Strange problem with battery light coming on. I have a 90 Accord EX. About a month ago I put a junk yard alternator on it. I had to put new brushes in the alternator.

After a week or so, the battery light started coming on. I assumed this was from a loose belt, which I tightened.

My wife, who drives the car, told me that battery light would go off when the RPM's were 1500 or higher. I asked his this morning if the same problem was occuring and she said "occassionally".

This morning I drove the car. Sure enough, the battery light came on but would go off when the RPM's were 1500 or more. However, as the car warmed up, the light would go off at lower RPM's to the point that the light stayed off at idle. By the time I had drive the car for 20 minutes the light was no longer a problem.

Any ideas? I have heard that when replacing brushes, it is sometimes necessary to take a small piece of sand paper to the stater, which I did NOT do.

 

I used to have a 90EX and had some confusing alternator indications also. Never did figure them out, but they eventually stopped.

I would suggest removing (easy in this car) alternator and taking to AZ, et al for a check out. You could have a damaged rectifier causing reduced voltage at lower speeds.

good luck

 

Put a voltmeter across the alternator's output and see what it's charging at relative to engine RPM. At idle it should be making a minimum of 13.8 volts up to 14.5 or so at high RPM. Next, use an amp clamp with a digital multimeter (you should be able to rent one at any good parts store if you don't own one?) and see what the charging amperage is.Check all cables from alternator-battery-starter to make sure there's no corrosion and all terminals and grounds are tight and clean, since dirty cables and bad connections may cause enough voltage drop due to resistance to prevent the battery from seeing the full charging output of the alternator. A complete load test of the battery is also in order to ensure that the battery is not requiring excessive amounts of charging to maintain voltage across the plates.

There is an easy way, and a cheap way, to fix this, depending on what you want to do. Easy way is to install a decent reman alternator from a parts store. Unlike a junkyard piece, you should get a no DOA warranty with it.

Cheap way is to bolt on an underdriven (smaller) alternator pulley, increasing the chargingvoltage and current by forcing the alternator to spin faster at a given engine RPM. If you do this you'll need a smaller belt unless you can tension yours enough to where it just barely deflects when you press it with your fingers.

HTH & Regards.

 

the most logical thing is to take off the alternator and have it checked, and if it is bad, get a new one. also checking battery connections and the like helps as well.

 

So... I see that I'm about thirteen yrs to the date, late for this question... but yea I might have an answer for you. I have a 90ex and I've been having the problem for about 3 months. I have a good battery and a good alternator. My alternator just won't charge. The battery light, check engine,.. hell all the lights light up when they want, like a Christmas tree. Tried everything. Found an electrician the other day and found out that I have a bad charge light. Now, from my understanding on newer model cars, all you have to do is go in the dash, replace the bulb and you're good to go. But with a 90ex, and other older models I'm assuming, the charge light is connected to a motherboard in your cluster. So you would have to get the motherboard replaced, in essence you have to get the whole cluster replaced. Sooooo I hope I could help you out.. albeit 13 YEARS TOO LATE.