OneGuyInCA Posted November 15, 2004 Share Posted November 15, 2004 Hello. My wife's car (1999 RX300) starts but goes dead after it starts which leads me to believe the battery may be suspect. It only does so every so often. So I did a meter check. The battery is registering about 12.3volts. With the engine on (when I do get it to start), the reading is 14volts (What the alternator puts out). I don't have an owners manual nor do I have the repair manual to check but here are my questions? 1) What SHOULD be the voltage reading for the battery with the engine UNSTARTED? 2) What SHOULD be the voltage reading for the battery with the engine STARTED? 3) If I disconnect the batter to replace it with a new one, will there be some recoding (keys, stereo, etc) that needs to be done? Can someone help please? Thanks! Quote Link to comment Share on other sites More sharing options...
bugman72 Posted November 15, 2004 Share Posted November 15, 2004 i just put a new battery in my 1999 and everything worked fine , even after being disconnected for about 20 min. i was also worried about my radio but was told this year rx300 does not code radio. just had to reset clock and radio stations. Quote Link to comment Share on other sites More sharing options...
bartkat Posted November 15, 2004 Share Posted November 15, 2004 You can get the battery tested. Could be the alternator isn't charging it. Not sure on your specific car, but the indicator on the dash should read about 13 volte, engine running or not. Quote Link to comment Share on other sites More sharing options...
riwyle Posted November 15, 2004 Share Posted November 15, 2004 Unless tested under load, the voltage read on a battery is pretty meaningless. Will tell you if you have a dead cell, but not if the battery has high internal resistance. If the battery has enough energy to crank the engine, I do not see how it could not be able to supply the lesser current needed to fire the plugs during the short time it takes for the engine to reach enough speed for the alternator to take over. I would look for other causes . Quote Link to comment Share on other sites More sharing options...
SKperformance Posted November 15, 2004 Share Posted November 15, 2004 lol i don;t think it is your battery i seem to keep answering posts with iacv check it out. Quote Link to comment Share on other sites More sharing options...
OneGuyInCA Posted November 15, 2004 Author Share Posted November 15, 2004 loli don;t think it is your battery i seem to keep answering posts with iacv check it out. ← So the Idle Air Control Valve... hmm... seems possible. SK or anyone... where is the IACV on the 99 Lexus RX300?? And what should I use to clean it with? Easy to get to hopefully? If anyone has a pic of this control valve of the RX300... that would be great! If not... I can volunteer to take pictures when I get to it on my wifes car. But I need to know what I'm looking for first! HELP... anyone? Quote Link to comment Share on other sites More sharing options...
SKperformance Posted November 15, 2004 Share Posted November 15, 2004 your engien is the same as an es search in that section someone did post pics a while back Quote Link to comment Share on other sites More sharing options...
ColinBarber Posted November 15, 2004 Share Posted November 15, 2004 Have a look at this thread for the location http://us.lexusownersclub.com/forums/index...ic=7408&hl=iacv Quote Link to comment Share on other sites More sharing options...
SKperformance Posted November 15, 2004 Share Posted November 15, 2004 well done Quote Link to comment Share on other sites More sharing options...
artinist Posted November 22, 2004 Share Posted November 22, 2004 a quick way to check the alternator is to: 1. start the car 2. disconnect the battery 3. turn on the headlights 4. step on the brakes. if the car is still running, most likely the alternator is working just fine and its just the battery that is not taking charge so get a new battery Quote Link to comment Share on other sites More sharing options...
wwest Posted November 24, 2004 Share Posted November 24, 2004 "Disconnect the battery........" NO! NEVER! NOT! With the battery disconnected with the engine running the alternator voltage output may be so excessive that some of the electronic components may vaporize...REALLY. The battery "load" charged or not, is a part of the design parameters of the alternator battery charging control circuitry. Additionally, checking the battery voltage, within a certain range, is somewhat meaningless. The charging circuits are designed to provide a different battery voltage charge level as a function of prevalent ambiant temperature. Battery charging voltage will typcially be higher, ~2 volts, during cold weather than in summer. Anytime you suspect battery problems the very first thing to do is remove the connections from the battery posts, clean and burnish, w/wire brush, the posts and the connection surfaces, reinstall and carefully tighten. Quote Link to comment Share on other sites More sharing options...
RX400h Posted November 24, 2004 Share Posted November 24, 2004 "Disconnect the battery........"NO! NEVER! NOT! With the battery disconnected with the engine running the alternator voltage output may be so excessive that some of the electronic components may vaporize...REALLY. The battery "load" charged or not, is a part of the design parameters of the alternator battery charging control circuitry. Additionally, checking the battery voltage, within a certain range, is somewhat meaningless. The charging circuits are designed to provide a different battery voltage charge level as a function of prevalent ambiant temperature. Battery charging voltage will typcially be higher, ~2 volts, during cold weather than in summer. Anytime you suspect battery problems the very first thing to do is remove the connections from the battery posts, clean and burnish, w/wire brush, the posts and the connection surfaces, reinstall and carefully tighten. ← I agree with Double Dubya on this one. The battery disconnect test was effective many, many years ago when there were separate voltage regulators in the engine bay. Performing this test on a modern-day vehicle could very well fry electronics - DO NOT DO IT! If an engine is started easily and then suddenly dies, chances are that the culprit is NOT the battery. If the engine can be started right back up again, then the alternator is not the culprit either. Quote Link to comment Share on other sites More sharing options...
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