|
|
|
|
| Author |
|
|
Architecture & Porsche's
Join Date: Jan 2006
Location: Austin, Texas
Posts: 3,189
|
'81 928 battery/alt "blinking" attention light on dash...
Ok, my '81 is miffing me a little.
Put a new battery in it 3 weeks ago. Yesterday, get the continuously blinking attention light on my pod, but no subbordinate light to indicate why the light was blinking continuously. Under the hood, nothing odd, all belts are there, good oil pressure, etc. I drive it home & back to work, it wont restart: as if the battery was dying. I suspect the alternator, & have it pulled & tested, test came back good. Thoughts?????
__________________
Porsche Club Racing National Scrutineer '89 Andial 951 '82 928R '74 911 RSR 3.6 |
||
03-13-2008, 10:48 AM
|
|
|
Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
|
Just the usual, recheck everything related to the most recent repair.
Why did the old battery come out? Buried old alarm system? |
||
|
03-13-2008, 12:10 PM
|
|
|
Architecture & Porsche's
Join Date: Jan 2006
Location: Austin, Texas
Posts: 3,189
|
Old battery developed bad cell from discharging too many times. The car has been gutted for 1.5 years now, this has never happened before.
The auto place who pulled the alternator says it's bad, the alternator re-build place says it's good, so the alt. guy recommended checking the small wire to the bottom of the rectifier??? Anyway, the alt is back over at the auto place & they're following the advice of the alt. rebuilder....we'll see.
__________________
Porsche Club Racing National Scrutineer '89 Andial 951 '82 928R '74 911 RSR 3.6 |
||
|
03-13-2008, 12:18 PM
|
|
|
928-Electrics Guy
Join Date: Jun 2007
Location: Phoenix AZ
Posts: 715
|
test the small wire that goes to the alternator - disconnect it and see what voltage is on it with the ignition off (should be 0v) and with the ignition on (should be 12v). Connect it to ground and see that the charging light on the dashboard comes on. If these check out OK it is highly likely that this circuit is working correctly.
One additional test is (with the small wire still disconnected)connect your ohmmeter to battery +ve (jump post) - turn the ignition on - measure resistance to the small wire - what do you get? - it should probably be in the range of 10-20 ohms under these conditions. Alan
__________________
1994 928 GTS Black/Black Manual Last edited by Alan in AZ; 03-13-2008 at 05:32 PM.. |
||
|
03-13-2008, 04:31 PM
|
|
|
Registered
Join Date: Apr 2007
Location: LA County
Posts: 53
|
Alan, any way to confirm this...
Mark, I've had a similar aggravation on my 78 for about nine months. Even though just over 13 volts shows on a multimeter across the battery terminals with the engine at idle, my dash alternator light is sometimes on, sometimes off, and the volt gauge is sometimes just above 8, sometimes up to about 10, and never steady above 12. Sometimes, a high rev will turn off the light, sometime hitting a bump will do it.
I cleaned the ground points and clipped/re-crimped the alternator wires, but that didn't make a difference. I'm hoping it's a problem in the dash; oddly, my low-oil light (in the same dial) is doing the same on/off thing, with oil topped up. Alan, is there any way to confirm that problems like these are solely in the dash? (I used to have a similar, jittery water-temp gauge problem that I wrote off as a short, until my thermostat seized up one day and blew up my radiator, so I'm a bit more concerned with the blinking light thing than other posters might advise.) |
||
|
03-19-2008, 10:50 AM
|
|
|
928-Electrics Guy
Join Date: Jun 2007
Location: Phoenix AZ
Posts: 715
|
Well 2 things I'd suggest - measure the voltage you get at the red wires to the top of the Central Electric (fuse) Panel? is it what you see on the battery or somewhat like what you see on the dashboard...?
If its less than battery voltage - disconnect the battery and clean all the connections to the engine jump post. If its just like the battery level - you likely have terminal contact issues in the dashboard pod connections - I'd clean them all and reassemble.. also the ground point connections above/behind the dashboard. Alan
__________________
1994 928 GTS Black/Black Manual |
||
|
03-19-2008, 04:34 PM
|
|
|
|
Registered
Join Date: Jan 2007
Posts: 11,758
|
Blinking dash light is often an indicator of worn brushes in the alternator barely making a connection. The alternator would test out as good.
|
||
|
03-19-2008, 05:40 PM
|
|
|
Architecture & Porsche's
Join Date: Jan 2006
Location: Austin, Texas
Posts: 3,189
|
gonna clean the grounds & wires this weekend. The alternator is new (500 miles now since this report). I think what happened is that something broke inside the alternator & it shorted, causing it to back-charge the signal-to-charge wire. I do not have 12v coming from this wire although I have continuity. Also, the alternator bench-tested good, but shorts when trying to signal-to-charge it upon starting the car, so a new alternator was chosen.
Still have the blinking lights, used another switched 12v source to connecto to the signal-to-charge line, alt works fine, nice & strong, though blinking light still one. Waaah.
__________________
Porsche Club Racing National Scrutineer '89 Andial 951 '82 928R '74 911 RSR 3.6 |
||
|
03-20-2008, 08:43 AM
|
|
