Studiogeek

iTrader: (6)

Hi,
I have an issue with my 95' SC400. When I have most accessories on (lights, wipers, radio/amp, blower, brake lights drawing power and in Drive, my aftermarket digital volt meter reads as low as 11v. If I also pull up to a light in drive (adds brake lights as well), the electronic parts show signs of low voltage such as dim lights, slower blower, radio cuts off and the car stalls (occasionally). It seems like the idle drops way down then the car cuts off (but starts right up again). This has only happened a few times but that is mainly because raising the idle keeps the car running so when I pull up to a light, I put the car in neutral and raise the idle a bit. The car also is less susceptible to the cut-off if I have the AC compressor on (raises the idle enough to help the car stay on). The heater blower on high seems to do the most damage. The first time it happened, it was right after I turned the blower on high while everything else was on. I could hear the blower slow down as the car died.
I have changed the alternator 3 times, put in a new battery, replaced the hydraulic belt tensioner so far, and it got better, but it still is an issue under load.
The aftermarket voltmeter reads as low as 11v under load when stopping or stopped (in the red) and around 12.5 to 13.7 or so when driving with average load. When it gets close to 11v, it may cut off.
Is this just my charging system or is it tied to my idle as well? Could a dirty idle control valve cause this? Could it be my idle reducing my voltage or my voltage reducing my idle?
Shifting into neutral at every light and revving it a bit is driving me crazy and makes everyone think I want to race ;-)

What could cause this?

(voltmeter I'm using below)

scENFORCER

I had this same issue (did the whole revving at a red light to stay running too lol) and I ended up replacing the alternator AND battery before the issue was solved. It is strange that you're still expieriencing a voltage drop after replacing those too. You could have some bad grounds, I did the big-3 ground upgrade and had no issues after that.

Studiogeek

iTrader: (6)

Yep, it's a real pain.
What is the big 3 ground upgrade?
Is there a DIY link?

scENFORCER

Its making sure your engine/battery/alternator are properly grounded to the chassis. Its primarily used for better electronics function when your system is being stressed due to a high output audio system. But my audio guy said that most cars (even new ones) arent properly grounded, especially older cars with aging wires and contact points.
I cant say it will fix your issue, but its an easy procedure I do to all my cars regardless. I say research it a bit more to see if it will have any affect on your issue.

Here's a link to get you started..
http://www.the12volt.com/installbay/...TID~73496~PN~1

Bains530

im having the same issue, cleaned the throttle body helped a little

Studiogeek

iTrader: (6)

Thank You! I'd bet this will help. I'm on it!
I will look into that as well. Thank You!

Studiogeek

iTrader: (6)

I bit the bullet and took it to Lexus for 27 point diagnostics. I never did that and I hope it is worth it.
I will find someone to perform the "Big Three" afterwards (unless Lexus does it for a reasonable price).
I will report back on the results soon.

Studiogeek

iTrader: (6)

Lexus screwed me (what a surprise).
They tried to charge $250 for a 27 point diagnosis. They barely checked anything. Things I know are wrong were not mentioned and there was no sheet outlining the 27 points and results. They just listed three obvious, unrelated expensive repairs and said we need to do those first, than we could look for the issue if that does not solve it. They are more of a ripoff than I imagined.
Total waste of money.
I am going to try the "big three" grounds this week or next week.

I'm open to all ideas. Keep them coming please.

Thanks to all!

megamax

iTrader: (9)

waiting on your results!!!

Studiogeek

iTrader: (6)

Another data point!
When I have the AC compressor on, the problem pretty much disappears. I know that raises the idle, what do you think the problem is?

Could it be my IAC valve?

Joey-E

iTrader: (1)

Well it wont hurt to try and its good place to start, clean it and see if it helps.

Sounds electric tho, i would definitely check your grounds like previously mentioned.

Studiogeek

iTrader: (6)

Thanks Joey!

I'm on that this weekend.

Hatchy400

I posted some things to check in this post:
https://www.clublexus.com/forums/sc-...ker-is-on.html
Hope it helps!

jjpark712

iTrader: (1)

If you have digital multimeter, check continuity and ohm between battery negative to chassis ground should b near 0.2 ohm. If it's good, now check how much voltage is coming out from behind the alternator( big wire that is held down with a nut) should see high 13v to low 14v.
If you see 13 to 14v, then your wires have too much resistance causing voltage drop.
If you don't see good charging voltage, you probably have faulty alternator.
Make sure you have no power steering leak which is right on top of alternator. It can cause alternator to short out.

Also what alternator are you running on the car??
I highly recommend denso if you are not using one already.
I have seen faulty alternator right out from the box many times.
Not a single bad one from denso.
Hope this helps.

Studiogeek

iTrader: (6)

I appreciate the link. I learned some things.
Thank You!
I'm going to a shop monday (it's cold/snowing here) to have them sort this out. I will print this out and give it to them. I don't know what brand the alternator is, a shop put it in when my other one died. Do you suggest a higher output alternator? Does denso make one? I do have a medium sized amp in the trunk pulling power.
Thank You!
Ok, willdo. I will have these messages with me when I go to the shop.
Thank You!