just found this sight and joined.hope someone on here can help me-i have a 1997 e150 conversion van 5.4 engine my problem is when i turn a/c on high my amp guage goes way down when i turn headlights on with a/c on high my guage bottoms out and wipers will go slow on high speed and dash lights flicker but the lights dont flicker outside.i have replaced the front blower motor,reostat ,and switch i just put a brand new alt. on nothing changed ,i have checked all grounds under hood all good -anybody know what the problem might be?

 

I don't know where the problem might be, but I believe I can help you find it.
Starting from the battery positive cable
Make sure the connection is clean and makes good contact.
Then follow the hot lead from the alternator and check every place it connects to anything.
Then from there one of the wires should go to a fuse panel , and there is a good possibility your vehicle's problem may reside there. Look for any kind of slight corrosion
and make sure the panel itself isn't starting to show some corrosion . There is a high resistance in the positive supply somewhere and if you are thorough you will find it.
Ford systems usually use switches to complete the ground for a circuit.
The hot feeds are at the components usually. I hope when you say you checked the grounds you loosened them and retightened them instead of just looking at them.
Let us know when you found the poor connection, OK ?

 

when i checked grounds i took them loose and wire brushed them i just pulled dash cluster out and checked the plug ins and cleaned ground wire even unplugged headlight switch still have same problem.now i am going to try to find where rear blower motor is located.

 

Don't waste your time checking all the individual components.
Check the power that supplies all those components.

 

Hanky I want to thank you for all your help,I went out early this morning unplugged the harness going to the computer everything looked good plugged it back in started van everything is working normal i went for a test drive with everything on no problem i did notice when i was loosing bolt that holds harness to computer it was loose maybee someone forgot to thighten it up when they were working on it before me.again thanks for all your help

 

Thank you for sharing the fix with us !