Noticed charge indicator light came on and voltage was dropping fast while running - diagnosed at NAPA as bad battery - replaced battery.

Next day - same thing - diagnosed at different NAPA as bad alternator - replaced both alternator and battery (to make sure it wasn't a bad new battery).

Next day noticed charge indicator light would come on and only stay on when above idle - would go off when at idle.

Next day - charge indicator light is now staying on (under all conditions) and voltage is slowly dropping from normal and I'm expecting it to eventually die again. Have had re-diagnosed and charging systems checks out okay - but light still on and voltage (while running) still dropping!

What now? Both the battery and alternator are new?

 

How are the condition of your battery cables? Any open circuits? Damaged connectors?

 

verify your alternator connection. They put Di-electric grease in the plug on the alternator and it prevents a good solid connection. If you push in in your connections it should solve your problem. When you plug in the plug it will actually push out the wires..... push them back into position into th plug. I had the same problem. I killed 2 batteries within 10 miles. 5 miles to the parts house and then 5 miles home. Both were drained dead! I put my charger on the battery and started checking everything.... It turned out to be the connection at the alternator.

 

All connections appear good and solid and corrosion free. Also it only drains power when running (more load than is being restored/maintained by the alternator). No real drain when sitting overnight. I'm going to try to have the draw checked at both ends of the alternator cable tomorrow. Although the last check showed the alternator power getting to the battery at idle and under load!

 

I am having the same problem, replaced the alternator, batteries and cables it has not fixed the problem. The truck runs fine untill the batteries get low then it will not fire back up. I have tried everything did you fix your problem?
Thank you

 

This may not apply to your situation, but may help others with 97 Expeditions.
Apparently there are 2 different alternators for 97's. One for trucks built pre 6/28 and one for after 6/28. Most auto suppliers only list one on their computer and insist it is probably just a model # change - I don't think so! I have found so far that NAPA and the Ford dealer are the only ones that list and stock 2 different alternators (akthough externally they look identical). Neither could tell me the difference between the 2 and neither could Motorcraft. I have since installed the factory OEM replacement for pre 6/28 97 Expeditions (was given a post 6/28 alternator the 1st time) and have had no problems since!

Good Luck

 

Story:
I had a '98 Chevy Monte Carlo that I changed two alternators and a battery on (in 1 week), used the same methods of problem solving that you did......yup, the mfn had changed the alternators and the auto parts stores weren't up on the info about the change.

The dealership said the alternator sends a "signal to the computer"....and that is where the problems was, vs. a regular alternator.

Oh, and while on the subject........they replaced the computer (under warranty).

Don't know if that helps to explain it.

Aloha, Mark

 

Hi,
I know this may sound crazy cause it did to me....I have a 99 exp eb 5.4 that had the same problem. Changed all the same stuff. Under the hood up near the firewall there is a fusebox (drivers side). There is a fuse...I think a 20 amp... that your owner manual will show that says ... alt field... Mine was blown. I was told to check it and I did with a test light...it checked good. I pulled it out and looked at it and it even looked good to the naked eye. But you could see a fine hairline crack in the side with a magnifying glass. Anyway changed a .50 cent fuse and fixed the problem. Hope this helps. Hey I didn't think it could be that simple either...try it!! Good Luck!

 

I checked the battery, replaced the battery, replaced the alternator, and by accident touched the fuse box under the hood on the drivers side... I noted a slight change in RPM... The Battery light was out... jiggled the box... The battery light was on... The fuse was not blown, however it did have a hairline crack... That cost me money and about 4 hours of reading, and testing etc...

 

I had the same problem. I replaced the fusable link from the starter to the silinoid and fixed it...try that!

 

we have a 97 eb. We had a simaler problem with the charging system, no alternator output. changed the alternator and problemwas solved (I thought). Problem happened again and alternator checked bad replaced it again problem went away again. A week later problem was back changed battery becouse had to go 60 miles home. Did some checkes on harness and found that the signal wire from the ignition switch had no voltage. After much wire wiggling and fuse checking with ohm meter voltage returned. so far so good but will check for crack in fuse. Rule one in troubleshooting check the easiest thing first