Need schematic for A/C switch

[jramirez35]

Just bought a 1990 Bronco XLT w/N code 5.0L engine. Love the thing except for the oil leaks and minor little things that need some TLC. First norther blows in in next couple of days and need heater. Dude i bought this off of removed the a/c blower motor control switch and direct wired (i think). I can get this switch at oreilly's or autozone which was actually a shocker, but i can't get the male end of the socket for the back of this switch nor do i know what the wiring scheme is for this. I see four blades on the back of the switch socket and will just put some terminals on it and mate them to the switch directly but the haynes manual i have for this does not have this wiring diagram. Also, when i turn on the a/c it causes the voltmeter to go below the "middle mark" and makes it look like the charging system is not operational. With the a/c off, the voltmeter is showing a good indication. Could bypassing a switch actually cause the charging system to fail or is it just loading it down for some reason? Any assistance with this would be greatly appreciated.

 

[jramirez35]

I'll hookup with the autoparts store and see what they say. I was more curious as to why this would happen and if it made any sense to anyone else. I figured that by hardwiring the blower motor that you were bypassing the resistor or some other kind of regulating circuit and that was causing it but i have no way to prove that and was trying to diagnose it. Also forgot to mention that the control will be on high a/c with blower motor hardwired and it will blow "cool" air out of the vents and then it will just switch to the defrost and blow it out of the defrost vents. Any ideas? thanks for the quick response.

 

[skrap420]

where is the resistor located exactly? my truck had the same problem only the previous owner did something to cause the connecter that plugs into the fan speed switch to melt into a ball of molten plastic and wires. so im trying to find out why he did this and also am trying to figure out how to remedy the problem.

 

[jramirez35]

I took pics of my vehicle and will upload them soon because i had questions on the tags from the xfer case, front diff, and rear diff. already figured out the tranny.

 

[jramirez35]

Ut works like a champ. Blowing real cold so i think the thermostat is not installed. Fan is blowing very hard now out the front vents...exactly the fix that this needed. I am sure the dude that i got this from didn't know about this fix and he went about every other thing but a vacuum hose. I attached a pic of what the hose looked like. White just like you said it would be and pretty ate up as well. I will try to use the old switch that was in the back of the Bronco and see if i can figure it out. It is only four wires and 1 has to be 12V and the others go to the blower motor resistor so we will see. Thanks for your help. I have pics of tags off the diffs and xfer case but i don't think i will post up because i see the pinned posts regarding how to read this. Maybe ask later if i can't figure it out...God I love this truck!

 

[jramirez35]

fan is still only blowing on high setting but i was able to trace everything back and had a pseudo-schematic to work with from autozone.com, which actually freaked me out. It is only off by one pin on the switch (they have 5 and i have 4) but it was fairly accurate with the right wiring colors and everything. I will replace resistor next because it sounds like for the most part in all other settings it is at a high resistance and not passing voltage to the motor. in highest fan setting it is switched ground directly to motor...all other settings just don't seem to work. I hope that is all and i can then move on to the next malfunction. I also put a multimeter across the battery posts when the fan is on and i show 13.2V and 14.0 with the fan off so that looks good. Any other suggestions would be appreciated.