wouldn’t operate properly
I replaced the dash controls and replaced the electronic speed controller etc
When it turned out to be the motor itself was damaged from getting wet

I stopped the water from getting into the motor and it’s been fine since .

start by unplugging the motor and do a test drive .
If it still blows the fuse then you know it’s not in the motor or the plug at the motor ,
So follow the wire harness and find the next connector plug and unplug it and go for another test drive ,
If it still blows the fuse then you know it’s not in that section of wire so follow the wire and find the next plug etc

once you narrow it down to which section of wire it is , then you can start looking for the damaged spot and repair it

if you can’t find the damaged spot but ARE able to isolate which section of wire harness it’s in, then you can bypass the damaged wire with a new wire , or replace that section of harness .
I have a vehicle that has a large connector plug thru the firewall
And that connector just doesn’t always connect the wires

I just isolated which wires don’t connect and bypassed the big connector
I moved those wires out of the main connector and made my own connections

drilled a hole on the firewall , inserted a grommet and passed the replacement wires through the grommet and used bullet or butt connectors .