1990 Mustang 2.3 Charging Problems

JKDZ28 · Jan 21, 2009

Hey guys, we have a 1990 Mustang 2.3L with some issues that have not been resolved. We have been working on it for months now and cannot completely solve the problems. I figured I would ask you guys because you all seem to know your stuff.

Problem: The mustang will not hold a battery charge. After replacing an array of parts, the problem still remains. We can hook a volt meter to the car and it shows that there is a power drain somewhere. After a quick drive the battery will only read 11.4 volts. We have a 1987 Thunderbird Turbo Coupe that we have borrowed the alternator from and the issue still remains. When driving the car, you can flip on the headlights and the volt gauge inside the car drops dramatically. To make sure the alternator is working correctly, we can disconnect the battery with the car running and the alternator keeps the car running even without the battery connected. This leads me to believe the alternator is fine.

New Parts:

Battery (2 times)
Battery cables
Starter
Diode Suppressor

We have had the alternator checked out by a show (removed from car) and it tests good. The tests comes back that the alternator is putting out 67 amps.

If anyone can help us out we would be very greatful!

Jared

redstang80 · Jan 21, 2009

Hello,

First of all, I would suggest not trying to disconnect the battery while the car is running, you can ruin your alternator.

I've had similar problems on my '80 mustang. Some things to check:

1. make sure your grounds are tight
2. make sure the alternator is connected up correctly--if its not hooked up right, it could ruin the alternator.
3. hook the battery up to a charger, charge it fully, try to start the car, then hook the battery up to the charger to see what the charge is on it. If there is a significant drop in the battery charge, I would take it to a automotive parts store to be checked--it might need replaced.
4. Have a automotive parts store test the alternator and battery to see if they are working correctly.
6. Run the car for awhile, or very frequently. When a new battery or alternator is installed, the alternator needs to be "charged." When the car is run for awhile, it is able to charge the alternator.

Hopefully these help

dreamer1uk · Jan 28, 2009

Hi,

The stock Alternator puts out around 80amps. Your alternator needs to be within 10% of that number.

Did you hook up a Volt Meter to the Battery when the car is running? It should read over 14 volts. Belt tension and bad grounds will effect the charging system too.

Its sounds to me like the Alternator Voltage Regulator is bad but again, id have it tested to make sure.

89lx2.3 · Jan 30, 2009

Check the Alt, and batt at a shop. (Most of the chain stores will do it for free). It is easy, when fooling with these things trying to work out a problem, to end up frying one or both of them. On your car the regulator should be built into the alternator, but might be servicable seperately.

"To make sure the alternator is working correctly, we can disconnect the battery with the car running and the alternator keeps the car running even without the battery connected." - this could have damaged your alternator already.

erob914 · Jan 31, 2009

power drain

To find the power drain do the following:

-remove negative battery terminal.
-hook voltmeter or test light in series with unhooked bat. terminal and neg battery post.
- If there is a drain voltmeter will show voltage or testlight will light.
-Start pulling fuses one by one.
-When meter drops or light goes out you have found the circuit the draw is on.
-Consult wiring diagram to find which circuits are on that fuse.
-Use your noggin to track the offending component.

* There will be some voltage draw at all times for the computer, radio, clocks, etc... This should be at most 1/2 volt if not smaller. It will be enough to make the test light light very dim but not go out.

mountain · Feb 9, 2009

I have a 1997 mustang Gt, convertible. Has been with me since 1998. All of a sudden the battery is dead if it sits for 24 hours or more. We have changed the battery twice, it has been tested by mechanics to see what the draw is, no answer. Can you help.

1990 Mustang 2.3 Charging Problems

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