ericem Posted July 12, 2007 Author Share Posted July 12, 2007 It sounds like the battery charge may be slightly low. The alternator needs to be running with the engine RPMs above 900 for it to put out a fair amount of charging current. You are not going to be able keep a good charge rate going at 500 RPM. ECU was upping idle to 1000+ trying to get the voltage up. And even at 3000rpm's didn't go past 12.5v. But in my dad's truck at idle of about 500rpm's had radio blasting max ac exact same test the voltage did not budge AT ALL. and the idle stayed the EXACT same. Link to comment Share on other sites More sharing options...
Manarius Posted July 12, 2007 Share Posted July 12, 2007 ECU was upping idle to 1000+ trying to get the voltage up. And even at 3000rpm's didn't go past 12.5v.Uh. No. The ECU turned up the idle to compensate for the increased load on the engine based on the AC. Not to get the voltage up Have you load tested the alternator like people have said to many times on this thread? Until you've done that, stop spitting out multimeter readings because they don't have anything to do with anything. The voltage is going to be low at idle because the engine's running slower. That's why when you're at idle, you're running on slightly batteries to make up for some of the lost voltage! The accessories just make the car dig deeper into the battery charge. Link to comment Share on other sites More sharing options...
ericem Posted July 12, 2007 Author Share Posted July 12, 2007 Um ya one sec, ill show you them tommorow its on a paper in my dad's truck. Link to comment Share on other sites More sharing options...
ericem Posted July 12, 2007 Author Share Posted July 12, 2007 Uh. No. The ECU turned up the idle to compensate for the increased load on the engine based on the AC. Not to get the voltage up Have you load tested the alternator like people have said to many times on this thread? Until you've done that, stop spitting out multimeter readings because they don't have anything to do with anything. The voltage is going to be low at idle because the engine's running slower. That's why when you're at idle, you're running on slightly batteries to make up for some of the lost voltage! The accessories just make the car dig deeper into the battery charge. Oh and by the way the ECU does compensate idle for voltage as well. With ac ONLY on im at 700rpm's or less. When i turn on other accesories like the wipers it goes up to 1000+. Link to comment Share on other sites More sharing options...
Manarius Posted July 12, 2007 Share Posted July 12, 2007 Oh and by the way the ECU does compensate idle for voltage as well. With ac ONLY on im at 700rpm's or less. When i turn on other accesories like the wipers it goes up to 1000+.FWIW, the only things the ECU compensates for are headlamps and A/C. My point is that at idle, the voltage is going to be low. Stop asking for 14 volts at idle - it isn't going to happen. The charging system requires the car to be at RPM's higher than idle to charge correctly. When you start draining batteries in normal everyday driving, then you need to take a look at your charging system. Link to comment Share on other sites More sharing options...
OB99W Posted July 12, 2007 Share Posted July 12, 2007 [...]Stop asking for 14 volts at idle - it isn't going to happen. The charging system requires the car to be at RPM's higher than idle to charge correctly. When you start draining batteries in normal everyday driving, then you need to take a look at your charging system. Exactly. In fact, if charging was 14 volts at idle, it would probably be excessive at higher speeds, vastly shortening the battery life. Before cars had alternators (okay, I'm showing my age now ), DC generators were used and nobody expected any significant charging at idle, even with a very low load. When alternators were introduced, the claim was that they would keep the battery fully charged even under idle conditions. That turned out to not be completely true; with heavy loads, idling sometimes isn't sufficient. In fact, for vehicles that typically idle a lot (taxis, police, etc., especially in cities with heavy traffic), they have "heavy duty" charging systems that output more at low engine RPM to handle the problem. However, most of us don't sit for long periods with the engine at 600-700 RPM (500 is indeed too low) and all the accessories on, but probably run at least an average of 1500 much of the time, and often 2500 (yeah, I know some of you can claim yet higher numbers ); that's easily enough to keep the battery well-charged if the alternator is doing the job. Link to comment Share on other sites More sharing options...
ericem Posted July 12, 2007 Author Share Posted July 12, 2007 not asking for 14v. I don't thing 11.7v at 2-3000rpm is normal. The max it would get up to is 12.4v at 4000rpm. Link to comment Share on other sites More sharing options...
Cougar Posted July 12, 2007 Share Posted July 12, 2007 The voltages at the RPMs you stated are low and probably means some of the diodes in the alternator are damaged. When the engine is running around 1,200 RPM you should see around 13 volts at the battery. Link to comment Share on other sites More sharing options...
nipper Posted July 12, 2007 Share Posted July 12, 2007 some reading http://www.autohausaz.com/html/auto_electrical_systems.html http://www.alternatorparts.com/understanding_alternators.htm Link to comment Share on other sites More sharing options...
ericem Posted July 12, 2007 Author Share Posted July 12, 2007 Ha, you wouldn't believe this. My belt wasn't tensioned enough, from what it seems because when i got rid of the play in the belt. my voltage could hold 13.5v whether i turned on ac and wiper and light all at once. Guess thats fine?? Just to make sure im going to see if the cells are full. If there not ill get some distilled water. Warrenty is only 1 year i found out and its 1 year and 1 month old. Link to comment Share on other sites More sharing options...
Cougar Posted July 12, 2007 Share Posted July 12, 2007 I thought about a loose belt but then figured you wouldn't let that happen. Link to comment Share on other sites More sharing options...
nipper Posted July 12, 2007 Share Posted July 12, 2007 Ha, you wouldn't believe this. My belt wasn't tensioned enough, from what it seems because when i got rid of the play in the belt. my voltage could hold 13.5v whether i turned on ac and wiper and light all at once. Guess thats fine?? Just to make sure im going to see if the cells are full. If there not ill get some distilled water. Warrenty is only 1 year i found out and its 1 year and 1 month old. No biscuit for you... (glad it was something simple) nipper Link to comment Share on other sites More sharing options...
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