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Replaced generator on 78 Eldorado and still not charging battery

Started by Tornike, September 15, 2018, 10:52:43 PM

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Tornike

My battery has not been getting any charge from the alternator since I got the car.

Generator light on dash would not completely go away while engine running and would stay dim. Multimeter was reading 12.4v both at engine on and off states at the battery terminals. I replaced belt and alternator with new ones from AZ.. generator spins fine. But no power. Didn’t solve my problem.

The generator light on dash now completely goes away when I start the car and comes back after a minute or so, slowly getting brighter. Same 12.4v reading at the battery terminals.

According to the service manual, While ignition Switch on, I tested:
B-post and ground (generator chassis) - reading was 12.36v
Generator terminal 2 and same ground - reading was 12.36v
Generator terminal 1 and same ground - reading was 1.5v

I don’t think there is any parasitic draw from the car, as about 5 days later car started just fine and battery voltage was the same.

Where should I look for problems first?

bcroe


Tornike

Bruce, is there reason why the generator bulb will go off after starting the car (meaning that alternator probably has started) and then gradually come on again after a minute? This started happening after I replaced alternator.

As I can’t read more than 12.5v at the battery terminals while car running, which is more likely, for the alternator to shut off shortly after due to short etc., or for the wiring to the bulb / or bulb itself be faulty? Thanks

bcroe

Its not the bulb, fix/replace the alternator.  Probably reving up
the engine would start up a good alternator, even with the bulb
disconnected.  Bruce Roe

Tornike

Will try revving engine for a minute or so and see. As always, Thanks Bruce!

Scot Minesinger

It is not unusual to install a dead on arrival (DOA) alternator, happens a lot.  Also check the connector at the alternator, those are low quality and often go bad.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Tornike

Thanks Scot, I will check in the morning as Bruce suggested and Autozone rep will have a bad day if it’s a bad alternator as he was insisting on this particular model with ‘limited lifetime warranty’.
The connectors seem fine, as the voltage goes through them from the battery..

Scot Minesinger

One time, I suffered two in a row DOA, and this is likely because it was returned as bad and then not dealt with properly at either the parts store of the re-builder and it is resold as new.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Tornike

What would be the best bet from your experience quality-wise, or are they all same junk

CarQuest reman from Advance Autoparts https://shop.advanceautoparts.com/p/carquest-alternator-remanufactured-63-amps-7127-12a/5210097-P

Remy reman from Rockauto https://www.rockauto.com/en/catalog/cadillac,1978,eldorado,7.0l+425cid+v8,1025930,electrical,alternator+/+generator,2412

Napa reman (55-63amp) https://www.napaonline.com/en/p/RSE2134011A

Or Napa NEW (it says 37-63amp) https://www.napaonline.com/en/p/NNE1N4011A

From what I’ve been reading so far all the above-mentioned brands have decent rate of DOA. Thanks Scot for pointing that issue out!

I guess rebuilding original one on a long run as Bruce suggested might actually be a choice for me even though I didn’t want to take my limited weekend hours away from fixing something ‘more important’ into fixing an alternator.

Cape Cod Fleetwood

I had to replace my alternator a few months ago, used an Autozone, so far, so good.

\m/
Laurie
There are 2 kinds of cars in the world, Cadillac and everything else....

The Present -1970 Fleetwood Brougham

The Past -
1996 Deville Concours
1987 Sedan De Ville "Commonwealth Edition"
1981 Coupe De Ville (8-6-4)
1976 Sedan De Ville
1975 Sedan De Ville

The Daily Driver and work slave -
2008 GMC Acadia SLT *options/all

"Cadillac Kid" Greg Surfas 15364

Tornike,
If I was you I would check the connection where the positive battery pigtail (small 10 gauge wire) connects with the wire leading to the post on the alternator. 
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Tornike

Quote from: "Cadillac Kid"  Greg Surfas 15364 on September 16, 2018, 12:57:18 PM
Tornike,
If I was you I would check the connection where the positive battery pigtail (small 10 gauge wire) connects with the wire leading to the post on the alternator. 
Greg Surfas
Thanks for tip, I checked it yesterday. The cable is actually little worn at the battery terminal connection (Where the red plastic is), but I’m pretty sure still takes power thru it. I verified this by checking terminal 2 on battery and ground (alt housing) with ignition on, which gave me 12.36v reading, close to the battery voltage (12.4v). Then I disconnected that small 10 gauge cable from B post of alternator and instead ran a jumper cable from B post of alternator to the positive terminal of battery to make sure that 10 gauge wire was not a problem and started the engine. I saw no changes whatsoever..

savemy67

Hello Tornike,

If you have checked all the associated wiring and connectors under load, then it seems most likely that you have a defective alternator (again).  You could rebuild your alternator, which is not too difficult or expensive.  You can read about how I did mine here:

http://forums.cadillaclasalleclub.org/index.php?topic=133691.60

(I think it is reply 74).

