CyFi6

Well the RX300 battery tends to die when left unused for several days. I went in and did a parasitic drain test. I found total draw to be around 500 to 600 mA. General rule of thumb specs are 50mA maximum. When pulling the ECU fuse, the draw drops by about 300mA, and when pulling the dome fuse, the draw drops by about 200 to 300 mA. With both fuses pulled, total draw is less than 5mA.

My question is what can I do to further find my draw? I don't have access to any wiring diagrams, so I am not sure exactly what components draw power from each of these two fuses. All accessories were completely off during the test, and all the roof dome lights, key ring lights, and front door foot lights were off during the test. Any help narrowing down the issue would be great!

salimshah

With all the electronics and 'auto' modes the RX will draw about 250ma-350ma.

Without taking any fuse out after double lock action on the remote, measure the current draw and see it drop over time. Assuming your dome lights are turned off you will see the current drop to the above mentioned number.

If you want the number to be less, turn off the auto modes (auto- headlight on etc).

A good battery should be able to sustain the draw for a week or two and quickly recover on getting recharged.

My first suspects for stand bye draw are the dome lights and add on accessories.

Salim

bob2200

Another suspect is the battery. The battery capacity should be hundreds of amp-hours and a draw of 500mA is only 12 amp-hours/day.

AngNKY

I need to do a Parasitic Draw test on my 1999 RX300.
I have done the reseach and think I know how to do it, but I don't know how to test the fuses INSIDE the car.
As I understand, I need to get the car to go to "sleep" to do the test.
In order to get the car to go to "sleep", I need to close the doors and let it sit for while - untouched.

So, how do I get into the car to pull the fuses in the car.
I thought that I could just sit in the car for a while, but the fuses will be difficult to pull out from inside the car. Ideally, I would kneal outside the car with the door open - which would prevent the car from going to "Sleep".
There is no "button" to press to trick the car into thinking that the door is closed.

Any advice for my quandry?
Thanks.
~ Angela

salimshah

I understand what you are trying to do, but the same can be achieved by making 2 current measurements ... once with the fuses and the next time without the fuses. You will have to wait couple of minutes to allow RX to sleep.

Salim

AngNKY

Sorry, Salim.
I do not understand your response.
There are about 30 fuses inside the car.
Are you suggesting that I pull all the fuses at once?
I believe that I will need to test each fuse.

I was looking for a way to trick the door into thinking that it was closed.
I pondered finding the fuse that deals with door and pulling it - but I didn't know if that work.

Will I have to pull a fuse, close the door, wait a few minutes for the car to go to "sleep" and then test the pull on the battery?
That will take a while.
How long do I need to wait for the car to go "asleep"?

salimshah

And I thought that I understood what you were trying to do (just want to see the current after pulling out a fuse or two.

For static loads (not affected by sleep) can me measured at any time.

The door catch has the door lock actuator and as the hook moves in the catch-levers grab it and inside the actuator things turn and throw the switch that indicated the door is close. If you want to trick it, you have turn catch as if it is going over the hook. The system has double lock (like first catch and second catch ... partially closed door and fully closed door). making the door think it is open can be tricky as you have to release the door and ensure the catches (over the missing hook) mimic the door opening.

Last time I checked on my RX it was close to 3 min for the RX to enter sleep mode.

Salim

code58

Angela,
Salim is correct. You can "fool" the system to think the door is closed by closing the latch (close it all the way to the second click). I do it by using a Philips screw driver in the latch to do the same thing the latch striker does in latching. Remember to wait a few minutes for that system to go to sleep. When you are done with your testing, be sure to use the same philips to pull the latch halves back open while releasing the door handle, either inside or outside. I have never tested the parasitic draw on an RX when "asleep" but the 250- 350MA that Salim noted seems a little high to me. I have 4 amp clamps and was used to testing amp draw in the work I did but don't ever remember anything with stock equipment testing that high.

AngNKY

Thanks, Guys for your advice regarding tricking the door into being closed.

I did the parasitic draw test and had the EXACT SAME RESULTS AS POST #1 above.

I have verified that all lights are off - at least the bulbs that are still working (my glove box light and foot lights have not worked for a long time).

Two weeks ago, I returned home from a month long trip and the car started fine.
Then this past Sunday, the battery started draining in less than 24 hours.

Before I started the test, I test the battery and it had 12.2 Volts - which I thought was good, but after the test, the car would not start. I have had a small parasitic draw on the car since I got it. The battery would drain after 2 weeks. But after reading some threads on here, that seems normal.

I am trying to sell the car, but cannot in this condition.

Where do I go from here?

Can anyone direct me to wiring diagrams for the ECU-B and DOME fuses?

