alternator/ underdrive pulley question

[montyd]

so my car has a rather large set of under drive pulleys on it. so big that at night at a light the alt guage drops to 12v and even lower if i sit for very long, and if an unsespecting mustang pulls up next to me and i stand on it the volt guage drops to 10 volts. i have the stock pulleys(i think) and am planning on putting them back on this weekend. my question is, the guy that i got the car from said he was planning on putting an alternator from a cop car on it since it is 200 amp to make up for it. is that a possibility? other wise if i put the stock pulleys back in do ineed to have the car re tuned?
thanks in advance
dan

[fastblackmerc]

so my car has a rather large set of under drive pulleys on it. so big that at night at a light the alt guage drops to 12v and even lower if i sit for very long, and if an unsespecting mustang pulls up next to me and i stand on it the volt guage drops to 10 volts. i have the stock pulleys(i think) and am planning on putting them back on this weekend. my question is, the guy that i got the car from said he was planning on putting an alternator from a cop car on it since it is 200 amp to make up for it. is that a possibility? other wise if i put the stock pulleys back in do ineed to have the car re tuned?
thanks in advance
dan

All you need to do is raise the idle by about 200 RPMs. You will need a tuner to do this.

[montyd]

ok, what about at 5800 rpm when the alt guage is at 10 volts? seems like the car wouldnt be making enough voltage to power the coils and everything else that it needs to make good power

[clmrt]

Freewheeling alternator pulley in our cars at WOT. Go WOT, volts drop, and three seconds later the voltage will return as the pulley clutch re-engages. Works like a clock in my car, same thing every time.

[fastblackmerc]

ok, what about at 5800 rpm when the alt guage is at 10 volts? seems like the car wouldnt be making enough voltage to power the coils and everything else that it needs to make good power

Can you post a picture of the underdrive pulleys?

How old is the battery?

I'd take the car to a FLAPS or Sears and have them check the battery & charging system.

[montyd]

at night its a bigger problem because the headlights dim to almost nothing above 4000 rpm.

[montyd]

ill try and get pics tomorrow, battery appears new, but hard to tell. ill grab the teaster at work tomorrow and check the system. ive known the p o of the car for years and it did this even right when he put them on. drives me nuts

[Rockettman]

Best place to start (IMO), is to go back to all the orignal pulleys; and see where you sit then.
That may point out a problem with the charging system.
If all is fine then; put the "underdrives" back on, and start going with the suggestions above from the other members.
(Always easier to track a problem with stock pieces FIRST).

[montyd]

i put our testing machine(i work for a body shop/ mechanic shop) on the battery and tested it. the battery is fine, and the charging system at idle tested out fine to. at idle 14.29 volts from the alternator. i guess ill be putting the stock pulleys back on to fix the problem. i hope the same belt fits with the stock pulleys on my mustang (fox body) the belts are way different

[montyd]

oh, and i watch the volt guage as i stepped on it this morning and the volts dropped to ten and it took close to 10 seconds for it to come back up. duno if that matters or not.

[fastblackmerc]

oh, and i watch the volt guage as i stepped on it this morning and the volts dropped to ten and it took close to 10 seconds for it to come back up. duno if that matters or not.

Still don't think the underdrives would cause that.

I still say it's the alternator.

[Rockettman]

oh, and i watch the volt guage as i stepped on it this morning and the volts dropped to ten and it took close to 10 seconds for it to come back up. duno if that matters or not.

Actually yes it does.
As Jim says; pulleys wouldn't do that. Pulleys will drop voltage until you start to accelerate. (The opposite of what you have).

(I'm just thinking out loud here...) maybe there could be a problem with not only the regulator in the unit; but also internally (brushes, windes, and such). It seems that as the rpms go up - the unit spins faster and faster / gets hotter and hotter internally - and may be "giving up" as that happens. More than likely it sounds as if the regualtor is just faulty.
This could explain the proper reading on your tester at idle.
Try another alternator. NOTE: get it bench tested BEFORE YOU LEAVE THE STORE. Countless people will tell stories of getting home only to realize the replacement is bad also.

[montyd]

ok ill try that and see once i get the money for it. thanks!

[Rockettman]

^^^ People on here are pretty awesome! Contact a local member, and see if they'd take theirs out for you to try. At least you'd know then.
(Just a thought).

[fastblackmerc]

Actually yes it does.
As Jim says; pulleys wouldn't do that. Pulleys will drop voltage until you start to accelerate. (The opposite of what you have).

(I'm just thinking out loud here...) maybe there could be a problem with not only the regulator in the unit; but also internally (brushes, windes, and such). It seems that as the rpms go up - the unit spins faster and faster / gets hotter and hotter internally - and may be "giving up" as that happens. More than likely it sounds as if the regualtor is just faulty.
This could explain the proper reading on your tester at idle.
Try another alternator. NOTE: get it bench tested BEFORE YOU LEAVE THE STORE. Countless people will tell stories of getting home only to realize the replacement is bad also.

Make sure you get the right alternator. They might try to sell you one for a CV or GM. They will not work. I believe our is a "4G" style. You need to get one like this:

http://www.dbelectrical.com/p-4111-new-mercury-marauder-alternator-46l-2003-2004-8314.aspx

[JBFTech]

If you still have the clutch pulley on your alternator, you might want to check that too. I've seen quite a few on cop cars slip intermittently, varying RPMs and for various lengths of time, and if it starts slipping, you're not charging. Only drawback to the clutch pulley is the price, they aren't cheap (through Ford) but are great at eliminating belt chirp on WOT hard shifts!


Sent from my SR-71 using Tapatalk

[montyd]

does anyone rebuild alternators these days? i checked my cost through napa on a marauder specific alternator and it was almost 300 bucks.....

[montyd]

i now see the one on the link is 140 lol thanks guys! your the best! Can i change to a non clutch type alternator? or does it matter?

[montyd]

would it be the same as the 01 cobra alternator? in other words wi=ould this one work?
http://www.ebay.com/itm/FORD-Mustang-Cobra-NEW-ALTERNATOR-97-98-99-2000-200AMP-/170914615044#vi-content

sorry about all the questions, still new to these cars

[Rockettman]

^^^ the ad says it's not the same (as per their "pull-down menus"); but give a local Ford Parts counter a call, and see if the numbers match up.

[bugsyc]

Very nice.The link for the alternator in post 15 looks like it has the pulley for the eaton on it...SC6

[montyd]

i went through db electric and bought a stock replacement. i wanted a better one but dont have the cash at the moment. (my marauder is my 4th car, maintaining a fleet gets expensive :eek: )