Hey guys the P5 died on me today, my wife left the lights on for about 20 mins and i had to get a boost when I got back to the car. I thought well it just went down enough to need a jump, and drove off but the radio started to turn off and the air bag light started to come on and flicker so I had to keep the revs up to keep everything on. Now I have noticed a whine for a few days thought it might be the trans something unrelated but now I think it might be the alt.. the light on the dash didn't come on at all though, do you guys think it would be the battery its self or the alt and bat? Halp I got to go back to work on boxing day.
Car died halp!
- Thread starter MadOnion
- Start date
TheSwapnessMonster
Member
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- mazda
If a car battery is drained below a certain voltage, it dies and cannot be recharged.
Check the voltage at the battery with the car off. It should be about 12 volts. Then start the car and check the volts again... It should jump to 13 or 14 volts.
The battery light doesn't necessarily come on to indicate an alternator failure depending on how it fails.
An easy old school trick is to disconnect the negative battery cable with the car running.
If the car keeps running the alternator is good... If the car stalls the alternator is bad.
Some people say never to do this.. You can blow stuff up but I have done it at least three times on my P5 with no problems.
The dead battery may have been the last straw for the alternator and pooched it or your working alternator is struggling to charge a cooked battery as well as run the rest of your car.
If you can still start the car it generally means you've got a good battery with enough power to run the starter motor.
The battery light doesn't necessarily come on to indicate an alternator failure depending on how it fails.
An easy old school trick is to disconnect the negative battery cable with the car running.
If the car keeps running the alternator is good... If the car stalls the alternator is bad.
Some people say never to do this.. You can blow stuff up but I have done it at least three times on my P5 with no problems.
The dead battery may have been the last straw for the alternator and pooched it or your working alternator is struggling to charge a cooked battery as well as run the rest of your car.
If you can still start the car it generally means you've got a good battery with enough power to run the starter motor.
Do not remove the battery cable from the battery while the car is running. You will burn out the diodes in the alternator. Take the battery to any auto parts store and ask them to charge it and then load-test it. If the battery is bad, then get a new one. If not, have them test the alt. I wouldnt but batteries or alts just to see if these solve the problem, as they usually cannot be returned (electrical)
TheSwapnessMonster
Member
- :
- mazda
Idk about Canada, but Autozone and Advance Auto in the US can test your battery, starter, and alternator for free in about 30 minutes by measuring electrical load.
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This. I would never remove the negative batt cable on any modern car. That is a really good way to burn up some electronics. It was a good method back in the day when cars didn't have any electronics. Also, don't just be a parts replacer...diagnose then repair.
From your last post it does sound like the alternator is bad. It's very simple to measure the voltage with the car running and not. I would never replace an alternator or battery without doing this. If you don't have a multimeter, go buy a cheap one from a discount store. Or I believe Autozone will also check this for you. Autozone will definitely bench test both parts out of the car.
The alternator isn't terribly difficult to replace, but it is a pain in the butt. I wouldn't do it unless I was sure it needed it.
The alternator isn't terribly difficult to replace, but it is a pain in the butt. I wouldn't do it unless I was sure it needed it.
The alternator is a pain to replace because it can be completely removed from the engine but is trapped in the engine bay.
You can remove it from the top by removing a bunch of parts or remove it from the bottom by removing the axle.
One mechanic discovered through trial and error that you can remove the joint shaft bolts and pull the axle from the transmission about a quarter of an inch. This allows the axle to wobble a bit out of the way and give just enough room to squeeze the alternator past it.
This allows you to remove the alternator from the engine bay without removing all kinds of parts... it doesn't drip any transmission oil and you don't risk damaging the oil seal on the transmission.
The alternator on our car is a bit weird and different in that it has a control wire that runs directly to the ECU and the ECU controls the output of the alternator. If that wire is broken or has a bad connection the alternator effectively shuts off.
Some people have installed 3 altenators before finding one that works. The rebuilds can have problems.
You can remove it from the top by removing a bunch of parts or remove it from the bottom by removing the axle.
One mechanic discovered through trial and error that you can remove the joint shaft bolts and pull the axle from the transmission about a quarter of an inch. This allows the axle to wobble a bit out of the way and give just enough room to squeeze the alternator past it.
This allows you to remove the alternator from the engine bay without removing all kinds of parts... it doesn't drip any transmission oil and you don't risk damaging the oil seal on the transmission.
The alternator on our car is a bit weird and different in that it has a control wire that runs directly to the ECU and the ECU controls the output of the alternator. If that wire is broken or has a bad connection the alternator effectively shuts off.
Some people have installed 3 altenators before finding one that works. The rebuilds can have problems.
I replaced to alt through the top and needless to say it was a b**** but I just moved the cruise and charcoal canister. It was still a dick to get out and then back in but I did it in about two hours.. Here's hoping it was a good alt it was bench treated before I bought it and it had 3 year replacement ******* 300 bucks later we'll see if it all worked out tomorrow
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Got the alt in and it seems to be charging and running okay but now when you stop the rmp goes down to like 100 when you put the clutch in until you stop at the light then I comes back up but only once you stop moving its really strange
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