My resistor is partially shot, the Hi setting for the blower motor won't work (it only runs up to 3/4), and while I bought a new one at some point I can't seem to find it. Does anyone know if these are still available or what the part number is? Or, thinking outside the box, has anyone tried substituting one from a car that's more readily available? (e.g. Taurus, Explorer, SN95 Mustang, MN12, etc.) I have no idea if they're the same or different.
Hmm, I did some searching and they *appear* to be readily available, though the years are a bit weird (different years for base, LX, Sport, and TC) and some show Taurus compatibility and others show Mustang compatibility. From my research it looks like the aftermarket ones have slightly different connectors so they can fit multiple vehicles. I ordered one and will give it a try.
I have an hvac diagram but like you said, the part is pretty easy to find and swap in from other cars to.
Usually the fuse blows on the resistor pack though, the windings still remain good.
the fuse can be jumpered.
If the squirril cage is heavy with debris, that could cause a little more current draw.
The resistors are not involved when the blower switch is set to Hi.
Are you saying it runs slow in Hi or not at all?
It runs at the same speed in Hi as at 3/4. Are you saying it might be the selector switch? I have a spare or two of those...
That is not a fuse in the resistor pack. That whole resistor pack thing is a thermal limiter or thermal interrupter. It does not blow because of excessive current load. There is a 30 amp fuse in the fuse panel for that.
They use those large open coil resistors so the air moving through them can carry the heat away. If there is no air movement the resistors are supposed to get hot enough to open the thermal.
They used lots of those things in main frame computers to shut the system down if not enough cooling air is coming througn the electronic circuits.
Why they use it in a car blower motor circuit, I have no clue.
The switch is not getting out of 3/4 or..
The motor can't go any faster for some reason or..
The motor is going full speed with the switch in 3/4 because there is a short between 3/4 and Hi in the switch or..one of the resistors is shorted out.
This may help:
my calling it a fuse is not correct but for general shop talk, its about the only way i can explain a thermal limiter without additional questions on what it is. Either way, when it blows, you get no power to circuits downstream.,,kinda like a fuse.
Guess a penny or tin foil doesn't qualify as a thermal limiter either(but they can make a Hellva fuse)....:rollin:
I substituted my thermal limiter with a piece of 26awg sol.
From the 84 shop manual:
The thermal limiter is located a predetermined distance from the resistor coils and opens(blows) at 121*C (250*F).
Radio Shack web site has a 128*C thermal protector fuse for $1.69.
Maybe that's the better way to go.