I have a 95 YJ, heater only, 2.5L. Bought it used with this problem, so no background, other than it worked for years and then one day, the heater no longer worked. I've done some research and did what I could, but as far as t/s electrical circuits in cars, I'm not the greatest.
Onto the problem:
1. The heater fuse (25A) on the driverside keeps blowing when I turn the ignition to on.
2. There is battery power applied (12.5) to the left side of the fuse when looking at the fuse block, only when the ignition switch is on, or otherwise the fuse is fine and no power present.
3. I've verified that the heater motor works with an external battery.
4. Everything is unplugged and still blowing fuses (heater controls, resistor, and motor).
5. Tried to Ohm to ground all wires, and nothing happens (good right).
Now I'm at a bit of a loss. Any ideas or insights?
im having the same isues with mine. but mine is melting the fuse. i did check the prongs in the fuse box and found a little piece of a fuse that must have been from previous fuses that keeps sparking (from getting power and then vibrating loose again) May want to take a good look and make sure the prongs are clean
Check wires going to your heater fan or switch panel. Sounds like it is grounding out. Most common electrical shortages is from power wire touching ground. It could have a small tear in sheilding or got pinched between something. Find them and try to trace them to power source.
This is starting to sound like an on going problem,been running with no heat for a week. until I can get my jeep back in the shop to tear it apart to find the cause .mines melting also. Also on the hunt for another harness .my fuse block is pretty badly melted,or after I find the problem Ill just tap in a single fuse holder.
Ok, I know this would be a bandaid fix, but theoretically, If I ran another hot wire and of course fused it, and found the main hot wire to the switch, I could essentially bypass the heater fuse and possibly still have heat, with everything connected back up? I suspect I have some issues with the ignition switch to the fuse.
easiest thing to do is to disconnect connector going to blower motor ( motor may have a short ) if it still blowing fuse then U have to check the wires going to blower motor
LMK if u need a wiring diagram GL
Even thought you have tested that motor with a battery it may work. It may be drawing more amps then the circuit was designed for. I assume u did not use a fused circuit when u tested it with another battery?
Gentlemen: I have the same issue(JeepSurfer)...95 Rio Grande...keeps blowing heater fuses only when the ignition is turned on. I have tore the dash apart and disconnected all electrical heater connections on the switch & assembly, the resistor at the blower motor...everything. I thought that would find the problem. Put a new fuse in it...switched on the ignition...it blew the fuse. That eliminated everything from the switch to the blower motor. I am still looking for the problem. My next step is checking the loads and continuity on the fuse panel. I hope to do that today. I'll post my finding when I fugure it out.
Here's something interesting...with the cables off the battery I show continuity on the right side of the fuse panel. I aslo show continuity on the positive side of the battery cable to ground on the chasis. I'm not quite sure yet where to go with that.
You will still read continuity because the power wire is connected to everything electrical on the vehicle. As long as you have a short somewhere then you will read the power wire to ground with continuity.
You will need to isolate the heater circuit from the battery circuit onestep at a time from the heater switch>fuse box>fusable links>battery.
Check the back of your fuse box for corrosion from the years of moisture getting to the wiring everywhere on the jeep. Sometimes the electrical grease gets removed from areas on the fuse box connections and allows rust to set in.
In the summer I noticed my blower wasn't working, took it to the shop and they said it was a blown fuse, free of charge to replace. On the way home it blew out again. They wound up finding a short in the actual heater switch assembly in the dash(and it was fried), it's a $400 part but found a used one for $200. Put that in, worked fine from October til now. I was driving to test out my new headlights and this huge spark came flying out from the fuse box toward my left foot. I was only around the corner from my house so when I got home I knew it was the heater fuse and sure enough I reach up and it was really hot, pulled it out and it was blown.