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a quick electrical question

Devil_Mutt

Devil_Mutt

NAXJA Member #1244
Location
Mississippi
A while back (last winter) the resistor pack on the HVAC controls got so hot, it melted the plastic and cause a small fire. Word of advice... try to avoid the knee jerk reaction and slap it out with your hand. Melted plastic doesnt tickle. Anyway, cooler weather is approaching, and Im looking for a temporary fix for now, so what I have decided to try and do is run my blower fan directly off of a hot lead thru a relay and a toggle swith. I realize this will only run wide open, but Im okay with that. My question is... is there any particular type of relay or size I should look for? Im not very familiar with relays, so any help or advice is appreciated.
 
I just spliced into the hot wire from the plug & then back to the wire for the high position. Through a toggle,of course. This way I have low & high. This way it runs through the factory relay( I think ). It's worked for 2+ yrs. JIM.
 
Wouldn't be surprised by around 30 or possibly even more, check the fuse it runs off? That'll give you a max value. I know the wiring going to it is either 12 or 10 gauge which implies 20 or 30 amps range, and the blower motor speed resistor is pretty heavy too.
 
Devil_Mutt said:
anyone have any idea how many amps the blower motor pulls?
Click to expand...

Stop at a parts store and ask them to let you look at a blower motor for your year XJ--should have amps on the housing.

I haven't read of anyone suggesting a different resistor pack, something a little heavier? I don't believe there is any factory relay in the switch/resistor pack/blower motor circuit, but judging by the number of problems there should be one for the resistor pack/blower motor to take the load off the switch and dash wiring.

I guess you would have set it up with a "bank" of relays for the various speeds.
 
I'll look at my XJ manual when I get home tonight.

When I worked for Buick there was a relay in the circuit. I am quite sure the XJ is not much different. The GM fan is designed to run all out all the time and the dash switch just selects which path through the resistor pack. The rsistor pack then reduces volts to motor and that reduces the speed.

The blower motor amp draw will be less than the fuse for that circuit, so either < 25a or 30a.

I have an 89 manual but it should be the same so it can indicated what color wires serve which purpose..
 
Be sure and check the plug at the ignition switch. The brown wire (I think) has a tendency to cook and melt, when the resistor pack fails and shorts.
 
Per my 89 Manual.
Fuse #12 is for the blower. It is a white 25Amp.

Wires in circuit are all 12 ga. I was incorrect, there is not a blower motor relay. If you place an on/off switch in circuit in line between the 12g Light Blue wire (resistor input) and 12g Orange w/black stripe (resistor output) you effectively by-pass the dash mounted fan switch and the resistor block. You should still have the always on lo and then when the by-pass switch is energized closing the circuit you'll have high speed fan operation.
 
Boatwrench said:
Per my 89 Manual.
Fuse #12 is for the blower. It is a white 25Amp.

Wires in circuit are all 12 ga. I was incorrect, there is not a blower motor relay. If you place an on/off switch in circuit in line between the 12g Light Blue wire (resistor input) and 12g Orange w/black stripe (resistor output) you effectively by-pass the dash mounted fan switch and the resistor block. You should still have the always on lo and then when the by-pass switch is energized closing the circuit you'll have high speed fan operation.
Click to expand...

That's what I did. Not sure on the wiring colors, mine's a 96, but the same concept. JIM.
 
Devil_Mutt said:
So, what would make the resistor pack heat up so much that it melted the plastic around it? Excessive amp draw from the motor?
Click to expand...

Essentially the wires are all too small, and they should have been put on a relay to begin with. Stupid to run that much current through a switch.
 
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