electrical gremlins

Patient is 1990 Cherokee Laredo

Symptom is no cruise, no radio, and the dash clock is dimly lit.
Clock keeps time ok but never goes to full illumination.

Believing a ground prob checked under hood - battery ground and others on the right, also the woven strap and the left.
Just visual check and cleaning. No damage seen and was not that dirty.

Question is I seem to remember reading about this type of prob here or elsewhere and not able to find that info at this time.
What do these three have in common?

Also have a port on the air box that has nothing connected to it.
It is a 5/8 or 3/4 inch port on the top rear. The PCV hose is connected to another port, but I have seen pics with this upper port used for the PCV connection.
Any help greatly appreciated.
TIA
Troy

If your horn and fan don't work, it could be the ignition switch, try wiggling the key while in the ignition.

The large port at the back of the air cleaner box should connect to the breather tube at the front middle of the valve cover.

Engine?

If a 4.0, no PCV valve. It is a metered orifice CCV system. Filtered fresh air to the front grommet on the valve cover, manifold vacuum to the rear grommet that has the metered orifice in it.

No cruise could be vacuum related--there is a vacuum reservoir that is mounted behind the front bumper, passenger's side. There is a hard vacuum supply line that runs to it and likes to break around the battery.

Renix systems are real fussy about the grounds. Don't look at them, take them down to bare metal, treat with an anti-corrosive, and make them tight. Don't forget to do the dipstick tube grounds, and replace that POS braided strap to the firewall with a 4 or 2 ga cable.

Thanks for the replies.
Day off from work tomorrow.
Will remove and clean the grounds.
And the vacuum for cruise.
Is there anything common to the cruise, radio and clock?
Or are these individual issues to be solve one at a time?
The clock working but not lighting up all the way makes me think ground.
Dont have a wiring diagram to see if the power for clock memory is seperate from illumination power source. So my ground fault theory may be totally wrong.
Horn and engine fan work fine as does the Heat/AC Blower.
Hoping you guys can help with the TS this, will post pics tomorrow.
Thanks again for your help,
Troy

Engine 4.0L I6 Renix
Pics of under hood:
http://s193.photobucket.com/albums/z318/tagordon/Jeep/

Feel silly (read moron ) not noticing the CCV hose was just shoved behind the brake booster. Connected it back to air box. Also noticed the hose from the front diff is tied up behind the booster, what is the correct location to fasten this hose?
Have not found the vacuum hose for the cruise, been looking right side near and around battery. More guidance please.
Again, is there a common cause possible: or are the cruise, radio and clock independent issues?
TIA
Troy

That is the differential vent line, just needs to be up where water can't enter it.

Ok, there is (should be) a vacuum line off the manifold. It will provide vacuum to the HVAC system to operate the air box doors and it also operates the coolant control valve (by the pressure bottle--the rats nest of hoses). If you have the NP231 transfer case--2wd/4hi/N/4lo--you would have the D30 CAD front axle, a vacuum disconnect motor on the passenger's side that slides a collar back and fourth to engage/disengage the front axle depending on the transfer case lever selection. On the transfer case is a vacuum switch, it has a supply line to it, two lines off of it to the axle vacuum motor. There are three ports on the vacuum motor on the axle, engage/disengage, and the third port has a line that runs back up the firewall to a vacuum/electrical switch that lights up the dash 4x4 light when vacuum is applied to engage the axle. Back to the cruise, there should be a vacuum line that runs from the manifold, with a check valve in it, then splits off to the transfer case switch and the HVAC controls, then runs around along the passenger's side fenderwell and has a split off for the cruise then runs on down to the reservoir behind the bumper.

This reminds me that a niggling little fault that my '96 4.0 Ltd has had since I got it in January, is that while the clock works it's not lit.
From following this forum almost as long as I've had the Jeep I know that the clock shares a feed with the radio illumination - but that an aftermarket unit that only illminated when it's switched on.
Now before you all say it's simple, just trace the wiring back, that's what I would've done on anything else but one of the most irritating feature of these vehicles for me (an enthusiastic & fairly experienced amateur auto electrician) is it's almost inpossible to access/identify any of the wiring or remove anything without breaking it - I've not got the slightest idea, e.g. how to get behind the clock or where to find the other end of that wire.
C'mon guys, most of you have forgotten more about XJ's than I'll ever know.

