my sis had this problem with her vw golf, it was the alarm and never driving solved by a solar trickle charge that sits on dash which charges the system and the solar panel worked in scotland!!!

 

It could be the voltage regulator. Oh BTW Calixtus Your car should charge, no matter how long or short you drive it. Just sitting there idling will charge up a battery.

 

And that would be why I probably need a new alternator...

 

Oh well, looks like you've already bought a lot of parts, but for future reference and possibly to help someone else out, here are some simple tests you can do to check your charging system.

First, as has been said many times here, buy a good quality multimeter, something that can measure volts, resistance, continuity, amps, maybe a few other things. If you want to own and drive an old car around and fix it yourself when something breaks, this is one tool you have to have.

Very first thing is to check the volts on the battery itself while the car is shut off. Just set your multimeter to measure volts in the appropriate range (some meters don't require you to do this, but some have range settings i.e. 0-10 volts, 0-50 volts, etc).

Check the voltage across the battery posts before you start the car. If the battery has been happily charging and is in good shape you should see around 12.7 - 12.8 volts. Something like 12.1-12.2 is way low and something ain't right.

Second step is to start the car and then check voltage again across the battery posts. Be mindful of the fan especially if you have no fan shroud -- it's very easy to get caught up in what you are doing and stop paying attention to how close you are to the fan. At a fast idle you should be seeing in the neighborhood of 13.5-14.5 volts (ballpark number is 1.5 + whatever your initial charge was with the car not running).

If you aren't seeing something like 14 volts with the car running, shut the car off and set up a voltage regulator bypass test. To do this you disconnect the connector to the regulator (it will have the "I A S F" markings). Set up a jumper wire across the "A" and "F" terminals of the connector as shown in the picture. (This pic by the way is taken from James E. Duffy's book "Modern Automotive Technology" -- somewhat pricey but an absolute wealth of info and great for anyone just starting out, or even to remind experienced people of a trick or two they may have forgotten).

With the jumper in place, start the car and again check voltage across the battery. You should now be seeing full alternator output at the battery, around 14.5 volts. If this is the case, then the problem is the regulator. I think around 10 bucks for an electronic one at your local parts store, more like 40(?) if you need a concours-correct one.

If you are not seeing full alternator output after bypassing the regulator, well then you are looking at either the alternator or the alt wiring harness. At this point I've exhausted my (limited) bag of tricks since the regulator was the problem in both the 72 rustang and the 68 cougar. The voltage regulator seems to be almost a standard maintenance replacement item on these cars.



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thanks for the help...the battery is at 97% now...ill give it a couple of days to see if it stays charged

 

thanks rustang, that helps me a lot. I have a multimeter but I didn't know how to isolate the trouble. I'll give it a look.

 

atleast its not a hummer h2 LOL the battery dies if it sits 3-4 days without use cause the computer drains power all the time everyone i know that has one gets alot of deat batteries cause they have other vehicles they use during the week

 

Dead batteries suck but if you have enough money to buy a H2 and not drive i think you could afford a battery or two...no offense

 

If you are dumb enough to have a hummer then you deserve it, give me a defender 90/110 or landcruiser anyday

 

probably just the factory side post battery they use gm has a ton of trouble out of them(side post literally fall out of them)