x24paul

My wife's rx300 has been running well, no problems. Today, we ran all over town, at 4 p.m. and 98 degrees the truck would not start. Battery is fully charged, even tried another one. No juice is flowing, the dome light is lit, but barely, nothing has power and it won't start.

4TehNguyen

iTrader: (1)

how do you know its fully charged, just because a battery has 12V on it and lights up lights doesnt mean it can crank a car. How old is the battery?

x24paul

My son can out and we swapped batteries after we could not jump it. The one year old battery was then taken to AutoZone and tested. Pretty sure it's not the battery.

geko29

how are the terminals on the battery cable? Make sure they're clean and tight. Also check where they attach to the cable. It sounds like you have a loose/weak connection, possibly to ground.

If you're handy with a multimeter, here's a couple of quick tests you could do:

In VDC mode: Red probe on the POSITIVE battery cable, Black probe on the engine block or an unpainted body part (bolt, etc). Should show > 14V
In Impedance/continuity mode: either probe on the NEGATIVE battery post on the battery, other probe on the engine block or unpainted body part. Should show very close to zero Ohms.

If you use the positive terminal for the second test, your meter will explode, so please be careful--re-cover the terminal before doing this one.

bitkahuna

iTrader: (20)

what year is your rx300 and it wouldn't start even after swapping out the battery?
edit: from profile see it's 2001

also: moving this to rx forum for more ideas, thx.

GSteg

iTrader: (15)

SInce the engine is not running, I doubt he'll see 14V. Maybe 12.5V with the battery resting. But yea, I would check cables and terminal first before anything else.

geko29

You're absolutely right. It's been awhile since I've actually tested a battery for voltage, as opposed to an alternator (where you do want 14V). Anything between 12.1 and 12.8 with the engine off is usually indicative of a healthy battery.

x24paul

Ok, just finished the tests. Ground is ok, losing power from positive side. Battery is at 12v. Red probe on battery, black on body, 6v.

x24paul

Could it be the starter, is it possible the starter is in "load" position. Very weak lights, no power for anything but dim dome and door lights. Had this happen on Chevy truck once.

thomas1

Could very well have a set of shorted starter contacts. However it would drain the battery down pretty quick. By the way car running the voltage should be 13.4 to 14.1 volts. The battery with engine off is 12.5 to 12.6volts.
You say the ground is good, so you read 0 ohms between the negative and engine block? I would unhook the starter positive lead and safely tape it off and then turn the ignition on to see if the lights are right in the car. If they are you have a bad starter. the auto store will test it for free also if you drag it down there.

x24paul

It is the ignition switch, there is a short in the switch. Thank you all for the suggestions. I had the same problem in a 74 Impala, but it at least gave me a little advanced warning. These damn Lexus, they just go bad. Had a transmission just quit working when I stopped at a red light. $3400.00 later I am back on the road, other than that it's a great ride, only reason I am not getting rid of it.

Thanks again guys, I appreciate all the time and effort you guys put into helping, not just me, all us non mechanic types.

JAB

Did you replace the ignition switch yourself, or pay someone to do it? If the former, any pointers on how to do; if the latter, how much you pay? Thanks.