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Electrical Problem


Tommg's Avatar
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08-21-03, 09:02 AM   #1  
Tommg
Electrical Problem

1985 Mazda RX7 GSL-SE 13B Fuel Injected engine.

A couple of days after having a radio installed, the car wouldn't start. It has a new battery and new starter. It seemed to have zero battery; didn't crank or click. The radio would turn on but there was not enough power to rotate the hidden hidlights. I jumped the car and it started right up, but wouldn't re-start. The dashboard voltage meter indicated 14 volts.

The following day, I was going to charge the battery, but first tested it with a voltage meter, and got the reading of 12.5 volts with the positive cable removed.

Suggestions? Thanks in advance!

Tom

 
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08-21-03, 09:09 AM   #2  
Joe_F
Sounds like a hokey radio installation. My guess is they hooked something up wrong and it's draining your battery.

Back to them and have them correct the problem for you. Failing that, do a charging system test as I have in my "The Basics" below.

 
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08-21-03, 09:32 AM   #3  
Tommg
Another Question

Thanks, Joe!

Should I run the voltage test on the battery terminals after I get the car started? And then turn on accessories one at a time to test for fluctuations?

If I find the offending accessory, will there be a drop in voltage?

Thanks!

Tom

 
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08-21-03, 10:00 AM   #4  
Joe_F
Charge the battery up (assuming the battery is good).

Then, do the test. Tell us what you find. Chances are if it's not putting out 13.5 volts or better, you have an alternator/charging system problem.

If it JUST occured recently after the stereo install, I'd be looking there first.

 
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08-21-03, 10:41 AM   #5  
Tommg
If the battery tests 12.5 before charging, doesnt that indicate it doesnt need a charge?

 
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08-21-03, 01:18 PM   #6  
Joe_F
Ya, 12.5 is good for a battery to start with.

 
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08-21-03, 02:18 PM   #7  
Tommg
Resolution?

I reconnected the battery cable to run the voltage tests and it started right up. I am praying that this means that the lunitics who installed the stereo left the cable "almost" tight.

When running, the altenator put out 14.x volts and none of the accessories seemed to drain the voltage.

Thanks again for your help!!

Tom

 
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08-21-03, 07:28 PM   #8  
Thats what it sounds like. Get back to the radio shop and get them to hook it up properly. They tend to do that. It sounds like where ever they have it connected is definately draining the battery.

On a side note. 12.5+/- volts with a DVOM does not necessarily mean that the battery is good. The battery requires a certain level of AMPs to properly crank the engine over. ie CCA and CA, cold canking amps and cranking amps. Low amps would for the most part indicate a bad cell in the battery. Although I dont think this is your problem.
Hope this helps,
Billy

 
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