I tried to post this last night, but I can’t find it. Sorry if it appears to be a double post.
I have a '97 Taurus SHO with the DOHC V-8 engine. I have had several SHOs, and parted out one after a camshaft sprocket failure at 203K miles. I bought this SHO a couple of weeks ago at an auction. No guarantees. It did not have the alternator light on when I drove it home. I drove it a little while later, and it ran worse and worse as I drove, so I headed back home. It literally died in the driveway, and would not crank. I recharged the battery overnight, and it ran perfectly until the battery ran back down. Another battery charge and hooking it up to a machine at Autozone revealed that there was no charge. The charge light never did come on. I had another SHO alternator with a "rebuilt " sticker. I had the AZ guys test it, and it was good. I installed it. Still no charge, but now the charge light is on. Hmmmm… what’s going on here? Is there a fusible link in that circuit somewhere that I don’t know about? Any other ideas?
What I would want to know right now is whether or not the alternator itself is actually putting out any power. The simple, quick look is to run the car & put a multimeter on the battery to read voltage. Then check voltage directly at the alternator. The alternator should put out something close to the 14-15V range & should read similarly at the battery terminals. If you have good voltage at the alternator but not at the battery, and you know that the battery will take full charge (at least 12.7V or so) then you know that the problem lies with the wiring in between.
I know this isn’t proper etiquette…however…start the car and pull the positive batt terminal…In more complex vehicles you can harm some sensitive electronics in the car…but not in yours…If when you pull the pos terminal cable…and it dies immediately…the alt isnt putting out power.
You need to check your alternator to see if she is getting 12V HOT all the time running TO IT…if not…she no worky…and wont charge your system via that same wire…
As usual Cigroller is right on point…(I’m getting tired of saying this…hey Cigroller why dont you post a bunch of bunk one time or another so I can say…“CIGROLLER IS WRONG…DEAD WRONG!”). Check your resting and running voltage…read above…he’s right.
However if you don’t have 12V Hot all the time at the alternator then it has no shot at getting any generated voltage back into the battery… CHECK THIS FIRST…
AND DO NOT IGNORE YOUR GROUNDS…batt connections clean and tight also? The Ground is as important as the HOT…many people don’t seem to get that…Not saying you…but many dont give that ground enough credit…Nothing but nothing works without it…
DO NOT DISCONNECT THE BATTERY WHILE THE ENGINE IS RUNNING! This can cause a voltage spike which can damage computers and modules. And your vehicle has plenty of them.
LOL…Yeah yeah…every time I say that…I get the following response. I KNOW…I know…its true and you are correct. Its just that I have done this on so many vehicles for so many years and nothing has ever happened…Perhaps I am just lucky, but I cant be THAT lucky. I can say that the vehicles were all older than say…2002?
I cannot argue the point however because I agree with Tester.
Hey Tester…I am trying to think if there is any other safeguard in place inside the alternator that would not permit any massive damage…I mean the regulator is there and hopefully working… I would think that is all that is needed… When your voltage regulator blows and the alternator is pumping out say 19.5…you start blowing light bulbs… But Why have I never seen ECU’s get fry’ed? I mean THEY SHOULD FRY… But I never see this…even when the regulator goes… I DO wonder what else could possibly be saving these devices… I cant come up with much. I;ve seen an alternator pump out 26.4V before and still nothing but the headlights burned out…I have ALWAYS wondered WHY…Why not so much more damage… The fuses? sure could be… I mean everything important is fused…
Listen to Tester…as I cannot refute his statement…HE IS CORRECT!!! Cant argue…
But please do however check the resting voltage…running voltage and make sure the alt has 12V HOT ALL THE TIME… DISREGARD my pulling the pos cable test… I know, I know…
Have you tried checking to see if you have a charge light before starting the engine? Just turn the key until your dash icons light up. You should see a charge light illuminated. If not then your alternator will not start charging the battery. The charge light provides the current necessary for the alternator to work properly.
I should have posted back earlier. There was no apparent output from the “new” alternator with a sophisticated tester. The no charge light was on with just the key and after the car was started. It turned out to be a loose connection at the under-hood fuse block where the large wire to the alternator connected to the 175 amp master fuse. Strangely enough, the fuse didn’t blow. The loose connection caused a lot of heat in that area that melted the some of the plastic covering the loose nut and bolt. Another nut and bolt were used to hold the connections to either end of the big fuse, which I also replaced, after I cleaned them up. All’s well.