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Uncommon blower motor/hvac controls not getting power
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.
Uncommon blower motor/hvac controls not getting power
Okay so I have a 96 xj 5 speed 4.0 motor and I've had problems with the blower motor switch before it was really ****in melted when I took it out. . That was About a year ago.. And changing the switch fixed it until now I'm having an issue where all of the heater units controls don't seem to do anything I've checked all of the fuses in the under dash panel every fuse down there checks out and under the hood so far I've changed the fan control switch and the motor resistor itself (noted when I pulled the resistor out there was alot of leaves and a furball that came out of there?!) also I've checked for power with my test light all over there's power at the harness that goes into the passenger side of the hvac control unit but no power on any of the leads to the switch, resistor leads, or the blower motor itself harness??
Last edited by Jeepman659; 02-20-2019 at 12:02 PM.
Now after doing the blower motor test I turned on the headlights out of curiosity now the ****ING illumination for the dash light/4wd light all flickered and now aren't working.. Needless to say I'm getting real fed up here..
Last edited by Jeepman659; 02-20-2019 at 12:13 PM.
the only place I can find power in here I took a video to show that the cable isn't moving behind everything? The controls move and feel the same they did before when it was working?
If anyone's even reading this I really could use some advice here.. Is it a good idea in this situation to run a power wire from the fuse panel to the switch directly? And why do you guys think my dash lights stopped working all of a sudden?
I managed to get everything working the dash lights and the blower turns on now it was all just a bad connection where I spliced it before it seems because I re crimped them and everything's fine other than now the top slider only turns everything on half way between off and max A/C ?
I'm new to the forum and still getting used to looking for things. I noticed in your picture that the brown connector (original) looks like its missing, it plugs into the 5 pin switch. Mine is melted so no fan at all. That part is not available so what did you do to connect together. 5 pin brown relay
I'm new to the forum and still getting used to looking for things. I noticed in your picture that the brown connector (original) looks like its missing, it plugs into the 5 pin switch. Mine is melted so no fan at all. That part is not available so what did you do to connect together. 5 pin brown relay
OK..I took the 4 screws and commenced removing the heater controls yesterday
Reason;...that POS design needs a relay inserted to prevent FULL fan current traversing the Ignition Switch..lucky it isnt toast instead!
to fix your immediate situation each wire needs to be terminated seperately with an appropriate spade, insulated with heatshrink, and plugged back in.
(or run wires from battery)
I have not got so far as even determining where I am going to insert the relay in the circuit, but will run a new wire straight from the battery
Want to retain all 4 speeds, so have to figure that out from the circuit diagram
I purchased a new black switch so maybe that has the relay in it and the brown melted connector just plugs into it. The pins are labeled on the black switch. Thank you for responding so quick. I found a 3 pin and a 2 pin connector so I'm going to use those to plug into the switch, that way they are insulated better.
Originally Posted by awg
OK..I took the 4 screws and commenced removing the heater controls Hester Ray
Reason;...that POS design needs a relay inserted to prevent FULL fan current traversing the Ignition Switch..lucky it isnt toast instead!
to fix your immediate situation each wire needs to be terminated seperately with an appropriate spade, insulated with heatshrink, and plugged back in.
(or run wires from battery)
I have not got so far as even determining where I am going to insert the relay in the circuit, but will run a new wire straight from the battery
Want to retain all 4 speeds, so have to figure that out from the circuit diagram
I purchased a new black switch so maybe that has the relay in it and the brown melted connector just plugs into it. The pins are labeled on the black switch. Thank you for responding so quick. I found a 3 pin and a 2 pin connector so I'm going to use those to plug into the switch, that way they are insulated better.
update..the blower switch and harness to the blower resistors carry all the current...this is a very bad design, corrected on the post '96 models
this means imo there is only one way to fully overcome the issue, which is to place a bank of 4 relays adjacent to the resistor pack, run battery power to them,
1 relay for each speed, all "behind dash" parts carries only enough current to trigger the relays
I stand to be corrected on this matter by other posters with electrical knowledge of pre '97 ? (anyone can have a go lol)
cost of 4pack of relays ~$15
ps..check for any corrosion of connectors at resistor pack, this causes resistance, high current & heat
update..the blower switch and harness to the blower resistors carry all the current...this is a very bad design, corrected on the post '96 models
this means imo there is only one way to fully overcome the issue, which is to place a bank of 4 relays adjacent to the resistor pack, run battery power to them,
1 relay for each speed, all "behind dash" parts carries only enough current to trigger the relays
I stand to be corrected on this matter by other posters with electrical knowledge of pre '97 ? (anyone can have a go lol)
cost of 4pack of relays ~$15
ps..check for any corrosion of connectors at resistor pack, this causes resistance, high current & heat
Yes, you are correct. 96 and older have Ignition switch and fan speed switch carrying the full amperage/current for the HVAC blower motor. It is particularly bad at full fan speed, where the fan motor can draw approximately 20 amps. Luckily, I got to mine before the ignition switch fully melted down. If someone doesn't want to do a full relay conversion, one very good habit to develop is to run the fan on max only for short periods of time and then switch down at least one speed. That cuts the amperage nearly in half (from 19 down to about 10 amps - depending on age and condition of the fan motor). Cutting a breather hole in the steering wheel shroud can also help keep the ignition switch connector a bit cooler and give better opportunity for periodic visual inspections.
I'm surprised they got away with the design, because the wire gauge, and connector types definitely don't seem to be sufficient for that type of amperage for extended periods of time. Its a cabin fire waiting to happen. Also, at 20 amps I think that puts the fan motor as the 2nd highest amperage component in the vehicle, only behind the starter.
Last edited by jordan96xj; 05-31-2019 at 09:33 PM.
On 87 to 90 MJs and XJs, the blower motor’s factory grounding point is on the driver side inner fender under the sheet metal screw. This ground is shared with windshield wipers, front windshield washers, rear windshield washers, AC clutch relay, fan control relay, fog lamps, fan motor, headlamps, front turn signals, front side markers, and park lamps.
So your blower motor has its ground point 10 feet away from where it is located!!
What we’re going to do is leave that ground intact and also ground the blower motor on the passenger side inner fender much closer to the blower motor itself. This will also benefit the other components on the factory ground circuit. Take this opportunity to refresh the factory ground as a matter of course. Remove the screw, scrape the surface to bare metal and reinstall the screw securely.
Here’s what I do to get the ground much closer to the blower motor and add another ground point to this overloaded ground circuit.
Find the blower motor connector on the passenger side. Red and Black two wire connector.
Find a location where the black wire can be made to reach the passenger side inner fender, and cut the wire. You may have to do some rerouting of the harness to achieve this.
Take both cut pieces of wire and put them together into a yellow eyelet and crimp. Fasten the eyelet to a place on the passenger side inner fender with a sheet metal screw after applying OxGard to the contact surfaces. Be sure to scrape the attaching point on the fender to bare metal first.
Your blower motor will now turn faster and last longer, and the other electrical components on the circuit will benefit from a better ground path.
I found another brown 5 hole connector. The person said its missing the ac wire because he didn't have ac. I have ac but my old connector doesn't have that wire either, not sure why. I get it all spliced in and yay, I have fan speeds. I take it for a test drive, shut it off four a bit, start it back up, no fan. Leave it on and hit a bump and fan comes on. Do you think I should look for the ground wire? The black heater blower switch that this plugs into has a B, M, AC, then second row has L, H. I will be buying a repair manual and hopefully get a wiring diagram. Any suggestions appreciated. Thank you, Karen
02-20-2019, 09:05 AM
Uncommon blower motor/hvac controls not getting power
