DBGrif97

Hello to all of you- new to these forums. I just want to mention first that I plan to be as active as I can here, as opposed to just bolting in and out whenever I need something. I have memberships on other auto forums and I know that type of behavior isn't always appreciated. I'm a decent backyard mechanic and a fast learner, but I'm not very familiar with jeeps.

Which brings me here. It's my wife's vehicle- a 97 Cherokee Sport, with about 130k on the I6 4.0 engine.

First of all, we can hear a knocking/thumping sound at idle from the cabin after the engine is up to temp. I've tried isolating it but haven't had any luck, because if I pop the hood the other sounds of the engine drowns it out. I suspect the knock sensor is the cause, but I don't know where to look for it or how to test it.

Second, we're having issues with the windshield defrost. If the fan speed goes over 1, the diverter flap will shut and block air from defrosting the windshield, and it won't open again until the heater is turned off. When it first started happening last year, I traced and checked the vacuum lines for the heater control for leaks. When I couldn't find any, I rigged open the flap, telling myself that I'd get it fixed before next winter. Well next winter is here and I still haven't done anything about it. I didn't know if this was a common problem and what I might be able to do to fix it, because the best I can tell is that the mechanism that controls that flap opening and closing has gone bad, and it looks like I'd have to tear into the dash pretty far to replace it, if I can find a replacement at all.

Next up is the windows. All the windows will work on the master switches, but only occasionally will they work on the individual switches. There doesn't seem to be any particular set of circumstances to make them work or not individually, and I'm sure the window lock is not on.

Last but not least, the fog lights aren't working. The fuse is good, and I don't really know what else to check.

Thanks to all for your advice.

Throttle Jockey

thats quite a list. its probably best to handle them one at a time. the knock sensor is there to detect "labor knock" or "spark knock" and the computer adjust the timing accordingly. a knock can be hard to isolate. may need more input on this issue. the defrost issue, perhaps some one more knowlegible on this topic will chime in. (sorry). the window buttons. all the windows work from the drivers seat but randomly dont from the respective buttons. its your wifes DD right? if she is the only one operating the windows from the driver seat, the other buttons dont get used all that often, they will get dirt/dust in them. you might try pulling the switches out and cleaning them. the fog lights are a simple circuit. if the fuse is good check for power at the switch and the relay and make sure you have a good ground.

DBGrif97

Thanks for the response. Yes, it's my wife's DD. I will try giving the switches a good cleaning and see what happens. I guess I didn't think to check for power to the switch for the fog lights.

Can you tell me where the knock sensor might be located so I can try testing it?

gpXJ

I don't have time to search as I'm on the way out the door, but just last week someone posted a how-to on rebuilding the fog light switch. You should be able to do a search and find that thread. There is also one on the windows only working from the driver's switch. The work-around is jumping across the connector (which can be found on the floor behind the panel just in front of the door) with a paper clip. This disables the lock button, but they will work from all switches.

gpXJ

Actually I found the window one......here you go

https://www.cherokeeforum.com/f2/win...working-13287/

DBGrif97

Thanks for the link, gpXJ. But if the problem is with the window lock switch, I think I'll try fixing/replacing it first, because I'm not too thrilled by the idea of using a paper clip as a jumper wire. It may work just fine but it sounds like too much of a fire hazard, if not just a surefire way to continually short fuses. At the very least maybe I can put together an actual jumper wire to go between the leads.

I tried searching for the fog light switch rebuild thread but couldn't find anything. I tried a few different terms for it and still nothing. Maybe I'm just not using the right words.

Does anybody else have any ideas on the defroster issue?

gpXJ

Yeah. I meant to add that to my post, just ran out of time (wife yelling in my face to come on, we are leaving). I would definitely suggest soldering in an actual jumper wire, if cleaning and/or replacing aren't an option. I wouldn't use the paper clip in my rig either.