Power issue

[randypmartin]

I replaced the alternator on my 1990 Bronco II about a year ago. The battery light on my dash has been on ever since but it never seemed to be an issue until recently. Have been experiencing low power especially when the air conditioner is on. Mechanic tested battery and alternator and both came back with good reads and the belt is nice and tight. The alternator I have is a standard 65amp. Did not check the output of the previous alternator before replacing it.

My main question is would putting a higher amp alternator in possibly help with a low power issue? Could it hurt to try? Very green when it comes to electrical issues and appreciate any feedback.

 

[RonD]

You need to invest in a $10 Volt/ohm meter

65amps is fine for 1990 BII..............unless you have added a BIG ASS sound system and some aircraft landing lights

Battery light shouldn't be on when engine is running

Battery volts, key off
12.3v to 12.8volts

Battery volts, engine idling
13.5v to 14.8volts

Any differences means an issue with the system

Battery light wire may have been accidentally grounded when new alternator was installed, this would make it stay on whenever key was on, even with engine running

Alternators have 3 Fields that generate electricity
Very common for a Field to fail, this would, of course, cause 1/3 "power" loss
i.e. dimming lights at idle and flickering lights
So if things were fine and then got worse its most likely new alternator starting to go

"New" alternators often have issues, so keep the receipt, they usually have a 1 or 2 year warranty, some are lifetime now

A new 95amp alternator may fix the problem but ONLY if the problem was the "old/new" alternator, not because you need 30 more amps

 

[Eddo Rogue]

Once again, Everything RonD said. Especially the bunk new alternator. Happened to me more than once

 

[4x4prepper]

Might be the voltage regulator. A bad one can fry a battery.

 

[rusty ol ranger]

Might be the voltage regulator. A bad one can fry a battery.

Should be an integral regulator...as in changing alternator means regulator too as its part of the alternator.

I had this happen years ago on a 351w LTD II. Granted being carburated engine performance wasnt affected, but the light was on after i changed the alt.

Turns out i didnt put the little rubber cover over the wire and it was shorting out. Check the rubber cover

 

[franklin2]

If the wire that goes to the dash light was mis-wired, the alternator would not charge at all. On the dash light I suspect a faulty regulator.

On the original question, the lights dimming at idle is normal if the load is high. Step on the throttle and everything is bright again correct? The older style alternators did not have a lot of output at lower rpms. The newer 3G are supposed to be better at lower rpms.

It could simply be your throttle body is starting to clog up, lowering the idle rpms. Have you noticed it idling a little slower lately?