red flashing alternator light

   / red flashing alternator light #1  

labopr

New member
Joined
Feb 15, 2005
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The battery on my Ford 1600 diesel was 7 years old and had to be charged before I could start in cold weather so I replaced it. With new battery everything works fine...glow plug and start up but the alternator light flashes after about 1 minute of running. What is going on? Thanks
 
   / red flashing alternator light #2  
Maybe the alternator is going bad.. or is bad. While your tractor is running.. disconnect (+) battery terminal.. the tractor should still run from the alternator's current. If it dies.. your alternator's bad.. and the old battery was probably still good.. but just dishcharged.

Hmmm.. now I'm thinking.. does this method only work for gas engines?
 
   / red flashing alternator light #3  
that test only works with gas engines
 
   / red flashing alternator light #4  
You need to check the battery voltage at a high idle. Should be between 13.5-15 volts. Anything lower is bad alternator/generator or regulator. Of course you will need a volt/ohm meter.
 
   / red flashing alternator light #5  
I had a strange case where I replaced the instrument cluster because of a fogging problem. Not only did the new cluster fog too but the alternator light flashed intermittently at me from time to time to annoy me. /forums/images/graemlins/mad.gif

Putting the original cluster back in place stopped the alternator light flashing.
 
   / red flashing alternator light #6  
</font><font color="blue" class="small">( that test only works with gas engines )</font>

It works with diesel engines that have a fuel cutoff solenoid as well...

Soundguy
 
   / red flashing alternator light #7  
Labopr
Welcome to the forum.
Let's start with the easy things first.Check your belt for slippage. Make sure your connections are clean and tight. If these are ok then put a volt meter across the pos. & neg. terminals on the battery,with the machine not running you should have 12 volts.Start the machine and the voltage should rise to 13.5/14volts.If this is verified then the alternator /regulator are o.k. if you don't have this rise in voltage then either your alternator or regulator is not working and needs repair/ replacing.If you still have a flashing red light with the correct voltage readings look for a short.
Good Luck
 
   / red flashing alternator light #8  
As a rule of thumb DONT EVER DISCONNECT A BATTERY from a running machine. Two reasons why:

1. When a person does that it can create a syrge that is strong enough to destroy an alternator. It was an old trick that worked with the generators of yesteryear.

2. Any spark at the right moment, with the right amount of escaping gas can cause a battery to BLOW UP in a person's face. A very ulgy, possibly blinding and scarring situation.

I hear of hundreds of people that try this every year, especially mechanics. PLEASE PLEASE don't.

Here is the proper way to check a battery and charging system.

1. Visually check for the obvious, broken or disconnected wire to the battery and alternator.

2. With engine off, check belt tension. You should not be able to turn the alternator's pulley. Do not overtighten the belt because that will lead to bearing failure in the alternator.

3. Remove the battery, charge the same battery on a slow or trickle charge, for at least 8 hours.

4. Same battery still, have it "load tested" at your local parts store or repair shop. Literally a 10 second job.

5. If battery checks out OK, reinstall and check alternator's output voltage off idle. Should be at least 13 - 15 Volts. (Most usually do at idle)

6. If all checks OK, then the diode in the alternator, sending the signal to the "dummy lamp" is on its way out. (Hence the word idiot light - still charging but says no at the same time)

A guess would be that the battery is bad. A bad battery will cause an alternator to show a lower charge voltage and even cause an alternator to fail eventually.

I hope this helps.
 
   / red flashing alternator light #9  
Bugsy..... you nailed it perfectly.... I couldn't have said it better. To add to this, one thing that will kill a battery quickly is not having it properly secured in the battery box. My experience with diodes is that they are either good or bad, but never in between. An alternator will continue to perform even with a defective diode, but just not up to par. I would take the alternator off and have it bench tested. Also, check the wiring on the "idiot light" to make sure that it doesn't have an intermittent ground. If the flash is uniform in duration, then I blame the alternator..... if not, then I look for other wiring abnormalities....
 
   / red flashing alternator light #10  
Another possibility is the new battery is undercharged. Just because it's new, doesn't mean it's fully charged. The glow plugs draw a considerable amount of current and if the battery is undercharged, the alternater will be maxed out trying to restore it.

Try charging the new battery for a few hrs...it might be as simple as that.
 
 
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