Hello,
I have a 99 RX300 and the other day my wife went into town and was unable to turn over the engine to come home. I was able to jump the car and get her home. I have since charged the battery, but the following day it would not turn over again. It is close...but lacks a the extra umph needed. Today I pulled the negative cable and ran a voltage tester between the negative battery terminal and the negative cable.

What I found is that with everything off there seems to be a short of around 11 volts and about 0.5-0.7 amps. When I test the voltage between the cable and terminal I don't hear anything but when I test the amperage I hear some clicking and moving around on the other side of the firewall. My first guess is one or more of the servos possibly resetting itself under dash.

I then clipped the voltage tester in place between the cable and terminal and began to pull each fuse. I managed to pull all the fuses (including the slightly larger ones to the left) and did not notice a drop off at all in the voltage. There are a just a few large relays I have not pulled and will try later after the rain stops.

Here is my question. Considering the the voltage being read is continuous even with all the fuses pulled...could this be a bad battery?

Or, am I missing something. I've seen and ready plenty of threads on this site...but electrical problems don't seem to be common.

Any help would be appreciated for ideas on what the problem could be or perhaps other methods of testing.

Thanks

 

Top off the battery and have it tested.

 

Please look up 'parasitic draw' in RX300. In summary RX draws current at all times.

How old is the battery and what was its warranty? Depending upon your climate and battery quality you can expect 3-5yrs of life.on the average.

Just get a jump start and drive out to car part store and have the battery tested under load and they can check your charging system. You can buy a new battery right there.

Salim

PS: If you think the battery is already low, charge it overnight ... [auto shops would do that for you, but you will have to leave the battery with them].

 

I think if someone knows how to jump a car and use a voltage tester, that they won't have to pay an auto shop to charge their battery.

 

I live in Hawaii and the stamp on the battery states 2010, so I guess it's pushing the end of its life. I've been charging it overnight and I'll be sure to take it in today.

The only reason I pointed the cause of the possible short to my self is because I had just recently done some work on the dome light. The light would work for a bit and then cease to work until I moved the bulb around. Then it would work again for a short period of time and go out again. I decided to lightly scrape the contacts with sand paper and then put a bit of dielectric grease on them to prevent them from getting a buildup of moisture (very often happens here in Hawaii).

Any chance what I did would cause a possible short in anyone's view?

 

I had the battery checked and it passed. I decided to completely disengage the dome light and see what happens. So far so good. I'll keep updating.

 

mine will drain my battery and not crank the car if it sits for 2 days. I tried to locate the drain source but didnt have enough info in the manual for me to continue to isolate the main drain so i stopped looking.

 

My 1999 RX300 is a "spare" car now. I frequently leave it a month without use. Don't have a problem with the battery discharging, suggesting that an RX300 with no electrical issues doesn't discharge over this time period. Sounds like you have some faulty equipment that is discharging the battery that isn't on a fused circuit - 1/2 amp is a heck of a draw! Short in the starter?

 

After looking at other posts again on this subject I noticed that people were looking at the amperage drops as they removed each fuse...not the voltage. I again removed the negative cable, hooked my voltage tester inline between the battery post and the cable. Following this process I quickly identified a roughly 0.2-0.25 (200-250ma) drop in the amperage I was reading. Then I checked the source of the fuse and it was the ECU. I would expect this is normal. As I moved on I found another and this time it was a drop of roughly 500-550ma. Checked the source and Wala.....the proverbial Dome Light Fuse. I checked the rest with no noticeable change.

So here is my question...what should I be looking to check in this dome light circuit?

Also, this vehicle on multiple occasions has sat for 1-3 months and I've had no issues with it not starting. Just wanted to mention that.

 

Dome ( Courtesy light) stays on for a while after door is closed shut.

Salim

 

I removed my dome light mechanism a few days ago. Removed it to try and isolate a potential problem. I've read many of the posts on here including your parasitic draw thread.

Are the door locks by chance on the dome circuit (fuse 14)?

 

Some time back some one shared the wiring diagram. I dont have access to it. Sorry cant help you there, other than the sharing what I know.

Salim

 

I've always been told that it's the amperage and not the voltage that matters when trying to figure out a short (draw) on the battery. Today though I spoke with some guys at a parts place and that made it sound like the voltage is one of the factors they use.

When I described that my draw is around 11 volts (and also around 500ma) they seemed shocked at the 11 volts. I noticed this voltage did not drop even after removing all the fuses in the engine compartment. I plan on doing the fuses in the car later.

Does the voltage matter? Has anyone else noticed that if you run a tester between the negative cable to negative post that you get a similar amount of a voltage draw?

 

PM me an email address. I will forward you a bunch of info that will help.

 

Just wanted to provide an update.

I left for a Christmas break with the belief my battery was old but in ok condition...and that I had a short. Shortly after returning (and with the battery disconnected) the battery began to fail and since replacing it there have been no issues with power running out.

I guess it turned out to be the battery after all.