How to find slow electrical drain?

[jibbby]

I have a slow electrical drain in my Sc400 which actually kills my battery in two days time... No dash and or cabin lights are on, nothing visual from what I can tell...

So what is the most effective way to hunt down this electrical problem? I really don't know where to start?

 

[cribbj]

Jibbby, either befriend a good automotive electrician, or invest in a clamp-on DC ammeter and learn how to use it. Note, it must be a clampon ammeter that can read DC amperes, not just AC amperes.

With the engine off, put the clamp-on ammeter on every circuit leaving your fuse box until you find the one that shows some current flow. That's your culprit. Then just figure out what's on that circuit and why it's using current without the engine running.

The circuits with the highest probablility of failure will be the ones you or someone else have modified in the past. OEM wiring doesn't fail that often.

If you don't find any leaky circuits leaving the fusebox, then have a look at your alternator and/or the starter circuit.

 

[jibbby]

Thanks John, that's exactly what I was thinking... I have also used a DC ammeter in the past but just wasn't 100% sure if the fuse box was the best place to start...

I will give it a go this weekend and see what I find...

 

[stevechumo]

I actually think it's a bad battery that doesn't keep the charge. It happened to me several times. However, my situation lasted up to 3-4 days or a week. It's not easy to troubleshoot the battery if that happened. When I charged the battery full, it worked great. If I left the car for 3 days, it didn't have enough voltage to start the car. It read about 9-10 volts. It happened like that several times.

I then charged the battery full, drove continuously for a couple hours, took the battery out to Autozone (that's where I bought it from), they ran a test through a big battery tester and said it's good. I tried to tell them it doesn't keep the charge and they didn't believe me. I thought "what the heck? Of course it showed full voltage now because I just drove it." I then left the car for a week, the voltage dropped to 9-10 volts. I took the battery back to Autozone. They ran a test through it and said it's bad. They replaced it. LOL.

 

[jibbby]

Well, it turned out to be a bad starter motor after all...

What was happening is I would get slow starts or turnover when the car was cold the next day which lead me to believe the car was starting with a very weak battery charge......I thought it was an electrical drain for sure.. Turns out it is the starter motor... The starter motor will begin turning fast then when first engaged then begin to slow down... The motor barely turns over fast enough to start the car when completely cold.. It almost feels like a compression freeze starting occure, but I am confident it is the starter.. The battery remains fully charged as I did test when cold... It's very strange as the starter motor I would think would stop completely and not start to slow down if faulty...Weird.....

I jumped to a conclusion before really testing and diagnosing the problem..Sorry fellas and thanks for the replys...

Anyway, off with the intake, big job ahead... Damn!!!!

 

[stevechumo]

It's a PITA. Trust me on that. Once you do it and if you plan on keeping the car, you may replace all seals & gaskets at once. A set of specific swivel 12mm & 14mm sockets will help you a lot. They can be found at Sears and special tool shops. A universal socket won't help as much as the specific ones. Good luck!

 

[jibbby]

Thanks Steve, I know it's a big job... I don't know why Lexus/Toyota engineers located that starter in the middle of the motor?????

Not Cool!!!!!!:thumbsdown: :17:

 

[stevechumo]

Thanks Steve, I know it's a big job... I don't know why Lexus/Toyota engineers located that starter in the middle of the motor?????

Not Cool!!!!!!:thumbsdown: :17:

I know Toyota have top notch engineers, but I think it's a bad design for that starter location. The starter could have been relocated near the engine's bottom that meets with the tranny. Another bad thing is the main engine wiring harness that's nearly right above the starter. It's a pain in the butt to lift it up so the water bridge can be taken off. Then the heads can be removed. The SC has tighter space than the LS and it couldn't be done without removing the engine. You'll see what I mean.

 

[jibbby]

Well, the starter motor is still turning for me right now but slow, so I will ride it a little bit longer... Steve, did I read your post right? Did you say you have to remove the engine to change out the starter motor? I was aware of only removing the intake and related stuff on top of the engine... If I gotta remove the engine, I may have to run her off the cliff and collect the insurance money instead...:deal:

 

[stevechumo]

Sorry for the confusion, John. I meant to remove the heads, I had to remove the engine. You can remove the starter without removing the engine. If you can't put your hand down there (basically there's not enough room), get some right tools that can help you rather than trying to spend hours on it.

 

[john86]

It probably isn't a slow drain, it is just an ineffective charging system. Biggest problem with low output on these bikes is that the rotors go bad. Check the resistance values on the slip rings COLD and then HOT and you will often find that they go out of range when the engine warms up. Occasionally the rotors will shear the key and are actually spinning on the end of the crankshaft, but that is rare. Usually the biggest problem is getting them off the crankshaft. Be sure to use the correct special tool for removal. You can pull lighting fuses to isolate the charging system output, to ensure that the problem is output and not a draw, but there isn't much in the system to draw down the charging system other than the halogen headlight and running lights.