I have an ongoing issue with my 98 discovery. My interior lights, as well as, headlights flicker/pulsate and I don't know why. Originally 2 months ago my car wouldn't start and found out it was the battery. I replaced it but the flickering continued. Last week I was driving at night, go a phone call so I pulled over to take the call, had the foot on the brake and it died after a couple minutes. I tried starting it and it just made a loud clicking noise in the passenger side. I tried jumping it that night and it wouldn't start (instruments lights came on while trying to jump it). The next day I went back to where it was, tried jumping it again and it initially didn't want to start but I pressed on the gas and it turned over and started up. I took it to an auto shop and they had it for 2 days and said they couldn't find why it did that. After asking them to keep testing it they said there was an intermittent signal with the cam shaft sensor and they changed that and gave it back to me. Last night was the first night driving and noticed the lights are still flickering. Does anyone have any ideas? It would be much appreciated.

Bruce

 

IMHO you have an electrical problem that is one of these:

the alternator internal regulator is failing, it can be rebuilt by a local indy alternator / starter shop or you can buy a reman unit from some place like Autozone, however, if you buy a reman unit they have a high failure rate. Be sure to get one with a lifetime warranty, etc., may only last 6 months. The part is shown below, it is like $60 from BP Utah, and is a DIY swap under the back plastic cover on the alternator. Be sure to take (-) and (+) battery wires off before replacing. (pix 4)

The black cable from the battery is loose at the battery (shop should have cleaned that) and directly below where it bolts to the frame under the corner of the radiator.

One of the two wires at the front of the underhood fuse box is loose or corroded. These have to be clean and tight. One brings amps from alternator to the fuse box, the other connects battery to the fuse box and alternator. (pix 2)

The small wire from the fuse box to the (+) battery terminal is loose or corroded at the battery terminal end. (pix 3 - small wire under red battery lead cover)

A wire that is secured to the back of the alternator on bolts is loose.

If you have a test meter you can monitor voltage, the expected volts are from 13.8 - 14.4 when truck is running, as you turn on more devices (lights, wipers, AC) the volts will drop, but should stay above 13.2.

If you are not "electrical" or if you are a road warrior stuck out of town while SWMBO is dealing with this Disco problem, or you just want something that you can use to monitor the electrical system, this plug in tester goes in the cigar lighter, and will display the volts as you drive. Just under $20 at WalMart. The picture shown is a D1 with everything on. (pix 3)

 

Bad alternator.
I had one that did the exact same thing.

 

I would suggest you not buy a rebuilt alternator from a local parts store, so many of them fail within weeks, consider going to British Parts of Utah and buy one of tthe 3 different ones they offer, 1 new and 2 rebuilt from good companies.

 

Heres a story of mine that might help u or anyone else. I had the same problem with my 1997 DII. Thinkin it was the alternator I got it tested and it was fine. Then by backtracking the latest electrical repair before this problem. I had replace the battery with my other car since I wasnt driving it. It was working fine for weeks till the flickering. I bought the correct battery and drove for about 10mins and now no flicker. hope this helps someone.

 

Yep, bad alternator!
This reminds me to change the "temporary fix" on mine.
My story: car didn't start right away, winter came and wery hard to start. changed 7 years old battery (with red optima), fine for a while then back to unenthusiastic starting. Started monitoring charging, running and starting voltage with cigaret lighter meter, no satisfactory diagnosys.
monitored voltage difference between alternator positive and battery positive, erratic flactuations: renewed wire connections to alternator.
Finally SWMBO was FORD (found dead on road) the car, not her! with dead battery. I got pissed and took apart the alternator: Duh! Worn brushes! Went to nearby corner store and got 2 "D" cell carbon batteries and broked them open to take the carbon core. Filed the round core on the cement sidewalk to fit and inserted between the worn brush and the contacts on the rotor. It's now 6 years later, I better do something to the alternator brushes soon.
SD

Everything is possible, the impossible just takes more effort.