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Engine runs off the battery.


blsmith's Avatar
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03-07-04, 06:38 AM   #1  
blsmith
Engine runs off the battery.

Hello, I am new to the forum and hope I can find some help.

I have a 93' Town Car. 4.6 L engine. 205K miles. It was running ok for a go to work car. While driving the battery indicator light came on and the battery started to discharge until the engine died. To me, this was an indicator of alternator problem. It did test as bad. The battery was marginal and since I could get a free replacement, I changed it. With a new alternator, new battery and new positive and negative cables. The car starts right up, but I am still not running off of the alternator and charging the battery. I had the new alternator checked, it is good. It continues to run off of the battery. The voltage regulator is built into the alternator. I am not an auto electric whiz, but I have worked on cars for many years and have never been this stumped. It is probably something simple that I am over looking.

Any help would be appreciated.

 
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03-07-04, 07:59 AM   #2  
Hi welcome to the Forums

With engine off use a volt meter and measure the voltage at the big batt wire on the alt, you should have battery voltage there.

 
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03-07-04, 03:53 PM   #3  
Re: Engine runs off the battery.

Originally posted by blsmith
The car starts right up, but I am still not running off of the alternator and charging the battery.
What do you mean by that? Do you have a light on or did you have the voltage tested. What are you basing this on?

 
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03-07-04, 05:25 PM   #4  
blsmith
The battery icon light on the instrument panel will not go out . After the engine runs for a while (driving or just idleing), the headlights dim, the electronics start to beep and go out, the engine dies and the battery is discharged. This would normally indicate a bad alternator. This is a new alternator and it retested OK.

Previously, I installed the alternator from my 92' Crown Vic (same alternator and engine) same discharge results and it retested ok. I put it back in the CV and it charges ok.

Something is stopping the Town Car starting system from switching to the ignition system. The spark plugs are firing off of the battery and not the alternator.

 
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03-07-04, 05:34 PM   #5  
Like I said check the batt term for voltage.

If you have the CV disconnect the alt plug with the 3 wires and turn the key on, find the terminals on the harness side that have power.

Go to your TC and do the same and see if you have the proper voltages.


Maybe a fuse?

 
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03-07-04, 05:48 PM   #6  
blsmith
toyotaman, I am going to follow your advice. I had Granddaddy duty today. So I will make the check after work Monday.

 
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