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Power disappears when trying to start, GEN light on, 71 Eldorado

Started by mummyjohn, March 07, 2015, 07:01:43 PM

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mummyjohn

Trying to trace the source of this phenomenon.  Backstory:
I was driving around yesterday and noticed the 'GEN' warning light on the dash was faintly illuminated.  About two miles further along I was waiting to turn left at a traffic light and by now the light was much brighter.  My turn signals had stopped working.  Headlights were still on, radio was still on.  Then (there idling at the light) the car slowly stopped running, almost like a train running out of steam.

That was last night.  The battery has full voltage, everything electric works: interior lights & seat back release when you open the doors, radio, windows, headlamps/tail lamps.  But if I try to actually crank the car, I get it turning for barely a fraction of a second then everything goes dead.  Not the clicking like when a battery's low, just outright nothing.  Releasing the key from the starting position and everything is fine again.  The radio presets are all gone though, something that only happens when replacing the battery, normally.

It's a strange problem and I just wouldn't even know where to start.  I was going to go through the list of instructions they have in the manual in the starter section, but I figured I'd ask here to see if anyone knows some way of saving me lots of time!


Also: the 'GEN' light does come on with the ignition on the ON position and the car not running (as it should).
- E. Ringman

1971 Eldorado coupe

joeceretti

Load testing your battery might be an easy first step. I've seen this very thing happen with a failed battery. Full voltage but not full current under load. Especially evident when cranking the starter. It's happened to me twice and this very thing happened both times.

bcroe

I also think its the battery.  But it could be a high resistance connection somewhere else in
the battery to starter circuit.  I check this by opening the hood, turning the key to start for
10 seconds, then jumping out and seeing if a battery terminal is hot.  good luck, Bruce Roe

Smedly

Sounds to me like just a bad connection on the battery. try just twisting the cable at the battery and see if you can move them. maybe take the cables apart and clean up with a battery brush.
When a Doctor "saves a Life" it does not necessarily mean that that life will ever be the same as it was, but he still saved it. My 46 may not be as it was but it is still alive.
Sheldon Hay

mummyjohn

Will do a current test tomorrow.  I'm hoping something as simple as the battery being tired is the problem.

What worries me is that that doesn't explain the car suddenly "dying" in the street (does it?).  If the engine's running, shouldn't the generator be providing plenty enough to keep the spark plugs sparking?
- E. Ringman

1971 Eldorado coupe

James Landi

try cleaning the main alternator connection that goes to the battery.  I had a 72 Eldo that had a layer of high resistant gray crud on the connecting  3/8""crimp loop" at the B+ alternator output. Disconnect your battery, and use a socket wrench to free that wire up.  You'll likely find your problem... you need to clean that connection with sand paper or change out the crimp loop. 

76eldo

Another problem area is the positive wire post on the starter.
The battery and the other positive wires are connected together there. That area is subjected to a lot of heat and grease and needs to be serviced periodically.

The wires carrying the current back to the charging system and ignition could be faulty or the connection could be dirty.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

mgbeda

Definitely sounds like a bad connection.  I like Brian's idea because it's the one place where a single bad connection will cut off power from the battery AND the alternator.

The positive feed from the alternator and (obviously) the positive feed from the battery meet at the + battery terminal.  Usually even if the + battery terminal is off the battery those two wires remain connected at the lug, but it's possible they are separately connected (lots of things get changed on a 45 year old car).

-mB
-Mike Beda
CLC #24610
1976 Sedan DeVille (Bessie)

Jon S

Do you happen to have a battery cut off switch on the car?  Those green knob cut offs are known to cause this type of problem.
Jon

1958 Cadillac Sedan De Ville
1973 Lincoln Continental Coupe
1981 Corvette
2004 Mustang GT

Lucas Feininger #15674

I have a mildly amusing story about those green switches. Years ago I took the family for a ride in my 63 convertible. At one point we stopped. When I tried to start the car again it was dead as a doornail. I checked all the connections, jiggled wires, etc. -- nothing. No starter, no lights, no horn. In frustration I closed the hood "abruptly" (I don't want to admit to slamming it). Getting back in the car I tried it one more time -- engine started immediately and we made it home.

After I calmed down I thought about what I had done and decided that maybe it had something to do with the battery shutoff. Sure enough the little green wheel was just a little bit loose. Closing the hood had jarred the wheel enough to re-establish contact. Now I make sure the wheel is nice and tight every time I open the hood.

I hope your problem turns out to be as simple as mine.

Lucas Feininger
1965 Sedan de Ville
1965 Eldorado
2014 SRX
CLC #15674

"The only way to travel is Cadillac style"