96 Jeep Grand Cherokee electrical issue

[Eric Larson Kimbrow Jr.]

I recently purchased a 1996 Jeep Grand Cherokee, used ofcourse.

Everything on the Jeep worked just fine at the time ofpurchase with the exception of the heater blower, which the dealer repaired.

After repair the heater/air, regardless of how hi you twistthe knob, would only just barely come out of the vents, and even then, the onlyvents that really seemed to have much flow were the defrost and the floorvents, at one point only cold air would blow.

It was suggested that this was a vacuum issue or that thegates were not opening/closing but this was disproved and you can very clearlyhear the “thunk” when you turn the heat on. When the system worked howeverthere was still the issue of only working at a fraction of the pushing power itshould have had.

This issue continued for roughly a month and I was intendingto take the vehicle in to have this specific issue corrected by the dealer asevery other shade tree expert, including myself, has come up empty handed intrying to understand the specific issue.

5 days ago the heater died completely, the display went out,you cannot even hear the fan running… It’s dead Jim. So I proceeded to trackthe obvious problems and solutions and found the fuse for the heater was blown,I replaced it, it blew again immediately, I replaced it with a higher amp fuse…it also immediately blew.

The dealer asked me to bring the vehicle in and as I wasdoing so today, I mean, literally as I was backing out of the parking spot togo to the dealer, the radio died, the interior lights died, my turn signalsdied, and power seats no longer function.

I managed to make it to the dealer and as expected one fuseon the small board was blown and then it was discovered that one of the 50 ampsunder the hood was blown, these were replaced, however, the heater still doesnot work, the turn signals do not work, my interior lights do not work etc… Itis worth noting that these blown fuses were all checked as recently as 3 daysago and were in fact in tact at the time.

For some reason the Jeep is blowing fuses on these specificsystems and we cannot seem to track the issue.

When I was attempting to fix this problem when it was simplythe blower motor that was not functioning all signs pointed to either the motoritself being blown or the resistor behind the instrument panel being blown.

So my question is this.

What is wrong with my Jeep?
If I replace the blower motor or resistor will this correctthe electrical issue? Meaning to say, is it possible that the issue with eitherof these two could create an environment that would then cause other systems tobe affected in the manner in which I have described? And if so, when the motoror resistor is fixed will that give me back the functions I have lost?

Other “fixes”: It was suggested that I check the cabin airfilter to make sure it was not clogged and thereby obstructing the fan to thepoint of causing an overworking issue that blew the fuses and started thecascade. My Jeep is not equipped with a cabin air filter but there was a gooddeal of debris present in the trap, certainly not enough to restrict airflowhowever. The debris has been cleared but I am still left with the issues asdescribed above.

 

[greg92jeepxj]

Hey Eric welcome to Jeepz.com . Although I cannot directly help with your model , I will tell of issues I had with my '92 cherokee which is not as complicated a build as your '96 grand .
I have vacuum control vents , you probably have blend door actuators. I have a simple , inexpensive blower motor resister , yours is more $$. Also , my jeep dosen't have a body control module which takes over many tasks for the pcm which your jeep may have . But one thing that gets my attention , blowing fuses . I had an issue once that blower fan fuses would blow immediately. Turns out the blower motor resistor created so much resistance due to corrosion that the 12 gauge wiring from dash controls to the resistor shorted. The blower switch even melted. Fixed the wiring , replaced the resistor and blower switch , all was well . But bundled in the blower speed wiring was the a/c thermostat wiring to pcm and low pressure switch . A/c thermostats kept blowing . Found the fault , corrected it , all is well. It's clear that a wiring diagram is needed which you may have looked at and others too but in my case I couldn't do the repair without it or at least nearly as quick. I believe that since the blower motor has the one speed issue as would any blower with a bad resistor , wiring may be a factor and need inspection . I realize there is great difference between your Grand and my XJ and model year as well but the faults sound similar . I could have eventually repaired my jeep without a wiring diagram but would have been a lot longer and maybe a lot of unnecessary disassembly . But I strongly recommend you get every sheet of wiring diagrams involved with your jeep as its vastly more complicated than mine. Yes , these diagrams do turn you in circles by telling you to see this sheet , this splice , and so on but there is no other way on a grand cherokee as they are just more complicated. I wish for someone who has experienced this on their model year close to yours post here as you've asked but wanted to share my experience with you as mine was real world and may lend toward your repair. Best of luck and thank you for your membership . Greg

 

[drewbuddy]

I have a manual, I''l try to take a pic and post a wiring diagram. For the vents, may have to check your actuators behind the dash/nobs that control vent settings. Had an escort that disconnected so didn't work right, was doing what you described. would work a little but not right. Definitely a resistance or short if your blowing a 50A fuse. Too high of a resistance in the motor could slow air flow if motor too working hard. As well check the vent channels, they may have come apart when switching the blower motor causing improper flow. It kind of sounds like the dealer messed thing up more than fixing anything. Did you have any of these issues before you took it in for repair? If you had a meter you could check where the resistance is coming from

 

[drewbuddy]

Ok so no schematic for heating circuit in the manual and no actuators for control, is vacuum lines
Manual is lacking for this, but this is what I got, hope it helps
I would check for shorts, maybe wires melted or something, but need to look for this. Blowing 50A, you don't want to harm your PCM/ecub
CIRCUIT CHECK
1. Check fuse and all connections in circuit for looseness and corrosion. Battery fully charge
2.Trans in park, turn ignition to the on position(not running)
3. Blower motor located underGlove compartment area of the dash, near firewall. Bend back the clip on one of the blower motor mounting screws and release the wiring harness, pulling it down for easier disconnect.
4. Connect a voltmeter to the blower motor(harness side) connector
5. Move the blower switch through each of the positions and note voltage readings. Changes in the voltage indicates that the motor speeds will also vary as the switch is moved to different positions. Slower speeds will deliver less voltage to the blower, and the high position will bypass the resistor to supply 12v
6. If there is voltage, but the blower motor does not operate, connect a jumper wire between the motor ground termimnal and a good chassis ground. Connect a fused jumper between battery+ and the pos+ terminal on the motor side of the connector. If motor now works, remove jumper, and if stops working when ground removed, check for bad ground and re-test. if motor still doesn't work motor probably faulty
7. If there is no voltage at the blower motor, remove the resistor block connector and check it for voltage(at each speed). If there is voltage at any of the connector terminals, check resistor block for continuity and the wiring between the resistor block and the blower motor for an open short.
8 If there is no voltage to the resistor, remove the heater control panel,and with the ignition on, check for voltage at the connector for the blower motor switch.
9. If there is no voltage at the blower switch, check the wiring between the fuse panel and the switch for an open or a short.
10. If there is voltage, connect one end of a jumper wire to the terminal of the switch connector with voltage. Connect the other end of the jumper to each of the terminals that supply voltage to the resistor block. If your motor now operates normally, replace the switch

 

[ehab.taki]

 

[Roland Venne]

I was wondering if you figured out the problem? I'm having the same issue on mine. Not blowing fuses, but have one that has no power and nothing in the center row works.

 

[cougarlasch]

im wondring if the fan is wired the right way. being its the dealer and the dealer doesnt always use factory parts. and aftermarket blower motors come with 2 wires that need be connected to a pigtail connector. maybe the motor was wired in reverse polarity causing it to spin backwards causing the low air flow through the vents. and possibly the two wires are shorting together poor repair that is not insulated.