Power Problems

[Arob27ss]

I have a 1990 5.0 and currently out of ideas of what’s wrong. Put in a 130amp alternator in March and every time I turn the headlights on I can’t go above 2k rpms and about 55mph anywhere. It has electric fans with a digital control and when that kicks on with the headlights on its bogged down. So I took it in and the Mechanic said the alternator had a diode ripple so he warranties it out and got me a 200 amp one and replaced 4 ground wires with it and still Boggs down when the fans kick on. All the wiring is the right size and can’t find anything else wrong with it. It’s pulling 14.1 volts when fans kick on so there should be no issue on that end but don’t have a clue what else to do. Any help would awesome

 

[broncojunkie]

Are you sure your grounds are good? There should be a good, solid ground between the negative battery post, chassis, and engine block. Also, sometimes these cables look good on the outside but have corrosion throughout the copper wire inside.

I would also consider pulling the new alternator and having it bench tested. Unfortunately, it's not easy finding good electrical parts these days. The quality control is pretty much non-existent. Just because it's putting out 14 volts doesn't mean it's making enough amps.

 

[Arob27ss]

Yes they changed out all my grounds and they even tested this new alternator as well and all good there, that’s the problem they are at impasse because everything looks and is hooked up properly and they can’t find anything that is wrong, everything runs great until the electric fans kick on then the bog down happens. It was originally taken in for the power issues and that’s when they found the “New” 130 amp alternator was bad so they tested it on a 200 amp and everything seemed to work fine so they got one of those and put it in and still doesn’t run 100 percent. Not sure what else to do honestly.

 

[broncojunkie]

What size fuse or breaker do you have wired into the fan? Curious if maybe it's pulling major amps due to a problem of some sort. If so, it should trip your fuse/breaker in that scenario...unless the rating is really high.

 

[Arob27ss]

Not sure I’ll have to check it whenever I get the car back. Mechanic has had it since June 13th.

 

[tycosp23]

What grounds Exactly did he change? Engine to body, Battery To Body etc. Are they all ground down at the location for bare metal to bare metal. if so the next thing you may want to try is soldering the grounds to the body. With a problem like that is shows a bottle neck. With DC what gos out comes back so there is a ground or a power supply management. Don't over look the starter relay as well since those have a tendency to not function correctly.