Forum Discussion

jeffo's avatar
jeffo
Explorer
May 21, 2017

Battery Idiot Light On

(2013 F53) First trip of the season and the battery light is on, checked the voltage of the chassis battery and did a load test and it checked fine with 12.5 volts (Not running)and 13.5 volt running. I did not think of checking the house batteries but I guess they charge from the alternator also. The house batteries seem to be fine, holding charge and reading full charge on the house meter. 13.5 is not as high as I would like to see it but I wouldn't think it would be enough to throw the light. Took it camping this weekend (30 miles from the house) and it starts fine and everything works fine.
Class A

8 Replies

  • jyrostng's avatar
    jyrostng
    Explorer
    May 25, 2017
    on top of the alternator is a push-on connector, pinch it to make it a tighter connection
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    May 22, 2017
    jeffo wrote:
    Does anyone know where the sensor would be located?

    There is no "battery sensor" on any Ford vehicle that I have ever seen. Yes, both the PCM and the alternators internal voltage regulator both look at battery voltage. The voltage regulator use the "A" terminal on the alternator, while the PCM just uses its normal 12+ input pin.

    The PCM "commands" the alternator to output a certain voltage. The Alternator responds with "yes, I am" or "error".

    If error is reported, the PCM sends a message to the dash to turn on the battery light.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    May 22, 2017
    The battery light works one of two ways.
    One way is to be hooked between the battery and the alternator field winding. When the alternator is working, the way this works, no current flows through the light. but when the alternator is sucking power rather than delivering itk current flows and the light lights.

    The other way is for the engine comnputer (ECM) to turn it on and off. And there.. Well that's above my pay grade.
  • jeffo's avatar
    jeffo
    Explorer
    May 22, 2017
    I did the load test with a Load tester. It basically puts a major draw on the battery for about 15 seconds and then checks the recovery voltage. I will do a gravity test on all the batteries. When I checked them the other day I really was not thinking about the house batteries having an effect on this. I did check the water level and they were good. I haven't check the water level in the chassis battery, it's a little hard to get to. Does anyone know where the sensor would be located?
  • traveylin's avatar
    traveylin
    Explorer
    May 22, 2017
    4 years on an oem battery putting 12.5 volts would cause me to replace the battery first. House battery replacement not to distant in your future also
  • ArchHoagland's avatar
    ArchHoagland
    Explorer
    May 21, 2017
    Have you checked the water levels in ALL of your batteries?

    I'd suggest checking the cells on all the batteries with a hydrometer.
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    May 21, 2017
    jeffo wrote:
    (2013 F53) First trip of the season and the battery light is on, checked the voltage of the chassis battery and did a load test and it checked fine with 12.5 volts (Not running)and 13.5 volt running.

    I am not sure how you do a "load test", but, with the engine off, I just turn the high beams on for about 5-10 minutes. Then connect the voltmeter and start the engine. You should be getting 14.0-14.5V volts. It may drop down to just below 14Kawasaki Diaphragm,carburetor - 43028 - 3704, but 13.5V sounds pretty low especially if the battery is partially discharged.

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