Thanks,
~ Angela
(a stubborn Lexus owner who is tired of taking her car to the dealer just to be told they don't know what is wrong. I'm trying to figure things out myself - or at least understand it better.)




ps: In case it matters, this car has other issues with codes which may be electrical in nature: mainly p0171 "too lean" errors, but also 1133 Air Fuel Sensor Circuit Response Malfunction (Bank 1 Sensor 1); 0450 Evaporative Emission System Pressure Sensor / Switch; 0446 Evaporative Emission System Vent Control Circuit; my ECT does not seem to get over 190 degrees (I think it is supposed over 190); 0125 Insufficient Coolant Temp for Closed Loop Fuel Control (this error is rare).
I purchased a code reader and I clear this codes as they occur (after taking pics of them and the data). I hate driving around with my car acting horribly. I clear the code and it runs smoothly again. It seems to act up when the engine is wet and stops after 15 minutes or so when the engine dries out (which would indicate an electrical issue). Also, filling the fuel tank seems to stop the "too lean" errors.

I will address these issue when I get my battery to last more than a day, but I thought it might be helpful to someone here.

salimshah

So how old is the battery?

Also what type, low maint (oem), or deep cycle (opima)?

if the battery has never fallen below 10v, have you tried charging it [24hrs for low maint and 48hrs for deep cycle @ right charger settings]. If you dont have a charger, auto shops would do it for free [they do not charge overnight ... so drop off early morning and pick up the next day late in the afternoon]. They will also perform load testing for you.

You did not mention if RX can be started with a jump. If so then it is a problem with the battery.

Since you are handy with a VOM, I would not mention terminals and clamps.

Since your parasitic draw is in the 'expected' range, I would buy a new battery (specially if it is 3+yrs), else try the warranty). I tell you it is not worth the aggravation.

Does your door ajar dash indicator light up when you open the door? This will help you diagnose the courtesy light issue.

Salim

AngNKY

Salim,
Thank you so much for your insight and time in helping me with this issue.

Please have more patience and answer some basic questions for the curious novice.

4 years (today)

unknown. It is a Lexus battery. (sorry, it is cold out there! :-) )


Yes, it can be started with a jump.
Are you saying that if there is a parasitic draw on the battery draining it overnight the car would not be able to jumped to get it started?

What would you say about terminals and clamps if I were not familiar with Voltage Meter?

I plan to buy a new battery today (today is the last day of year 4, so tomorrow the battery will more expensive), but am still concerned about a short.

Yes, my Door Ajar indicator does come on. What does that tell you about my courtesy lights?

New Question:
I read that if you take the leads off the battery and perform an Ohms test on the leads and the meter shows no resistence (0), then there is a direct short in the system. This did occur for me.

Do you agree with this Ohms / short test?

THANKS!
~ Ang

salimshah

In an ideal world the lead acid batteries being rechargeable (chem <=>electrical), but the reality is that overtime they deteriorate and eventually can not sustain the specified current draw [such as 510cca]. It can be verified by having the battery fully charged and then subjecting it to load test. If your battery is old it may pass the test marginally ... one week of no-charge and it will fail to start your RX.

When you jump start the RX the, auxiliary battery provides the current your battery fails to produce. If you had a real short, you would get huge current draw from the aux battery and you would fail to start your RX.

Based on your parasitic draw, which seems to be in line with posted numbers, I feel confidant that you do not have a short. The other test you can do is check if the discharge light is not on when the engine is running [lights on and brake pressed] ,,, this would atleast tell you that the alternator is supporting all the drawn current still is able to charge the battery.


The place that sells the battery can do the standard checking for you.

I would say lets take those baby steps, before we look at other problems.

ps: Examine the terminals and clamps to see the posts are secure and the connections are free of effervescence.

Salim

Your real load R=Battery-voltage_in_volts/current_in_amps
Your current_in_amps (is the current you measured in various stages ... parasitic draw.
The VOM meter OHM scale works for fixed resistances .... not for fillament (lamp) or motors (coil) or relays.

angkorthom

I have to perform the same test, i took it to an electrical guy and he said there is a 180 miliamp draw on mines. I know my battery is going bad as well because it won't last two days without driving it. The battery is bad because it would drain it down and i'll get it jumped and then i'll let it sit and drains again. I did this for about a year and i guess that screwed up the battery. I need to know where the source of the draw is so i will have to do the fuse pulling trick. I think its somewhere in the doors because i might have shorted something because the windows don't' work now when rolling it up or down on the individual switch. it only works on the main master switch i can control all windows. Any suggestions?

salimshah

Your parasitic draw is low [nothing wrong with it ... although you may like to check it again with a fully charged battery and you may see it get a bit higher and rise to what others see].

I would not chase this ghost.

Salim

angkorthom

Well its causing the battery to drain, i plan on getting a new battery to see if it does the same thing which i'm pretty sure it would. I tapped into the wrong wires when trying to install the front passenger after market door lock actuators but now i have removed it and put in OEM ones and the door works fine but it drains my battery and windows don't work. I know this is a difficult fix because i am chasing a ghost but what else can i do? i need a ghost buster..............