Weakening alternator? :??:

[TripleBlack]

So I did a search and read several threads pertaining to alternators, but none of them seemed to touch on my specific problem. So hopefully you guys can help me... :beer:



A few weeks ago my battery gauge needle dropped from slightly passed the middle of 'normal' down to about the middle of the 'n' and the 'o'. Since I've owned my car the needle would never move while driving, and now it will go from the being on the right of the o to just about covering the n and then my oil level gauge will shoot up as will my temp gauge and my battery light will flicker once or twice.

Then my battery died about 3 days ago and thinking I had a bad battery I took it to pepboys where they load tested it but they said that the battery tested as good. They returned it to me fully charged and my car started right up. However the needle stayed in the same place between the n and o.

I got a multimeter and tested the battery while connected to the car while off. It read about 12.4 and once I turn the car on the battery was at about 14.2 or so. I let the car warm up a bit and tested it again, and it now read about 13.5.

So my question is... Could I have a problem with the alternator or perhaps a ground somewhere?

 

[Quick98Cobra]

Sounds like the alternator to me but it shouldn't be drawing 12amps when the cars off should it?!

 

[TripleBlack]

Well no, the battery read 12.4 volts while the car was off.

 

[STAMPEDE3]

Check grounds first.

 

[NVRL8TE]

Check grounds first.

This.

 

[encasedmetal]

OP_ crank the car and once running turn on the headlights so that they're shining against a wall or something similar where you can see them. shut off the car but leave lights on- if the lights get brighter then your alt is bad. if they get dimmer- it is not.

 

[SNAKEYE]

"I got a multimeter and tested the battery while connected to the car while off. It read about 12.4 and once I turn the car on the battery was at about 14.2 or so. I let the car warm up a bit and tested it again, and it now read about 13.5."

These readings sound perfectly normal to me.

Having said that, you may be experiencing an intermittant condition of a bad voltage regulator or a connection within the alternator. Technically the voltage regulator is not available sold separately from the alternator by Ford. It can be had from alternator rebuilders for about $40. Typical connection problems within the alternator are diode leads breaking off due to corrosion and vibration, and worn brushes that provide voltage to the spinning armature. Broken diode leads require that the alternator be replaced while brushes are replaceable if you can find a seller.

 

[Jonesy98]

i have an issue with mine as of late. sunday i noticed i had a broken negative cable end... so i replaced them making sure tight and secure... yesterday on the way home i noticed my gauge was actually on the "m" on normal. its always stayed there. but my battery light started flashing pretty steady on the way home (mind you its a 3 mile drive)... everywhere i have checked with my meters they seem to be fine. however my headlight "flicker" faintly while the car is running to check my charging system. every where i have researched its replace the negative cable completely... or just have my altenator rebuilt... i do however have 2 gt altenators and of course mine now is a 4 valve car. i used to rebuild altenators/starters when i was in high school, i been wondering if i can check all my parts out on my spares, and replace those good parts in side the cobra altenator being its a narrower case. again all #'s point to the voltage regulator is the same part# from what i have seen.... anyone else have some input on this also?

 

[SNAKEYE]

Headlight flickering (or pulsating) is indicative of a faulty diode set within the alternator as the alternator's output is missing 1/3 of the time.

In my case the charge indicator light was intermittent. Subsequently I discovered if I tapped the back of the voltage regulator I could cause the charge indicator light to come on or turn off. I found a replacement VR and haven't had a problem since.

Good luck with the GT alternators and swapping components to the Cobra alternator. As I understand it they (the alternators and the voltage regulators) are totally different between the two models.

 

[Jonesy98]

Headlight flickering (or pulsating) is indicative of a faulty diode set within the alternator as the alternator's output is missing 1/3 of the time.

In my case the charge indicator light was intermittent. Subsequently I discovered if I tapped the back of the voltage regulator I could cause the charge indicator light to come on or turn off. I found a replacement VR and haven't had a problem since.

Good luck with the GT alternators and swapping components to the Cobra alternator. As I understand it they (the alternators and the voltage regulators) are totally different between the two models.

yea through some research i just found out the VR's in the GT and cobra are different. even the GT's can be different also... i can buy a VR locally for $25 im wondering if its worht the effort as the shop here wants $120 to rebuild or $180 for a new reman... hmm

 

[encasedmetal]

OP- have you tried what I suggested?

 

[SNAKEYE]

yea through some research i just found out the VR's in the GT and cobra are different. even the GT's can be different also... i can buy a VR locally for $25 im wondering if its worht the effort as the shop here wants $120 to rebuild or $180 for a new reman... hmm

Not sure, but a new or reman may require swapping the old VR to the new alternator. No a good thing if the VR is having issues.

As I recall changing a Cobra's VR is almost plug and play, so the physical effort is minimal. The VR mounts to the rear of the alternator with a screw or two after plugging it into the alternator, all electrical connections are integral to the alternator.

 

[Jonesy98]

i need to really just pull mine off and recheck my wires first. i cannot remember if this was one of the sets i had to extend or change due to the 2v and 4v swap. after some further research according to advance auto both the 98gt and 98 cobras have the same part #'s on the VR's. just through trial and error, tonight since the weather is to get extremely bad and wont be driving it, i may just pull and swap both VR's and jsut see what results i may get. worst case is it just wont work at all right?

 

[mwolson]

If you find your Cobra VR is bad, send it to me and I will take it apart, and reverse engineer it if I can. I'll publish the results...

 

[SNAKEYE]

If you find your Cobra VR is bad, send it to me and I will take it apart, and reverse engineer it if I can. I'll publish the results...

????????????????????/
It's a block of epoxy!

 

[mwolson]

Dremel tool...