Headlight power fluctuation

Any help from the “Cherokee Gurus”?
Having a small problem with the charging system on my ’98 XJ.
At night with the headlights ‘on’, I have been noticing at varying intervals the light intensity (voltage) momentarily dips. It happens so fast that if you ‘blink’ you miss it. After awhile it becomes annoying. There is no Malfunction Indicator Light ‘on’, so there is no other indication other than the light intensity ’blink’.
I have manuals for both the ’97 and ’99, but not for the ’98. Not being sure about the trouble codes access, I checked both the ’97 and ‘99’s manuals. As I interpret it, the ’97 trouble codes can be accessed by the on-off-on-off-on sequence. Apparently the ’99 needs the dealership’s DRB scan tool to access the ‘99’s trouble codes. I tried the ’97 sequence on this one and “nothing”… so apparently the ’98 shares the trouble code electronics with the ’99??
Anyone had a similar electrical problem or confirm what I stated above on the trouble code access?
Thanks

You will notice that it only does it when you have either your AC or defrosters on, both use the compressor. The dimming is caused by the momentary slowdown of the engine when the compressor comes on. It's normal....

RichP said:

You will notice that it only does it when you have either your AC or defrosters on, both use the compressor. The dimming is caused by the momentary slowdown of the engine when the compressor comes on. It's normal....

Click to expand...

RichP; I recently noticed a puddle of water under the r/f in the garage and upon checking it out found it was apparently condenser water dripping from the vent tube. I thought that strange because I have not (knowingly) been running the a/c compressor. But, I have had the defroster 'on' in the setting with the defroster/vent arrow position(on the right side of the dial).

Could you clarify for me just "when" there should be condenser drain present?
[1998]There are the two knobs controlling the heater. One has the heat/defrost settings to the right; and the a/c settings to the left. Nothing on the right side activates the a/c, does it? The other knob has red(heat) on the right side and blue(cool) on the left side. The blue side of this heat control is not using the a/c is it? Pardon the probably 'entry level' questions, but I'm trying to get a handle on when the engine would ecperience the a/c load (other than the obvious use of the a/c cooling mode)

Thanks Rich, really appreciate your help here.

your compressor runs when you have the AC on OR when the defroster is on.

dizzymac said:

your compressor runs when you have the AC on OR when the defroster is on.

Click to expand...

Does that mean that the "temperature" knob DOES NOT have control over the a/c compressor even if set into the 'blue' area to the left? (note that I realize the "mode" knob on the 'blue' area to the left obviously DOES directly control the compressor)

What I'm trying to get straight in my mind is: just when is the a/c compressor is not running...
How do I go about getting ambient air, at the outside temperature, into the vehicle (without just rolling the windows down) without running the compressor in one of the climate settings?

I thought I understood the vehicle's climate controls, but at this point I am wondering if the DAMN compressor will come on to some degree at any setting short of the "O" (everything off) setting on the 'mode' knob.

...Where did the wing windows from the 'good old days' go?... thanks again!

The vent/heat settings on the mode knob with the temp set to blue will bring in ambient air. As said before, the compressor runs on AC & defrost modes.

Lawn Cher' said:

The vent/heat settings on the mode knob with the temp set to blue will bring in ambient air. As said before, the compressor runs on AC & defrost modes.

Click to expand...

Got it! ...then it is correct to say, "the compressor runs [only] on AC & defrost modes"

thanks again!

idahjo said:

Got it! ...then it is correct to say, "the compressor runs [only] on AC & defrost modes"

thanks again!

Click to expand...

Righto!

idahjo said:

Does that mean that the "temperature" knob DOES NOT have control over the a/c compressor even if set into the 'blue' area to the left? (note that I realize the "mode" knob on the 'blue' area to the left obviously DOES directly control the compressor)

What I'm trying to get straight in my mind is: just when is the a/c compressor is not running...
How do I go about getting ambient air, at the outside temperature, into the vehicle (without just rolling the windows down) without running the compressor in one of the climate settings?

Click to expand...

The temperature knob has nothing to do with the a/c compressor. That is controlled by what you call the "mode" knob. Outside air WITHOUT a/c is available with the mode knob in the "feet" position or the "in your face" position. The "defrost" position turns on the compressor, as does the "bi-level" position.

Thanks ALL. I kept trying to figure out WHY I kept getting condensation drip on the floor when I had not had the a/c 'on'. DEFROST 'mode' was the culprit! (I was getting the idea the 'blue' side of the tempreature control might be causing it to run also)
NOW I UNDERSTAND

NO: 08-34-99
SUBJECT: Head Lamp Flicker
DATE: Oct. 8, 1999
OVERVIEW:
This bulletin involves installing a cooling fan relay module to reduce the current surge when the cooling fan cycles on.

SYMPTOM/CONDITION:
A momentary headlamp flicker may be present when the cooling fan or air conditioning compressor cycles on.

DIAGNOSIS:
This condition is difficult to diagnose and may only be noticeable in rural areas with no ambient lighting. If a customer indicates that the symptoms are present, perform the Repair Procedure.

PARTS REQUIRED:
Qty Part No. Description
1 05013440AA Relay Module


REPAIR PROCEDURE:
THIS REPAIR IS COMPATIBLE WITH DAIMLERCHRYSLER'S MOBILE SERVICE PROGRAM AND DOES NOT REQUIRE HOISTS OR OTHER FULL SERVICE FACILITY SPECIAL EQUIPMENT.



Remove the air cleaner cover.
Remove the air cleaner element.
Remove the air inlet hose from the air cleaner cover.
Remove the air cleaner housing from the inner fender well.
Position the relay module on the inner fender well as shown in Figure 1. Mark the locations for the four attaching screws.
Drill four 1/8-inch holes in the marked locations.
Coat the edges of the holes with a corrosion resistant primer.
Attach the module to the inner fender with four # 10 X 1/2 inch sheet metal screws.
Disconnect the cooling fan from the electrical harness.
Connect the relay module between the fan and harness.
Insert the connector retainer into the existing hole shown in Figure 1 to secure the harness.
Install the air cleaner housing.
Install the inlet hose.
Install the air cleaner element.
Install the cover.
POLICY:
Reimbursable within the provisions of the warranty.

TIME ALLOWANCE:
Labor Op. No. Time
08-65-12-93 0.2 Hrs.


FAILURE CODE:
Code Description
P8 New Part