I have a '67, so I think the only difference is your alternator has an integrated regulator, and higher current output.  Otherwise both years are very similar.

If you buy a third replacement alternator, and get the same voltage reading charging your battery, you may need to convince the parts store to research the batch or lot number for the rebuilt alternators.  Expect to get a little flack from the parts store.  Some parts stores will check your charging system for free (hoping to sell you a new alternator).  The trouble is that the parts store employee may attempt to blame something else on the car when they realize the defective alternator is one they sold to you, so have your ducks in a row.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Tornike

Quote from: savemy67 on September 16, 2018, 09:13:46 PM
Hello Tornike,

If you have checked all the associated wiring and connectors under load, then it seems most likely that you have a defective alternator (again).  You could rebuild your alternator, which is not too difficult or expensive.  You can read about how I did mine here:

http://forums.cadillaclasalleclub.org/index.php?topic=133691.60

(I think it is reply 74).

I have a '67, so I think the only difference is your alternator has an integrated regulator, and higher current output.  Otherwise both years are very similar.

If you buy a third replacement alternator, and get the same voltage reading charging your battery, you may need to convince the parts store to research the batch or lot number for the rebuilt alternators.  Expect to get a little flack from the parts store.  Some parts stores will check your charging system for free (hoping to sell you a new alternator).  The trouble is that the parts store employee may attempt to blame something else on the car when they realize the defective alternator is one they sold to you, so have your ducks in a row.

Respectfully submitted,

Christopher Winter
Thanks for your .02, Christopher.
Have to say, I’m truly Fascinated with your thread on a 67 sedan deville! Such a good read! Past two hours went unnoticed into reading all 7 pages. And I could keep reading.
I’m pretty sure lots of people would enjoy watching all of your journeys and detective work on Youtube.

TJ Hopland

Pin 1 on the generator should also be at system voltage when everything is on and running normally.    Pin 1 is what tells the regulator circuit to 'turn on'.     Does the gen light come on nice and bright when you first turn on the key? 

To test the alternator take a jumper wire from either of the other terminals and see if that kicks it up to a more reasonable voltage.   If it does you know the alternator is fine.   Don't leave it like that, that will drain the battery when the engine is not running and could also leave other things inside the car turned on. 

So assuming the alternator works next thing would be figuring out why you are not getting voltage on pin one from the dash.   The wire runs from pin 1 to one side of the 'gen' light in the dash.   The other side is connected to some fuse that comes on with the key.   The detailed drawings you posted have that cut off so I can't tell you for sure which fuse it is.   When the alternator isn't spinning pin 1 basically is a ground.   This means when you turn the key on you are putting battery voltage to one side of the bulb and the other side is basically grounded through the non spinning alternator.   Result is bulb lights up.   Start the engine and the alternator turns and pin one 'sees' battery voltage coming through the bulb and turns on the regulator.   Regulator on and alternator spinning you should be getting something higher than the original battery voltage.   Bulb is now seeing system voltage on pin 1 and system voltage from the key so light does not light because there is no ground. 

What could be happening in your case is the fuse that feeds the light is blown or there is some funky wiring or connections that are not letting that voltage get to the alternator.   Since that fuse likely shares with something else you are getting some sort of interaction with that other device perhaps acting as a ground for the bulb so when the alternator is spinning you are getting a little voltage bleed from pin 1 feeding the bulb and the other device acting as the ground so you get a little glow out of the bulb.   This is where the question of does the bulb light bright when the key is first turned on,  it should.   If you have the key on and unplug the small alternator connector the bulb should go out.  IF it stays on you have a wiring problem somewhere between the bulb and alternator connector.   IF it doesn't turn on with the key first on then you have a problem between the fuse and bulb or possibly the ignition switch and fuses. 

Does everything else electrical seem to work in the car?   If not then I would be focused on the ignition switch to fuse box side of things.  There are 3 feeds from the fat battery wire on the starter to the rest of the car and they are fusible link wires.  One feeds the headlight switch.   Another feeds the half of the fuse box for the stuff that is always on.   The last one feeds the ignition switch that then in turn feeds the rest of the fuse box for the stuff that is only on with the key.   Often times one of those link wires fails for one reason or another and instead of fixing it people get creative and jump the working section to the non working section which can cause a lot of odd interactions not to mention overloading the remaining section which then often leads to more creative bypassing to keep things sort of working.   The fusible link section of those wires is the first about 18" from the starter to a spice where they splice back to regular wires and join the main harness.   If there isn't a problem with the fusible links the next common place for an issue is the bulkhead connector over by the brake booster.   Its got the identical pins in it to the 1 and 2 connector at the alternator.  The male side is on the engine side, female is the back of the fuse block.   They can get moisture in them or just get loose over time especially the main power ones because they tend to be close to overloaded even when everything is normal.             
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason