Little Trucks, Big World

so today my blower fan died i think, I am getting power to both wires?? but when i ground the green one (it may be blue) it works i get nothing from the swith though. what could this be, and for the past few months I have had to give it a little bump for it to turn on every now and then. also i tested the green wire for ground and power it has neither but has power with the red one plugged in. its a 4 speed blower on an 85 720.

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It would seem that the switch may be making bad contact. Remove the switch assy and have a look at it.

i was messing with the switch and nothing happened. and before if i wiggled the red wire on the fan motor when it didnt work it would go right on, what is puzzling is why both wires to it get power when both are plugged in should it be that way? also the fan goes right on when i stick the green wire on a ground but only high speed and the switch does nothing. 

also keep in mind i am trying to recover from a bran injury from an accident i had on the 20th so im a little slow also my speech went away right after nissan fest lol perfect timing so trying to figure this out with half a brain is hard and not being able to talk right also sucks

Wow Forrest, I thought your broken arm was bad enough, didn't know you were dealing with this too...  Was it a concussion?

Hey the fan also has it's own fuse, and a relay, that could be loose or acting up.  But if that's the cause, you won't have battery voltage to the motor at all.  The heater relay is the second from the left above the fuse box.

You should have ground going to one wire on the switch, the other three wires will vary depending on what position the switch is in (and if the motor is hooked up or running).  In the off position, you'll have battery voltage on all the other three wires.  If the switch is on low, these voltages will be lower, or nearer to ground.  The switch is changing the value of a current limiting resistor (the heater wire resistor) on the negative side of the motor.  So, the motor + will always have battery voltage on it when the relay is on.  The - side of the motor will be ground, or very near to it, depending on the position of the switch.  On high position, you should have ground on the - side of the motor.  If the motor itself is bad, you can have battery on the + side, and ground on the - side, and it still won't run.  In that case, it's either stalled, or the brushes are worn out and not making contact.  If it's stalled, you'll probably blow the fuse.

If wiggling the wire affected things before, it's probably part of the problem now.  Either a loose connection inside the fan unit, or the wire leading in to it is broken internally, or where ever that wire is coming from (which should be the relay) isn't making good contact.

Since you get high speed when you ground the green (blue) wire, in high, the resistor is bypassed by the switch routing the - side of the motor straight to ground.  So, either a wire between the motor, resistor and switch is bad, your switch is bad, or you have no ground going to the switch...  You should have ground on the black wire going to the switch.  And in the high position, you'll also have ground on the blue wire...

Well luckily my arm was not bad enough for a cast but this head thing sucks. I'm going to have another look at the switch and see what I come up with. I took the motor apart and all seems fine so I think its a ground somewhere, where would the ground be because the green wire is dead no ground or power

First check that you have ground on the black wire of the switch, if you don't have it there just run a ground wire to it temporarily and see if everything works then.  If you have ground at the black wire, then put the switch in high position and make sure you have ground at the switch on the blue wire.  If you don't, then the switch or the is bad.  If you do have ground coming from the switch on blue wire in high, then most likely the blue wire is bad between the switch and the motor.

I don't recall exactly where the ground wire comes from to the switch, but worst case you can just ground it to the metal frame of the dash, it should be a fairly good ground.  But I believe the ground is near the fuse block, or under the instrument cluster.

Sometimes on my blower,it won't come on and /or it will come on then go off,the fuse in the fuse box comes out a little,I just push it in and it works,only does it maybe twice a year. 





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