awg

So I have rehabbed the A/C on my '96 after swapping compressors/o-rings/driers from a known good one.

also swapped out the fan resistor, but found the wiring & plug on mine was toast.

The issue appears to have been caused by a corroded terminal on the resistor pack (giving high resistance, and melting one wire)

the resistor pack itself was not burnt out

which leads me to the question, of whether a relay would be a worthwhile addition, to help extend the the life of the switch?

however, from looking at the circuit diagram, it seems that the switch use +, not earth, so a single relay could only protect one "setting"..most easily max setting ?

ie, full current would be pulled thru the switch and wiring on all other settings ?

I hope that makes sense, hate trying to re-invent the wheel, so to speak

boxburn

I think you're spot on about a single relay only saving one switch contact. To protect everything you'd need 4 relays. One on each input to the resister and the bypass for full speed. It would then take the load off of the blower switch and the heat selector switch which all the current also passes through. Whether it's worth doing I'm not sure (probably). I can't say I've read that being done, however I have read multiple times about doing headlight relays which I have done myself.

dave1123

All that wiring is on the GROUND side of the fan motor! The fan is pulling too many amps and that's what's burning out your resistor. Your 96 probably doesn't have that blower motor relay because this diagram is from my 2000 XJ.

awg

Thanks for taking the trouble to post that diagram...guess it proves Jeep Electrical Engineers learned their lesson, as unfortunately, the 96 employs no relay, and +12V is switched thru the resistors

While it is possible the fan is drawing too much current, I have identified the likely culprit as a badly corroded terminal on the resistor block, causing the attached green wire to fry. (due to high resistance)

I have swapped in a resistor pack with good terminals, all good so far, the fan makes no irregular noise.

ratted a fan out of a '94, and have 2 operational ones in my '96, so if their is further issues, I will swap it to

does anyone know how many Amps they should draw, as a max?

I also noticed the resistor packs themselves gets very corroded all over, due to being in intimate proximity to moisture-filled wind

* edit..as per '96 circuit diagram I notice it draws full current right thru the ignition switch...oh the horror!..no wonder they self-immolate as well !
In this instance, I think a relay is well worthwhile to help extend the life of an ignition switch, one relay will do for the ignition issue

On an old rare vehicle I own, installed relays for ignition and fuel pump, to help protect the ignition switch, which is NLA

boxburn

Same on the 95. I think I'll at least do a relay on the feed too to help my ignition switch.

dave1123

The problem with any electrical circuit is the connectors. They all have a certain amount of resistance even when clean. Usually this is negligible, but once they get coated with oxidation or loose their tightness, resistance gets a lot higher. This resistance causes heat and increases current flow and/or voltage drop. Pretty soon, things start to melt or flash over. Once an arc forms, localized temps can get over 35,000 degrees for a high amp circuit. Metal vaporizes. Anything nearby starts to burn. Fuses don't always blow quick enough to stop things from catching fire. That's why one of my stoplight harness connectors melted without blowing the fuse.

awg

So I did this mod and hid the relays behind the side kick panel, all totally reversible

I only did the lower 3 speeds. The splice for "max" must be up behind the dash somewhere, probably direct from the switch

this is not a game ender, as I know to avoid using that speed is desirable, and speed 3 is nearly as high

its a bit of a hassle but for ~$20, my ignition switch feels much better protected..(I also have headlight relay protection)