Battery and alternator replaced, but TJ still keeps dying

Ten Dimes

Ten Dimes

New Member
Joined
Apr 18, 2020
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Location
Jacksonville
So the battery died on me. I was able to get it jumped and went to autozone and got a new one. They said it may need a new alternator since the voltage on the battery wasn’t going up. So I order one off rock auto and put it in Wednesday. Drove it around for about 45 minutes with no issues. Friday my girlfriend went to drive it to the store and it was dead. When I got home the dome light wouldn’t even come on. We rolled it out of the garage and the lights came on and it started up. Turned it off and it wouldn’t start again. It seems to have an electrical issue. When I went to check it this morning no dome light. While I was siting there with the door open all of a sudden the dorm light turned on and I was able to start up the Jeep. It keeps going in and out with the light coming on randomly. I’ll check the voltage in both cases and it’s always around 12.6 v. The positive terminal cable is hot which makes me think it may be a bad cable. I’m lost at what else to check. Any one have suggestions?
 
Absolutely...replace that entire cable man.
 
This issue is generally simple and fairly obvious (once you find it that is). Great advice above. This is how I would attack it:

  1. Remove both battery terminals (negative first)
  2. Check + connection at the starter
  3. Check + connection at alternator
  4. Check battery cables and terminal integrity
  5. Check - ground cable connection at block and firewall
  6. Clean battery terminals and posts
  7. Re-install cleaned terminals, + first - last
  8. Charge battery at lower amp setting (maybe 10 amps) for 6 hours or trickle charge for 12+ hours (not a fan of high amp charging unless emergency)
  9. Load test fully charged battery with actual load tester (the one with a heating coil) (new batteries can be defective)
  10. Start vehicle (optimism)
  11. Use a volt meter across the battery with vehicle running
  12. Expect to see approximately 13.8 to 14.3 output voltage from the alternator
  13. Much less output could mean bad alternator
  14. Much more voltage could be bad alternator
  15. If all steps pass these tests after doing the above and you still have issues, it is time to look for shorts or component problems
  16. Not impossible but, excessive starter draw and or ignition switch issues are not out of the ordinary.
  17. Always remember when diagnosing electrical issues, find last known point of voltage and work your way forward.
This tool should be part of any mechanic or hobbyist's go to tools:

https://www.amazon.com/gp/product/B000AMBOI0/?tag=wranglerorg-20
 
With the engine off check voltage at battery. Start the engine. Check the voltage at the battery. If the voltage isn't up in the 13-14 volt range at the battery then it isn't getting power from the alternator. So check the voltage at the alternator. If it IS showing 13-14 volts, then there is a problem with the wires. If it ISN'T showing then there is a problem with the alternator.
Either way, it is a very good idea to clean all corrosion off battery and alt cables. Pos and neg. Check all ground wire connections as said above.
 
As Flivver250 mentioned. I was one of those people that thought my battery was shot and my new battery defective. Turned out my starter was shot. It was pulling 200 amps. It would start just fine then later after a short stop wouldn’t start again. I had good charge and good voltage on the battery until I hit the starter. I didn’t know a starter could do that. I don’t know what the cab light looked like, I frequently drive doorless so that has been disabled for some time.
 
TJScott said:
As Flivver250 mentioned. I was one of those people that thought my battery was shot and my new battery defective. Turned out my starter was shot. It was pulling 200 amps. It would start just fine then later after a short stop wouldn’t start again. I had good charge and good voltage on the battery until I hit the starter. I didn’t know a starter could do that. I don’t know what the cab light looked like, I frequently drive doorless so that has been disabled for some time.
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At home I have an analog Snap-On starter draw meter you place over the battery cable and it tells you starter draw. Bought it 40 years ago. It was common to test the starter when we were doing work under the hood. Great for diagnosing and great for predicting future events. Made it easier to sell a starter before it went belly up.
 
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