: yet ANOTHER problem with my 90.....



Reverend Hearse
09-18-11, 01:57 PM
while driving the other day i noticed the dashlights dimming while i hit the brakes. after i shut off the car it wouldn't restart. i had the battery tested and it showed to have a bad cell, so i replaced it. drove fine all day yesterday until last night. i went to the gas station,, shut off the car and it wouldn't restart. got a jump and limped home. there was a definite change in how the car was running in the way back. i used my volt meter to check the output of the alternator and showed 12.2 at the charge post. the battery showed 12.3 . both of those numbers are at idle. i removed the alternator and had it tested and it passed. but i seem to remember numbers of 13.1-13.9 being more normal at idle, could the one volt drop be causing that big of a difference or should i be looking elsewhere? i have test lights, meters ,etc,and a working knowledge of how to test circuits, i just don't know where to look. a wiring diagram would be helpful as well if anyone has one .

The-Dullahan
09-18-11, 02:00 PM
You may well have another issue, such as a short, but that should not matter while driving. My stock alternator always put out about 14.8V at idle. Also, I once got a Walmart battery and they did not put in one large enough for the car, instead putting in a smaller one, which they believed was correct, in spite of my protests. This resulted in about the same story as you tell here.

outsider
09-18-11, 02:14 PM
yeah, should be up between 14 and 15 volts at idle in my experience. 12.2 is definately too low and to me shows that the battery is not being charged as what the battery should be at when not charging.

Reverend Hearse
09-18-11, 02:17 PM
as i drive, the lights get dimmer and dimmer, the radio goes off , basically i lose everything that is power. the battery i bought is 700ca 850cca. i have cleaned all of the connections. im at a loss for this one.......

outsider
09-18-11, 03:08 PM
yup, definitely not charging the battery. I'd have the charging system tested

sven914
09-18-11, 07:00 PM
The alternator belt might be slipping if you haven’t replaced it in a while.

Reverend Hearse
09-24-11, 05:04 AM
ok,i installed a 100 amp alternator, new belt , rechecked for continuity in the wires between the charge post and battery, as well as between the ground terminal and its connection, put another new battery, checked all the fuses, fusible links , and still the battery will not charge. does anybody have access to alldata or mitchell to get me a specific wiring diagram for my car? the haynes book i have is garbage and shows only generic diagrams. im beating my head against the wall and start a new job tuesday, i need to drive my caddy baaaaaaad.....

outsider
09-24-11, 10:49 AM
I'm sure someone here has the 90 FSM and can give you the pertinent pages!

Reverend Hearse
09-24-11, 02:43 PM
i certainly hope so..... this is putting a damper on life

sven914
09-24-11, 03:24 PM
Does the "NO CHARGE" light come on? Of the bulb is burned out, the alternator will not charge the battery.

The-Dullahan
09-24-11, 04:38 PM
Ooh yeah. Hadn't thought of that. Test the bulb next time you have your keys out there.

Reverend Hearse
09-24-11, 10:00 PM
no charge light works fine...

Garys
09-24-11, 11:30 PM
With the engine running, your amp meter should be showing 14.5 volts. If it is still showing 12 something, jiggle the wires and the plug on the alternator and see if the amp meter changes and starts to show that it's charging. Also, you could have a baaaaad replacement alternator.

Reverend Hearse
09-25-11, 12:10 AM
it will stay running when disconnected. it has me baffled to no end. usually im really great at fixing things of this nature.

sven914
09-25-11, 12:26 AM
With a computer controlled car (such as a '90 Brougham) it is not a good idea to disconnect the battery with the engine running. It can damage the computer.

Reverend Hearse
09-25-11, 01:11 AM
its not really computer controlled is it ? it has a few plugs on the carb, and a few sensors on the motor, but not really anything like in a newer car...

Garys
09-25-11, 01:24 AM
It has an ECU, but you are right, nothing like a fuel injected car. Your charging issue has to be a fairly easy fix. (easy for me to say) I would start with the basics, like the condition of your battery cables and making sure you have a good ground. Your lights dimming when the brake lights come on could be a low battery but it could be a bad ground too.

Reverend Hearse
09-25-11, 01:38 AM
i know one of the wires to the regulator sends a reference voltage from the car to the alternator to tell it how much to charge the battery. what are the normal parameters of the reference wire? does that wire pass through the ECM at all ?

sven914
09-25-11, 01:41 AM
The computer in your car is simplistic, but it controls the ignition timing and the mixture solenoid. If you happen to have, at you disposal, an antiquated carburettor and a vacuum powered distributor, you can replace your computer with a box of matches. But, if you don't have those things, and the computer were to die, the engine would be a glorified paper weight.

csbuckn
09-25-11, 05:05 AM
Here's some pics of the 90 FSM.
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0135.jpg
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0136.jpg
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0138.jpg
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0141.jpg
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0140.jpg
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0139.jpg

jayoldschool
09-25-11, 04:19 PM
Please, don't do the disconnect battery while the car is running thing. There are correct ways to test the alternator, and this isn't one.

