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Discussion Starter · #1 ·
Greetings, Gents:

I'm having a problem with the electrical system in my 1991 Legend sedan. Any advice you could give me about trouble-shooting this problem would be greatly appreciated.

For the past several weeks, the car has intermittently refused to start after having been warmed up and driven. (I live in the northeast, where the temps have lately been between 30 and 45 F--I don't know if our region's falling temperatures have anything to do with the problem.)

Three days ago, the car did nothing when I went to start it in the morning. No click of the solenoid, no cranking, no interior lights or radio . . . Nothing. The car started fine when I jumped it. It drove without a hiccup when I took it to have the battery looked into.

I figured the car had a dead or weak battery and drove it to a battery service center. They tested the battery, told me the battery was bad, and installed a new one. I'm not sure if they tested the car's charging system. At any rate, with the new battery, the car started fine and drove normally over the next few days.

This morning, when I went out to start the car (outside temperature about 30 F), I found myself back to square one: no click, no crank, nothing.

Any idea what the problem might be? Main relay, alternator, etc.? Kindly let me know what part of the electrical system I should trouble-shoot first.

As always, I appreciate the help.

pa.legendman
 

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Discussion Starter · #4 ·
Additional Diagnostic Information

Hello again.

I have additional data to offer concerning my 1991 Legend's faulty electrical system.

In answer to your question, I did not have the battery cables replaced when I purchased the new battery. A bad alternator struck me, too, as a diagnostic possibility: but I'd like to trouble-shoot the problem myself in case some other unit--say a main relay, which I can easily replace as a DIY project--is at fault.

I just had the car jumped, and the symptoms it displayed left me puzzled (though I'm admittedly no expert and possess only a rudimentary understanding of my vehicle's charging/electrical system).

Before I jumped the car, the battery behaved as if it were completely dead: absolutely no power, no lights, no power window/seat use, etc. It was as if the battery had no juice at all.

Attaching jumper cables from a running vehicle's battery to my battery restored electrical power to the car (lights, windows, power seats, etc.). However, I had to crank the engine 15 to 25 times before it finally turned over. Most of the time, when I turned the key, the engine didn't crank. It just made an initial starting sound and then cut off after about five seconds. The car wouldn't let me crank and crank the engine until it turned over.

Once I got the car started, I let it run for about ten (10) minutes to let it reach operating temperature. I then shut it off without driving it anywhere. Once the car was off, all of its electrical items (power seats, lights, door locks, etc.) worked without a problem. I even started the car twice again: it fired right up both times--admittedly with a now-warm engine.

I was wondering if the car might be having a problem with its main relay. Would you expect the car's lights, etc., to work, with the engine off, after "recharging" a dead battery for only ten minutes--especially considering that a defective charging system was supposedly responsible for the dead battery in the first place? Then, too, I don't understand why I had to crank the engine so many times today to start the vehicle, while it was being jumped, if the car's only problem was a dead battery/defective alternator. Any light you guys could shed on this subject would be appreciated.

Finally, what are the typical symptoms a car displays with a dead/dying/defective alternator? And does anyone have any tips about how I can reach the alternator's 4P connector? I own a service manual for the car, and the diagnostic algorithm requires disconnecting the 4P connector at the rear of the alternator. I can hardly see the connector (there appear to be two of them, one colored green, the other grey or black, on the back of the alternator) and am having difficulty reaching it from the top of the engine compartment. (The space is too tight to admit my arm.)

Thanks again for your considerable help. :)
 

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To check the alternator:
With engine off, check the battery voltage at the battery terminals with a meter. It should be close to 12 volts.
Start the engine check the voltage again at the battery terminals. It should be around 14 volts(13.5-14.5) if the alternator is charging. If it's not working the voltage will be less than 12V.
 

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Discussion Starter · #8 ·
Additional Diagnostic Data

Hello again.

Another update on my car's ongoing electrical problem.

I went out this morning (ambient temperature about 30 F), tried to start the car, and again found it completely dead. No lights, power windows or seats, and no click when I turned the ignition switch.

Yesterday, after I had the car jumped and allowed it to warm up for 15 minutes, it started right up several times (after being turned off, albeit with a now-warm engine) and had working lights, windows, etc. even after I had shut the engine off.

Today, when the car was dead, I measured the voltage across the battery and got a reading of 0.25 volts.

After having the car jumped (it took several attempts before the engine turned over), I warmed the car up and measured the voltage across the battery. 15 volts. Does this mean the alternator is working (viz,. recharging the battery)?

After letting the engine run for 15 minutes, I turned the car off and found: 1: that the battery had recharged enough to run the lights, etc. with the engine off; 2. the voltage across the battery terminals measured 13 volts (I can't believe it had fully recharged after on 15 minutes); and 3. I had no problem restarting the car (though admittedly with a now-warm engine).

After all this, I took the battery out of the car and measured the resistance between the positive and negative battery cables. The resistance was somewhere between 0 and 100 ohms. (I didn't obtain an exact reading.) I was surprised by this finding, since I had expected the resistance between the two cables would be infinite. (If it weren't infinite, wouldn't the battery, under normal conditions always be discharging?)

At the moment, I believe my electrical system has some form of short circuit that is causing the battery to discharge (when the vehicle is switched off). What besides a short would cause a battery to discharge like this? Other possibilities include a bad voltage regulator and an intermittently operational main relay.

When you examine my car's symptoms and the results of the above tests, where do you suspect the problem lies?

Thanks for your assistance. :bowdown:
 

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Discussion Starter · #10 ·
Problem Solved: Shorted Rear Power Antenna

Greetings:

Wanted to let everyone know that, with your help and the assistance of other posts listed on the Legend Forum, I managed to solve my car's dead battery/electrical problem. The motor in my car's aftermarket rear power antenna had shorted out and was draining the battery.

Yesterday I performed a battery drain test on my vehicle and discovered that Fuse 56 in the underhood fuse box was drawing an inordinate amount of current (with the engine and accessories turned off). Fuse 56, I learned from the car's service manual, supplied the car's rear power antenna, which, not coincidentally, had stopped working a week or two before the car's battery went dead. When I removed the power antenna from the vehicle--viola--no more battery drain! Problem (thankfully) solved.

Couldn't have done it without members of the Legend Forum. Thanks to all for your help.
 
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