Pelican Parts: Alternator Problems

Question: My alternator lamp keeps coming on. How do I know what the problem is?

Answer:
     First some facts about the alternator. The stock alternator that came installed in the 914 is a 50 amp Bosch model that is cooled with a special rubber boot attached to an outlet from the cooling fan housing. Sometimes the charging system may be unreliable if the voltage regulator has failed. The best way to check the regulator is by checking the voltage output to the battery during engine operation. Also, you can check the regulator by replacing it with a known good one as well. The regulator, or governor as the 914 manual calls it is located on the 914 relay board in the engine compartment. If the regulator fails, it may overcharge the battery and cause battery acid to spill. Make sure that this is cleaned up immediately, as it will corrode the metal in the tray and the surrounding areas as well. Baking soda dissolved in water will help to neutralize the battery acid if it spilled.

     Before even thinking about replacing the alternator, be sure to check all the ground connections, especially the ground strap attached to the transmission. Also be sure to check the alternator belt for tightness, and replace it if it is cracked and worn. The correct replacement size is 9.5 x 965(mm).

     If you are having trouble with the alternator light, check this list to see if you can diagnose the problem:

Alternator indicator lamp is on with key off.

Alternator has failed, and diodes have shorted out. Replace alternator and in the meantime, disconnect battery to prevent complete draining of the battery.

Alternator indicator lamp does not light when key is turned on.

Alternator bulb has burned out.
Regulator has failed
DF wire is disconnected or broken from alternator
Alternator has failed, and internal slip-rings are open

Indicator lamp remains on after engine is started and running above 2000 RPM

Regulator has failed
Battery lead to alternator has been disconnected
Alternator is not firmly grounded
Alternator internal slip-rings are dirty or worn
Indicator lamp wattage is too low (not enough initial current)
Alternator is bad

Indicator lamp is dim after starting, and gets brighter as engine RPM increases.

Battery lead to alternator loose or bad
Ground connections are bad
Battery is bad
Alternator is bad due to open diode failure

Indicator lamp is dim after startup, but eventually gets dimmer and goes out when engine RPM increase.

Low charged battery
Poor connections to battery

Indicator lamp is dim after startup, and gets dimmer as RPM increases, but never goes out.

Regulator has failed
Alternator is failing

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Pelican Parts: 914 Questions & Answers...