Reverend Hearse
09-25-11, 04:28 PM
Thanks a million!!! Im headed out now to check everything over again....

Reverend Hearse
09-25-11, 04:56 PM
i went and checked the car again according to the FSM, with the car at fast idle i see 11.9 , but at normal idle it shows 12.1. i suspect the new alternator may be faulty, however the one i replaced showed the exact same numbers and yet bench tested at 15.1. i am taking it and the battery back out so i can have them tested/replaced yet again. outside of faulty parts i cant see a reason for the problem...

jayoldschool
09-25-11, 08:27 PM
Inspect, clean, lube, and tighten all your battery cable and ground connections. I would bet that this is the issue.

Reverend Hearse
09-25-11, 08:49 PM
im replacing all of the cables this week sometime, i cant see it being any other thing. i just had the new alternator tested and it passed with flying colors....

jayoldschool
09-25-11, 09:00 PM
I replaced the cables on my 81. It made a huge difference.

Reverend Hearse
09-25-11, 09:27 PM
would the cables being bad make it show low voltage at the charge post? i guess that could explain why it passes with normal voltage on a bench test...

KrisK
09-25-11, 09:50 PM
would the cables being bad make it show low voltage at the charge post? i guess that could explain why it passes with normal voltage on a bench test...

Yes, bad wires will cause you to lose voltage. I agree with the cables being your problem. You should remove your cables and replace them with high quality ones.

Reverend Hearse
09-26-11, 03:00 PM
took the car to the auto parts store today , i charged the battery all night and it showed 13.1 when i woke up. it is still only putting out <30 amps when it should be 100 amps. im going to use my limited funds to purchase battery cables tomorrow in hopes that there is some unknown resistance in the wires that is causing this problem. the car still starts first hit of the key, and all the accessories are working..... im seriously ready to derby this thing if i cant get it fixed soon.... im starting to want a japanese econobucket more and more ..... ready to cleanse the driveway of all that is cadillacrap

sven914
09-26-11, 03:43 PM
^If it doesn't stay running, how are you going get it to last through a demolition derby?

Reverend Hearse
09-26-11, 03:50 PM
touche....... well played ,sir........

thesameguy
09-26-11, 10:15 PM
Please, don't do the disconnect battery while the car is running thing. There are correct ways to test the alternator, and this isn't one.

That is a fact! Most voltage regulators rely on the battery as part of their circuit, and removing the battery can cause the voltage output of the alternator to spike wildly - like blowing up light bulbs wildly. Disconnecting the battery can fry everything electrical in your car, including the alternator itself. Do not disconnect it while the car is running!

For all intents and purposes, alternators are "on demand" - they should always be putting out approximately 14.5v, but amperage will vary based on electrical demand. With the car running but not much else (lights, stereo, etc.), you shouldn't see much amperage... on a CCC (or whatever Cadillac-speak was for that system) vehicle perhaps 25 or 30 amps... all you're powering is a dumb computer, mixture solenoid, an oxygen sensor, and the ignition system.

If the alternator is known-good and the battery is known-good, you've either got a problem with the idiot light (like an incorrect wattage bulb) or bad wiring. Don't forget the ground cable is as important as the positive cable! FWIW, every older GM vehicle I have ever owned has had pitiful wiring between battery and alternator - you should see what passed for acceptable on my '84 Suburban!

If you're seeing 13.1v with the car off on the battery, you've got a healthy one. You need to test voltage at the alternator itself and compare it against values at the battery with the car running. I'm sure you could also test resistance on the battery cables too, but I have no idea what separates "good" from "bad" there.

Reverend Hearse
09-26-11, 11:29 PM
i am taking it to the shop i bought the alternator from in the morning. i called them today and explained what is going on. the bulb hasnt changed , and it still functions. nothing had been changed/adjusted/fondled between the time it last charged and when the problems began.im out of ideas and patience , so ill let the ''pros'' handle it now ....

Reverend Hearse
09-27-11, 09:12 PM
got the car fixed today , took it to the electrical shop and in under a hour they had it going .. the culprit? a bad / loose p/s pulley.... replaced the belt and now it spins up properly... the things i overlook sometimes... apparently its a common problem with the olds 307 because the water pump drives the alternator but the water pump is only driven by the p/s pump......50 bucks later, it is on top of the world again.....