A common failure mode of the clocks in those years was to lose illumination while still keeping time. I don't think it is related to your radio. It's just what the clocks did. My 90 has the same problem. Next time I'm into the instrument cluster, I'm unplugging the clock. I've got one in my radio anyway.

This tells you how to identify your clock and the various power leads: http://go.jeep-xj.info/HowtoDashClock.htm

I added a clock purchased off eBay to my '93 which didn't come with one. Pull the dash panel off and you will see how to access the clock. It has been awhile and I don't recall exactly but seems that you have to remove a couple of screws to get the cigarette lighter panel out and whatnot. Not difficult at all.

Your wiring situation will likely be different from mine since you already have the clock but it should be easy to identify the leads and, if necessary, find an appropriate illumination source from the nearby radio wiring as I did (assume you have a meter). I don't remember precisely how the wiring went but I do know that it was a quick and simple project compared to most in-dash adventures.

Come back if I've missed anything and good luck.

sorry about the delay in responding , it's not that I'm not grateful but some heavy family responsibilities mean that my poor ol' XJ has to do a 500 mile round trip every weekend but otherwise be completely ignored.

However I am more confused than ever now: Cruiser is virtually saying I'm wasting my time, replacing the clock with another similar one, whereas Pelican suggests picking up another power supply may be all I need do.

I've checked out that link before which on one hand suggests RHD XJ's don't have clocks but also contains some input from a fellow Brit who claims mine should have a model which it most certainly doesn't.

I've checked lots of threads about swapping dash panels & the like - but I remain completely mystified about how you start to remove it, or even gain access to the back of it.

Get the cigarette lighter panel out - how? I can't see any screws anywher near it!

As respects removing the dash panel, I don't know if there are any differences for RHDs , but for LHD, there are four vertical Phillips head screws to remove, one each over the headlamp switch and cigarette lighter and two over the instrument panel. The panel is just clipped in around the radio and HVAC controls. After removing the four screws, you can pull the panel straight out beginning wherever you can get hold of it, easiest being probably at the bottom left (for you) of the HVAC controls. The panel can be difficult to work loose around the top of the steering column but will come out with patience.

I didn't reread go-jeep's write-up prior to my previous post, but in one of the pictures, you can see the two screws at the top of the lighter panel that you can access after removing the dash panel.

I can't speak for xj clocks in general but it is true that the illumination failed after many years on the clock that was original equipment in my '85. I like having a clock separate from the headunit so added one to my '93 as mentioned. Works fine so far. I'll just put another one in if the illumination on this one fails.

Once you get the dash panel off, you should be able to match up the wiring per go-jeep's article and see if the illumination lead is receiving current with the ignition on. If the lead is hot (per meter or test light), the illumination function of your clock is presumably bad. If the lead is not hot, you can do what I did and drill a hole in the plastic panel behind the clock angled toward the radio and run a wire to the radio ignition-on lead.

I hope this all makes some sense. If not, don't hesitate to get back. Let us know how it goes in any event.

Not sure on RHD vs LHD issues... but GoJeep is in AU, so his page that Pelican linked may provide some info. Usually it's "remove screws until things fall off" and then you just get to figure out what order to put it back together in!

The VFDs (vacuum fluorescent displays) in many of the modules used in the XJ tend to wear out over time. I would not be at all surprised if the one on a '90 was dead, the odometer on my '98 is getting close to worn out and so is the clock in my '91.

As far as I can work out there's no real difference between LHD & RHD dash panels.

Pelican, for the reasons I was so slow responding before, no idea when I might be able to do more than to have a look to see if I can at least find these 4 screws, but hopefully before next May when I hope to be in Az for a couple of weeks &, therefore, in a much better position to, e.g., source a replacement clock for sensible money. Thanks for your patience in explaining how to approach the job: I will take you up on your invitation to get back to you - but I can't promise when.

Just out of curiosity did you check the fuse for the radio? I believe that the radio and clock are on the same line. Also check the fuse on the back of the radio itself.