Slow start

[BoomOP944]

Hey guys, my 86 944 N/A is really slow to start lately. When the car is running and I pop the head lights up, you can see the battery needle dip down....same thing when I go from high to low beam. I turned the car off and realized I left the window down. I popped the key in and hit the switch and watched the battery voltage deplete in front of my eyes.
I can drive for about 20 minutes or so cut the car off and 10 minutes later again, turn the key and my voltage is barely above the red and it takes awhile to start.

Is my alternator not charging, or is my battery just shot and needs replacing?

Thanks guys,
Bob

[John_AZ]

Clean all the thick battery cables and ends CLEAN. Both sides. Be careful and cover the TDC hole on the bell housing when you take the NEG ground off to clean.

Take the battery to a shop and have them check and if good---recharge the battery out of the car.

If the battery is good, put it back in the car and check for a drain on the battery per Clarks.

Have the door shut or you will get an incorrect reading with the interior lights on and door buzzer active. My discharge rate is 10-12ma. Clarks says up to 65ma is OK but that is HIGH.

Excessive Battery Discharge Rate

If you find your discharge rate is normal, remove your VR (voltage regulator) and check to see if the carbon feet are equal in length. Under 7-8mm is too short. If one is a lot shorter than the other, replace the VR. You should polish/lathe the alternator slip ring to aviod having the slip ring chew up the new VR carbon feet.

If your battery is still not being charged, take the alternator to a shop and have it tested.

You can save time by taking the battery and the alternator to a shop at the same time.

In the states, most auto part stores will do this for free. Not sure about the UK.

MORE, sure:
Alternator & Charging System Checks (Alternator Testing)

GL
John

[John_AZ]

Do not "jump" the car battery with another vehicle or quick charger.
You may distroy your DME computer