Alternator or Battery Problem on 87 XJ6 Series III

[Michael J.]

This one has me totally baffled.

I started noticing that the voltmeter, "Battery Indicator" would stay pegged at low end for several minutes after starting, gradually raising to indicate never more than about 12 volts.

Sounds like classic battery or alternator right?

Brought it to local part store. The put a tester on the system and determined alternator was bad. Replaced alternator.

Problem persisted. Thought it might be the guage. Now getting hard starting problems as if the battery is dead. Hydrometer has one cell lower than the others, but still in good range.

Sometimes starts smooth other times starter relay clicks.

Wiring diagram depicts four wires connecting to the alternator.

There are only two. This car has the Motorola Alternator rather than the Lucas.

What am I missing here?

Is this an ignition switch problem? That does not seem correct.

Suggestions anyone?

 

[kennypinkerton]

Clean battery terminals, have battery checked (free) on the machine at Advance/Oreiley/Autozone, Check the ground terminals for tight clean connections, check the battery cables for internal corrosion. Check to make sure there isn't something draining the battery overnight - interior lights, underhood/boot light, radio, etc.

 

[John S Farrington]

Go to your alternator connectors. The larger of the two wires should be battery 12 volts all of the time. The smaller of the two wires is the exciter voltage that should be 12 volts with the ignition switch on. If you had no or intermittant excitation voltage, the charging system could act as you describe. Also make sure that your alternator drive belt is tight. Jack

 

[Exotexs]

Re: Alternator or Battery Problem on 87 XJ6 Series

1) I have been told that when you replace the alternator, you also replace the battery, because the bad (old) alternator compromised the old battery, and because the old battery will then compromise the new alternator. Whether that is true or a Sales Gimmick, I don't know, what I do know is that the last time I replaced the alternator, I also replaced the battery and well, I have not been dissapointed.

2) in my '84 XJ-6, the voltage gauge is somewhat slow to reach up to the 12-13 volts mark as well, so I don't think it's the Gauge itself. As my mechanic friend says, it works or it doesn't...

3) you might service the two "POSTS" located at the firewall, (bulkhead), sticking out into the engine compartment from the interior, one on the left side, one on the right of the engine, covered by rubber boots. There are many wire bundles connected to these two posts by ring terminals. Undo each nut on each post after pulling back the rubber boot, (very carefully, the rubber is usually brittle), and with a Brass wire brush, pull and clean all ring terminals and then the post threads until shiny. this helped revive the electrics in my XJ, making everything brighter and livelier.

4) after you shutdown the ignition, turn all switches off and close all doors, check the rear lights to see if the Brake lamps stay on, you could have a stuck brake light switch. If it is bad, these switches can be repaired, so open it and try to fix it. Also check the marker lamps mounted on each door panel, if a door switch is stuck open or is shorted, the bulb will stay on, draining the battery overnight.

 

[Michael J.]

Re: Alternator or Battery Problem on 87 XJ6 Series

I ended up replacing the ignition switch after some other wierd behavior surfaced with the switch.

With the switch replaced things behaved as Jack Farrington described

Things are now back to normal.

Thanks everyone for the suggestions.

 

[Michael J.]

Re: Alternator or Battery Problem on 87 XJ6 Series

Update:

Found that the bonding strap was also loose.