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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
When I first put my XJ together the A/C wouldn't work. Couldn't get compressor to come but had too much on my plate so dealt with it for 2 summers. Last April I decided enough is enough. After spending some time diagnosing electrical I came down to there was no vacuum at the mode selector. Furthermore, the leak was under the dash.
So I went through this
To find this
I contact cemented it together and wrapped it with gorilla tape. That sucker is never coming apart. Put it all together and viola had A/C and life was good. Well until the fall.
Went on a wheelin trip in the white mountains which got kinda cold which was first time I needed heat. Worked fine but when I got home didn't much need heat again until I went to Anthracite mid November with snow and quite cold. I picked a bad line on an obstacle and got hung up. I was getting ready to pull line when my wife said she smelled smoke and I did as well. Then I noticed blower motor wasn't running. Checked controls and yup blower was out. Said frigg it and went on wheelin.
I have a pickup I drive most of the time and used the Jeep when it was mild out. Last weekend my New Years resolution was to fix the heat. Ruled out the blower motor and resistor so got into the dash expecting to find the switch burned out but no. Now all these parts were put in new 3 years ago. Then I find I have now power at all on any of the lines to the switch. Checked the fuse which I guess should've been step 1 and yup that's good and fuse not blown but I changed it anyway because I get paranoid like that. Nada. I checked the wire up the steering column but don't see any melt.
Next thing to check will be the ignition switch but the only problem is heat. Wipers and turn signals are fine. I decided to give it break last night because I was getting visions of tearing the dash back down to the firewall again.
Everything AFTER the blower motor feed is a ground circuit. This may help even though it's the circuit for my 2000 XJ.
Thanks but this appeared to be later model. I have the one for 94 and after tracing it down further I found this:
I was focused on the blower switch which is typically the issue but the second from the right is the power feed from the mode selector to the blower switch. The plug on the mode selector was in worse condition.
Hard to see but it was melting through the bottom. I have a replacement for the mode selector switch but the plug is a problem for me. I have no pick n pulls by me and don't have a donor. The design doesn't allow for just crimping on spades like you can with the blower switch.
If someone has a donor or can source one for me please let me know.
Make sure you put a new blower motor in it as well. Melted blower motor parts means the worn out motor is drawing too much power for the wiring to handle.
Make sure you put a new blower motor in it as well. Melted blower motor parts means the worn out motor is drawing too much power for the wiring to handle.
Blower motor is new. So is the resistor and blower switch. Not sure why this plug melted like it did. Best I can guess is contamination and gook that got in there and caused a short. I broke the switch apart to see what was inside and the heat was all inside the plug and on that tab of the switch. Nothing inside the switch or down the wire behind the plug. Damned odd.
Again if anybody could help me source a plug from a donor I'd much appreciate it.
The higher the amperage draw, the less any resistance can be tolerated without causing significant heat. The blower fan can draw between 9 - 20 amps depending on the speed selection and age/condition (It is probably the 2nd highest amperage draw on the vehicle next to the starter). So it's a relatively high amperage item, so a little resistance in one of the connections can cause a problem pretty easily - and quickly. In 96 and older XJs, the fan also draws amperage right through the ignition switch and connector, so it can not only take out the HVAC, but also disable the vehicle. This also causes a fairly serious fire hazard within the cabin, and that is why in 97 they finally moved away from loaded circuits in the cabin, and went to the more modern approach of most cabin controls working through relays.
For those that own 96 and older. I highly recommend that you inspect your ignition switch next time you can. Inspect the condition of the wires for browning/scorching. I would also recommend -NOT- running your fan on high all the time. Instead use it on high at first, but once you are warm/cold (whichever) turn it down one notch. That will significantly reduce the amperage draw (almost cut it in half).
The higher the amperage draw, the less any resistance can be tolerated without causing significant heat. The blower fan can draw between 9 - 20 amps depending on the speed selection and age/condition (It is probably the 2nd highest amperage draw on the vehicle next to the starter). So it's a relatively high amperage item, so a little resistance in one of the connections can cause a problem pretty easily - and quickly. In 96 and older XJs, the fan also draws amperage right through the ignition switch and connector, so it can not only take out the HVAC, but also disable the vehicle. This also causes a fairly serious fire hazard within the cabin, and that is why in 97 they finally moved away from loaded circuits in the cabin, and went to the more modern approach of most cabin controls working through relays.
For those that own 96 and older. I highly recommend that you inspect your ignition switch next time you can. Inspect the condition of the wires for browning/scorching. I would also recommend -NOT- running your fan on high all the time. Instead use it on high at first, but once you are warm/cold (whichever) turn it down one notch. That will significantly reduce the amperage draw (almost cut it in half).
For those that own 96 and older. I highly recommend that you inspect your ignition switch next time you can. Inspect the condition of the wires for browning/scorching. I would also recommend -NOT- running your fan on high all the time. Instead use it on high at first, but once you are warm/cold (whichever) turn it down one notch. That will significantly reduce the amperage draw (almost cut it in half).
good advice there!
Question, would a relay in the spot (marked in red), placed in the engine bay adjacent to fan, save not only the Ignition, but all other inline items?
run a wire from battery, and intersect the main wire to fan in engine bay, which I think is dark green in a '96
Question, would a relay in the spot (marked in red), placed in the engine bay adjacent to fan, save not only the Ignition, but all other inline items?
run a wire from battery, and intersect the main wire to fan in engine bay, which I think is dark green in a '96
Yes but only if the fan were to operate at all or nothing. A relay after the heater selector switch would save the ignition switch and heat selector switch from the load but the fan switch would still bear the grunt. 4 relays, one after the fan switch and before the resistor pack would be required to save everything from the fan circuits load.
Thanks for following that up boxburn. I'm getting better at 12v electronics, but I really don't have the experience yet to analyze a circuit for someone and be accurate in my advice.
What you mentioned is pretty much the reason why I have not done this mod, because I have seen posts about it before and it creates such a mess of new wires and relays that in the end I just didn't think it was worth it. Instead, I am just more aware of how/when I run my fan and how long I let it run on high. I also feel the bottom of the steering wheel trim to keep an eye on how hot it is getting inside there. I also intend to drill an inspection port in the bottom of that trim so that I can occasionally inspect the connector and wires without having to pull the trim/shroud apart. Luckily, I initially found mine getting hot before it did too much damage, so I was able to clean everything up and re-insulate things and better protect the area from shorts (the ignition switch connector runs right under the machined steering column metal which is grounded, so if the insulation on the wires fails (gets burned) that amperage wants to jump right to the steering column. Since then I have tried to boost awareness on here, particularly among those with 96 and older.
Yes but only if the fan were to operate at all or nothing. A relay after the heater selector switch would save the ignition switch and heat selector switch from the load but the fan switch would still bear the grunt. 4 relays, one after the fan switch and before the resistor pack would be required to save everything from the fan circuits load.
right you are, and my bad, I should have known better...one of the good things about a forum, it can save you from yourself
pretty paranoid about ignition switches..one of my '96 has a nightmare aftermarket switch fitted..God only knows why they went that way
Clearly, with A/C and headlights, stereo blaring, one is asking for trouble really
Might have to start with just one relay for max setting, do the headlight harness relay thing too.
Some guys fit a wrecker XJ (or other) PDC in the engine bay, with the relays and fuses
01-02-2019, 11:29 AM
The struggle continues
