Is my alternator going bad?

[RECHRGD]

A couple of weeks ago I noticed that the ammeter showed a lot more charging and discharging than normal.  At idle it showed that it was discharging, especially if any load (electric fan) was on.  Once I gave the car any gas to accelerate it would show that it was charging more than normal.  On the highway all seems normal with the ammeter sitting at dead center on the gauge after a few miles.  I replaced the battery with a new one and had been on several long drives with it, so it should be fully charged.  But, it's still acting the same.  I know that this sounds like normal operation, but it's just that the needle on the ammeter is moving at least twice as much in both directions as it did before.  Could the alternator be the problem?  Thanks,  Bob

[firefighter3931]

Bob, i'd be more inclined to think that it's the regulator. Are you 100% sure that the battery is FULLY charged ? If not....i would start by running it on a battery charger overnight. The re-test the next day with a known fully charged battery....if the symptoms return then start with the regulator. It's possible that your battery is defective....nothing these days surprises me. 


Ron

[RECHRGD]

Bob, i'd be more inclined to think that it's the regulator. Are you 100% sure that the battery is FULLY charged ? If not....i would start by running it on a battery charger overnight. The re-test the next day with a known fully charged battery....if the symptoms return then start with the regulator. It's possible that your battery is defective....nothing these days surprises me. 


Ron

Well, we went for a 400 mile drive last weekend after installing the new battery, so I would assume that it's fully charged.  But, you're right, even a new one can be bad.  Last season I changed out the regulator to the electronic type.  I'll throw the old one back on to see if things change.  Thanks,  Bob

[RECHRGD]

Well, I swapped out the regulator and no change.  I'll have the alternator and battery tested next week.  Although the alternator is obviously charging, it seems to have little or no charging capacity at idle.  Just the brake lights when stopped at a light drag the needle well down in the minus zone on the gauge.  It never did that before.   Bob

[RECHRGD]

Well, it's fixed.   The alternator tested bad.  I had a hell of a time with NAPA people trying to get the right one.    Maybe I'll post about that in the car guys section.  Bob

[firefighter3931]

Well, that wasn't too difficult.....other than sourcing the correct alternator. 

Good to hear you have it fixed Bob 



Ron