alternator maybe?

[cbarr300]

just looking to get some opinions.

I'm thinking my alternator is at fault here...here goes:

Anytime I'm driving and floor it the car will go good until I get to the upper rpms...then sometimes it'll just cut off on me.....the voltmeter also falls when I punch it.

When I'm driving the lights work fine...no dimming.

Now, in the mornings it cranks up fine and the alternator is putting out about 13.4 volts. Eventually it goes down to just putting out 12.4-12.8 volts though. And, after I cut it off and try to recrank it sometimes it doesn't start or just barely starts.

I checked the voltage at the back of the alternator so I'm pretty sure its not the wire going bad on me


opinions? and thanks too

 

[badstang123]

Do you have the stock pulleys on the car?

How old is the belt? Is it slipping at all?

Have you checked to make sure the nut holding the pulley on the alternator is tight?

Let' start with those simple fixes and then move on to more expensive and complicated possiblities like replacing the entire alternator. Or you can just pull it out and have it bench tested somewhere. Most places won't charge you.

 

[badstang123]

I'd also pull the battery and have it load tested. Just so you can start eliminating possiblities.

 

[1TallMF]

I agree, have both items bench tested and go from there. I believe advance also does in-car charging system checks, they have this hand-held device that just hooks up to your battery, and it performs dynamic checks as the car is running. And its free. Only thing is, if the problem only occurs at high rpm's, this test won't catch it as it only simulates running around 2k rpm.
Also, clean all of the wire contacts on the alternator, and your battery terminals. You might also check the charge wire going from the alternator to the junction box (beside the fuse box) by pulling-off the wire cover and seeing if there are any vulcanized spots or burnt areas. If all checks-out, my vote is that your alternator is taking a dump.

 

[blksn955.o]

It also could be some kind of wire heat soak or age. Maybe test the poss. and neg. batt. wires along with grounds. It seems that with the age of our cars and frequent elec. issues the grounds/wires are just getting old.

 

[HISSIN50]

FWIW, when you start the car in the morning, you should see 14.4 volts +.

I like the dynamic testing idea that 1TMF mentioned. In a situation like this, a bench test doesnt always catch the issue because the alternator or battery hasnt completely crapped its pants yet.

FWIW, when you see anything less than ~12.6 volts, you're discharging the battery.

Good luck.

 

[cbarr300]

thanks for the replies guys. belts not slipping and the pulley is good. I'm going to go over the grounds tommorow morning and refresh those. It does seem like it's a heat soak issue. It's perfect when I first crank it up...but once the car gets hot it just starts going south.

I'm going up to pep boys tomorrow to have them test it out if I can't get any better with re-doing my grounds. Spending around 130 for a part that isn't bad isn't exactly fun.

I hooked my dmm to the back of the alternator so that should eliminate wires from being the problem, right? or am I missing something there?

thanks for the help guys

 

[cbarr300]

welp, I got one of my friend's alternators and replaced mine with it and that didn't fix nething.

still doing the same thing....it was at about 13.6 when I cranked it and was good til I started driving it...then it dropped down to less than 11 and eventually the batt. died. It's not the battery as that is new and is charged good. The battery wires are good.

still haven't checked grounds..that's the only thing I could think of.

any suggestions?

 

[cbarr300]

well, quick update just to go down in forum records...

I put a ground to the ground test screw and the voltage went up to 14.3...soo...found the problem.

I started messing around with the voltage regulator (I'm pretty sure that's what it is) harness. I pushed it down and the charge started going up soooo..I guess it's time for a new harness.

I decided to check this due to a thread I read where hissin talked about the harness soo...big thanks to you and everyone else on this thread...saved me 130 bux

 

[cbarr300]

whoops, double post

 

[HISSIN50]

For a quick test of grounds, toss a jumper cable from the negative battery terminal to the frame rail. This will accomplish the same thing that the chassis ground.

As far as other reasons for the issue: I might peel back the alternator wiring sheath at the alternator side and make sure the wires are not vulcanized.

It really does sound like there's a bad cell in the battery or something else at work though. Also, are you reading 13.6 volts at the battery or at the alternator? Make sure both read within 0.50 volts of eachother (that's the outer tolerance for voltage drop). You might be reading this at the alternator but there's an alternator power cable issue keeping the current from reaching the battery.

Random thoughts. Good luck.

 

[HISSIN50]

You posted all that after I loaded the page but I was typing a long one on another thread.

Glad to hear you got it whipped. I also replaced the harness (Fordfuelinjection sells a nice robust replacement harness. I just got one from LRS though).

Good luck.

 

[cbarr300]

lol, yeah, real glad i got that one whipped...tired of charging my battery every morning to make it to work lol...then carrying around a spare with me just in case.....twas a hassle

thanks again

 

[cbarr300]

welp, just one final follow-up. One of the wires broke off inside the insulation right by the plug. I have a 93 f150 with the 4.9L straight six that I don't drive anymore since the cobra's running well enough to get me places. I ended up cutting the wiring harness off that one and attaching it to the wires on the mustang and all is good. Charging at 14.46 when I first crank it and eventually going down to the high 13s.

None of the parts stores around here had the connectors so I figured this works for now. I have it ghetto-rigged on the truck just in case I have to take it one day.

 

[HISSIN50]

Sounds good.

FWIW, if you get lucky you can sometimes find a regulator plug in the wiring aisle of the parts stores - it's hit or miss (in case you need the truck ASAP and this set-up is iffy).

Ooooh, if my memory is correct, Pep Boys has the reg plug. Might be worth a phone call.

Nice work getting it fixed.

 

[cbarr300]

yeah, that was the first place I looked was pep-boys lol...I swear u could build a car in that place.

autozone had one..but it was for a 2g altenator even though it was under the 3g section.

I got them to order one for me so I'm gonna put that on the truck when it comes in.

but yeah, I helped someone jumpstart their explorer and happened to notice the alternator plug on that car and said..."Hmmmm...."


oh yeah, now I have problems with the coil.....Either I have a bad connection or it's going out on me. My car wouldn't start..and when it would it would die right away. I ended up hitting it around with a wrench and the car started perfectly.

money pit but I love it when it works. It's like a new car every week lol

 

[HISSIN50]

A 2G regulator plug is the same as a 3G plug as I recall.

A lot of folks have had good luck with AZ's 14 dollar coil. If I didnt have an MSD (I got a real good deal on it), it's the one I'd get.

Just make sure that you have a pulsed ground going into the coil (put a test light across the two wires going into the coil and look for the light to flash real fast). Otherwise, it could be an ignition issue downstream (the TFI is the next item down the river from the coil).

Good luck.

 

[cbarr300]

hmm...guess it wasn't a 2g plug then. It was a lil wider than the one I needed. I'm pretty sure its the coil. I messed around with the wire and hit it and it started going good again. Looks like I'm goin to AZ...14 bux..might as well.

U think it would hold up to the msd box?