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2006 SRX 2000 Deville 1994 Seville STS
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71 Posts
Discussion Starter · #1 ·
My batter y keeps draining overnight and once jumped it starts right up. I just replaced the negative cable, the positives cables are fine. I gave it jump and drove it for about a half hour, parked came back and it won't start. At autozone they made me by a digital multimeter and told me to check the fuses to see which one is causing the drain. I've searched the forum and read alot up on this but still kinda confused on how to do this or where to start. Like what should this thing read normally for each fuse or how to set it? If anyone can help thanks in advance.
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,648 Posts
Not sure about parasitic loads in a 1994, BUT, with everything off and quiet the amperage draw of a car with RAP dropped out (IF you have RAP) should be on the order of 15 - 25 mA. (.015 A). Checking this can be a problem because RAP (Retained Accessory Power) keeps some stuff energized for 10-15 minutes after Key:OFF, then it drops out. You have to insert the VOM in series with either the positive or negative battery cable - so it reads ALL battery draw - and let the car settle down for a half hour or so until the RAP drops out. Then you read the amp draw -say it's 1 amp. Something's wrong. Now you pull one fuse and/or relay at a time until the draw drops to the aforementioned 15-25 mA. This is particularly a PITA in a vehicle with a fuse box under the rear seat because you have to get into the car, squat down, and wait for RAP to drop out. It all takes time, but with an hours' diagnosis you'll find the problem.

You have an aftermarket audio system with remote ON amp ???
 

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2006 SRX 2000 Deville 1994 Seville STS
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71 Posts
Discussion Starter · #3 ·
This is what I have. Can you tell me how to set it and which socket at the bottom to use. And also how to tell the amp draw? If I understand correctly I'm supposed to put the red on the positive battery terminal and the black on the negative battery terminal?

 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
Plug the red test lead in the bottom left socket (DC 10A). Plug the black test lead in the center socket (COM). Place the switch in the DC 10A position. Now you are ready to read NO MORE than 10 Amps of DC current. Having alligator clip adapters for the pointed ends of your test leads would be a big help!

Open all the doors and the trunk and do not move them, put the keys in your pocket, remove the negative cable from the battery. Clip one test lead to the battery terminal and the other test lead to the battery cable you removed (effectively connecting the battery back to the car with the ammeter in the middle). Do not worry about the polarity with a digital meter, the meter will display the correct value even if the polarity is reversed.

Wait 10 minutes or however long it takes the RAP system to time out. The meter reading will change up and down as various modules are put to sleep and a few test routines run. When the meter display has been constant for a few minutes, that will be your final parasitic drain current reading. Mine drops to 30 ma (0.030 amperes).
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,648 Posts
Yeah, that ^^^^

......and with the VOM set up to read amperage, DO NOT connect it to the battery + and - terminals simultaneously: you'll either blow the 10 amp internal VOM fuse or you'll have a handful of melted plastic. If you did that in the amperage mode the VOM would act exactly like placing a bent coat hanger across the battery terminals.

Get the Radio Shack book(s) on basic electricity and/or electronics and do some studying. (Or, read the directions that came with the VOM)
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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Only one true, accurate way to accurately determine battery "efficiency" - drive the car for a while, shut down and remove the battery. Using a second vehicle, take the battery to a chain parts house or local shop and ask them to do a load test. This places the battery in a test rig which has some pretty impressive guts - it will draw down the battery at a controlled rate and thus give a "readout" of battery efficiency and estimated life remaining.

*You can make a SWAG (Scientific Wild Ass Guess) by watching your voltages while starting up and driving - Key:ON - voltage should be 12.4 - 12.6. START (cranking) should show 11.5 to 12.4. RUN should ramp up to 14.6 to 15.2 for a while, then slowly settle to 14.6 or so as the battery reaches full charge. Any low voltages in this sequence and you should suspect a dying battery. Any battery older than 6 years is living on borrowed time, "warranty" notwithstanding.

A fully charged "12 volt" battery, disconnected and idle for at least a half hour, will read 12.6 volts.

* Just saw JimD's post ^^^. Clarification: Set up the VOM for DC Volts. Clip the leads to the proper battery terminals. Fish the VOM up and lay it against the windshield. Watch the numbers jump around.
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
....You can make a SWAG (Scientific Wild Ass Guess) by watching your voltages while starting up and driving - Key:ON - voltage should be 12.4 - 12.6. START (cranking) should show 11.5 to 12.4.
Without an external voltmeter, there is no way 99% of the motoring public can determine the battery voltage during engine start. The DIC goes blank and all systems not required for engine start/run are shut off.

FWIW (and I do recognize battery voltage as ONE important diagnostic tool), my battery voltage routinely falls below 10 volts during the brief period the starter motor is engaged. And yes, I used a decently accurate and responsive external meter to measure the voltage under various conditions. Several times.
 

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97 SLS, 63 Sedan De Ville
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21 Posts
FWIW, I had the identical problem you're describing - "parasitic" battery drain overnight, yet the car would start right up on a jump the following morning and the voltages always looked good. Solution? I replaced the battery. Went a little overboard and bought an Optima Red Top, but hey! It's a Cadillac! The problem has been gone ever since.
 

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1992 Eldorado
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200 Posts
With my car the alternator bleeding back through bad diodes was the problem. Never a code and the voltage always looked fine. I'd start with the simplest things first and rule out both the battery and alternator before looking for parasitic drains.
 

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08 cts 68k, 07 STS-V 15K, 97 Sts 160k
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302 Posts
I just had the same problem last week I charged it for 8 hrs then went to work it was barely starting charged it again over night and the next day when i came out after work it was dead and jumped it to get home. Took it out and went to autozone they put it on the tester and it was bad. it dropped down to 6 volts under load had bad cell in it. The bat was still under warrenty 2yrs and 8 months old. 3 yr warrenty. Free new bat total time 30min including travel time to the autozone. Take it out and get it checked FIRST.
 
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