Losing battery power

Tiny
LITTLEDRIFTYATA
  • MEMBER
  • 1990 MAZDA MX5
  • 1.6L
  • 4 CYL
  • 2WD
  • MANUAL
  • 190,000 MILES
I've changed through 4 alternators and 3 batteries at this point I'm still losing battery power. The car will dim the radio will shut off my speedometer will shut off rpm meter won't respond car starts sputtering out. I'm lost please help.
Monday, November 25th, 2019 AT 9:01 PM

1 Reply

Tiny
JONNYB1963
  • MECHANIC
  • 252 POSTS
Good morning,

That sounds frustrating for sure. Before we get too far I need you to do two simple tests for me. These tests will help us get to the bottom of the problem more quickly.

You will need a battery charger and multi-meter to do this test.

Step 1. Charge the battery fully with the battery charger. When the battery is fully charged, disconnect the charger from the battery.
Step 2. Set your multi-meter to read DC volts.
Step 3. Place the positive (red) lead of the multi-meter on the positive (+) battery terminal. And the negative (black) lead on the negative (-) battery terminal.
Step 4. Read the voltage indicated on the multi-meter. (Should be around 12.6 volts on a new battery that is fully charged)
Step 5. Leave the meter connected to the battery and start the vehicle and let it idle.
Step 6. Read the voltage on the meter again while the engine is running. (Should be around 14.5 volts)

Come see me again here and let me know what the voltages are that you are seeing.

The first test is to see how well your battery will hold a charge.
The second test is to determine how well your charging system is operating.

Let me know!
Jon
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Tuesday, November 26th, 2019 AT 5:03 AM

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