1993 940 Alternator - Guess it's my time?
 

Off to work, first stop sign ABS light came on, progressively worse as ABS and Service light came on every stop. Then even worse, radio stasted to flicker.
Got to work battery dead. Bought a new one and made it 50 miles to home.
Dashlights all on, A/C does not work (104 degrees out!).

When I got home, new battery dead.
Tried to restart, once, started, twice, no go.

Charged it up for 20 minutes.
Started, all lights on dash on, radio flickin' on and off, hit the haedlights and it just died.
Tried again, dead.

O.K. all good, new alternator coming.
My question is this; will the idiot lights go out when I replace the alternator?
And more important, will the A/C start working again?

Give it up...

It might be too late to act on this but lots of times the alternator will stop charging when the brushes are too worn .. they can be replaced by themselves for a lot less $.

http://www.fcpgroton.com/product-exe...ategory_id/111

Well I had the alt tested, dead as can be so it's being rebuilt ($95), so I figure good enuff but thanks.

Big question is, I haven't read anything about the A/C going down during these scenarios. My A/C was working fine until the discharge started.

Guess I'll find out soon enuff.

last dieing gasp
 

As the battery voltage dropped, and the components that required high amperage draw failed one by one the trusty ignition still sparked away allowing the engine to run. The compressor clutch requires several amps to engage and operate the compressor not to mention a minimum voltage of say maybe 9 volts to remain engaged. On a carbeurated engine with a mechanical fuel pump the battery will keep the engine running for quite some time.headlights draw so much from the battery that the fuel pump relays beacame unlatched and no longer powered the pumps.I pronounce your air conditioning to be fine. when you get the new alternator installed depending on the age of your current battery, you may want to change out the battery as well. A good way to test if your alternator is working is to remove the positive cable from the battery momentarily and see if the engine continues to run...if it quits then the alternator is not putting any voltage out to allow ignition to work.

It is generally recommended to not disconnect the battery while the engine is running.

You were good up to this point. Taking the battery out of the circuit while the engine's running could easily blow the diodes in the alt not to mention cause a fat arc at the battery possibly exploding the battery. If you're going to do this, recommend wearing face shield and flak jacket... :eek:

To see if the alternator is working, just use a volt meter across the battery; should be about 14-16V with the engine just above idle.

Happy Ending
 

Well boys, all good to go.
The alternator shop said regulator and rotor where shot.
Dropped the rebuilt in and everything is back to normal.
A/C works like a charm, all the lights are off on the dash, even the airbag and engine light I had taped over...

http://www.rapiddog.net/happyboy1107847043.gif

I never promised good advice, just past experience. ..so whats the difference from turning off the key versus removing the battery from the charging circuit? why would I blow a diode which is there to rectify the circuit (change ac to DC) I can see if you were careless and caused a large spark you might ignite any gases from the battery that had accumulated in the vicinity.....awww come one most batteries are sealed nowadays anyway...ok so kids dont try this at home...:)

Not to belabor the point but since you asked...

Modern maintenance free batteries are not technically sealed; ck this link for more details; esp. the "Exploding batteries" section.

Turning off the key is nothing like (electrically) disconnecting the battery while the engine is running! While the end result may be the same (engine dies) the latter causes extreme electrical stress to various components within the vehicle!

Certain electrical components, like the battery and alternator, are hard wired into the auto electrical system, that is, they are not switched in/out with relays (regardless of key position).

When you turn off the key, you are turning off the ignition system, causing the engine to stop running, causing the alternator to stop turning, causing the charging system to cease charging; i.e. current stops flowing from the alt to the battery.

Conversely when you disconnect the battery with the engine running, the alt is still producing current for the battery (we're talking serious current here too) so if you suddenly take the alternator's load (the battery) out of the circuit, the alt will generate a sudden voltage spike which can overload the diode pack and/or other electronic components (e.g. control units) in the system. That's why you don't want to disconnect battery cables while the engine is running.

When your right your right...sometimes its still 1966 in my brain.