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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.
The factory manual and wiring do not give values. And, you shouldn't be concerned with the exact resistance as whether or not the resister bank is open or closed.
NOVEMBER 28, 2015CRUISER5428 COMMENTSOn 1984 to 1990 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.
Na cruiser your all good. Ill do that also. And the readings are all the same on the resistor with in like .60 ohms of each other but stuck on low speed.
Check your voltages on the other leads when your blower switch is set to anything other than low. Voltage is fed at the resistor bank at different points (at reduced total resistance) to increase total voltage. Except for HIGH… that comes off the blower relay. If I remember correctly, pin one always has voltage and the blower is on. Pins two and three will have voltage only one selected for the next two blower speeds between the lowest and highest selection.
I've looked in several fsm's and none list any resistances. The resistors essentially are linked in series with a junction between each one. So when set to low speed, the path to the fan goes through all of them. When set to a medium speed, the flow bypasses one or two on them (depending on the setting). In high, the resistors are bypassed completely. That's why one only gets the high speed if the resistor is blown.
What exactly is the problem? Stuck on low speed only?
Here's the diagram. The LT BLU is the feed from the AC Mode select.
I was just about to ask if we can post a picture of the diagram... you beat me to it. Now he can see what I was trying to describe.
The terminal marked "3" always has 12 volts when the HVAC is set to on. If the **** is set to anything other than low or high, voltage is re-directed to terminals "2" or "1" to bypass some of the resistance, thereby reducing voltage drop to the motor. If any of the resistance is open, the blower won't blow on the lowest setting.
So left to right i will number them 123 and top is 4
The only one found hot is 3 to 4
So 3 to 2 nothing, 3 to 1 nothing, 3 to 4 pin read settings on all settings. 3 to 4 low was 8.07, 3-4 med was 6.6 volts, high was 5.6. nothing else read besides 3-4 on any settings.
Last edited by white hawk; 01-01-2022 at 10:10 AM.
Here's a better diagram from the '90 FSM. It also shows the pinouts on the connector. On the schematic, Pin 3 is the hot "when key on". Pin 6 goes the blower motor. Your Pin 4 is Pin 6 on the diagrams.
So pin 3 is always hot. Note the other paths are all open. Since the current has to flow through all resistors, you get the slowest fan speed.
Now switch to M1. Now pin 2 is also hot but bypasses the first resistor. Since electricity seeks the least resistance, the blower spins faster due to the reduced resistance.
Now switch to M2. Now Pin 1 is hot and bypasses 2 of the resistors and the blower speeds up.
Finally switch to high. Note the direct connection to Pin 6 bypassing all of the resistors so the blower spins the fastest.
I would test for resistance across the pins of the resistor. So Key off!!! Remove the connector from the resistor pack. Measure Pins 3-6 (note resistance), then 2-6, 1-6. You should see decreasing numbers.
Then I would check for voltage at the harness connector so leave disconnected. So Key ON. AC control in any position other than off. Pin 3 to ground (not any other pin) should have 12 v. Next, switch in M1 and test Pin 2 to ground. Then M2 and check Pin 1 to ground. Finally, High and Pin 6 to ground.
Ohmed out the resistor pack6-3 2.8 ohms 6+2 1.1 ohms 6-1 .5 ohms
did the voltage test and only thing read was -3-g 11.49 voltage
all other pins dis not read at all. Soaybe the switch itself?
Forget about the resistor... put is somewhere and leave it there for now.
As Saudade mentioned, focus on the terminal connector you took off the, uh, thing we aren't talking about right now.
You should get 12 volts between terminals 3 to Ground any time the system is set to AC, heat, defrost, etc. Regardless of fan switch setting.
Starting from the lowest setting, when you set the fan speed on the next setting up from the lowest, or first notch up, you should read 12 volts between terminals 2 to Ground.
Notching the fan speed up one more, just shy of the highest setting, you should read 12 volts between terminals 1 to Ground.
Depending on your vehicle's option/exact wiring, you may or may not get 12 volts between terminals 6 and Ground. We can deal with that later.
The exact voltage you are reading isn't important right now. In fact, you can use a test light. If you have verified the three things above, then your fan switch works on all speed settings that involve the thingy we aren't dealing with right now. If you don't, then go to the fan speed switch on the back of the HVAC control in the center of the dash board and repeat these tests. Only, you will have to back-probe its connector.
12-25-2021, 05:15 PM
