Electrix Probelem Please Help (ALT?)
09-28-06, 07:18 AM
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Electrix Probelem Please Help (ALT?)
First Off my car is bone stock with sylvania silverstars as my only mod.
i've got 130k on a 95 sc300 red on black 5spd. my battery is one year old but for some reason i'm getting a very powerful power drain when my brakes are applied. radio momentarily cuts off lights dim then brighten again. symptoms seem to be getting worse. now, with lights on and signalling same momentary drain. what do you all think could be the culprit ?
my guess is the alternator but was wondering if these are common symptoms. with my mileage i'm assuming the power steering leak the previous owner fixed now is affecting this type of draw.
any help is greatly appreciated.
vince
i've got 130k on a 95 sc300 red on black 5spd. my battery is one year old but for some reason i'm getting a very powerful power drain when my brakes are applied. radio momentarily cuts off lights dim then brighten again. symptoms seem to be getting worse. now, with lights on and signalling same momentary drain. what do you all think could be the culprit ?
my guess is the alternator but was wondering if these are common symptoms. with my mileage i'm assuming the power steering leak the previous owner fixed now is affecting this type of draw.
any help is greatly appreciated.
vince
09-28-06, 08:59 AM
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ground
The ground suggestion is the answer.
Is it only your brakes? Switching on the headlights doesn't lower the voltage? How about working the power seats? If it is only your brake lights that do this you are screwed. To me this means that you are no longer wired in accord with the schematic. You don't sound savy enuf to troubleshoot that and I mean no insult. The risk is that you will insert more problems, also.
Take it to an electrical shop.
Harbor freight has "digital voltmeters" for $20. Everybody needs one anyway so get yours now. It has good instructions for simple measurements and will keep you from burning up the meter.
Follow the neg cable and it should lead down to the AC compressor. I think it is conneted to a bracket that is itself bolted to the AC comp mounting bolt. You need to check the connection between(btwn) the neg terminal of bat and the connector. Then the con btwn the cable and the bracket. Then the bracket to the bolt that goes into the block. All of this stuff has to be jelly jar lid tight and clean. The "words" in elec trical theory are "all connections must be MECHANICALL TIGHT and ELECTRICALLY COMPLETE". Dirty bat terminals can be tight as hell but not making contact as in electrically complete.
Bad grounds can cause mind boggling problems that defy electrical trouble shooting logic.
With the eng off and then again with the brake applied:
Measure the V across the bat terminals (not the connectors). It should measure 12.6Volts. Measure from the frame/body bolt to the positive terminal (not connector), 12.6V. From the body to the bat pos connector...12.6 From pos term to the ground bracket on AC. Same but to eng bolt. Same but to eng block. If you get less than the 12.6 volt measurement, you have found your bad ground connection. There is a strap from the engine to the frame that often deteriates and gives grounding problems.
I wish the very best of luck.
John
Is it only your brakes? Switching on the headlights doesn't lower the voltage? How about working the power seats? If it is only your brake lights that do this you are screwed. To me this means that you are no longer wired in accord with the schematic. You don't sound savy enuf to troubleshoot that and I mean no insult. The risk is that you will insert more problems, also.
Take it to an electrical shop.
Harbor freight has "digital voltmeters" for $20. Everybody needs one anyway so get yours now. It has good instructions for simple measurements and will keep you from burning up the meter.
Follow the neg cable and it should lead down to the AC compressor. I think it is conneted to a bracket that is itself bolted to the AC comp mounting bolt. You need to check the connection between(btwn) the neg terminal of bat and the connector. Then the con btwn the cable and the bracket. Then the bracket to the bolt that goes into the block. All of this stuff has to be jelly jar lid tight and clean. The "words" in elec trical theory are "all connections must be MECHANICALL TIGHT and ELECTRICALLY COMPLETE". Dirty bat terminals can be tight as hell but not making contact as in electrically complete.
Bad grounds can cause mind boggling problems that defy electrical trouble shooting logic.
With the eng off and then again with the brake applied:
Measure the V across the bat terminals (not the connectors). It should measure 12.6Volts. Measure from the frame/body bolt to the positive terminal (not connector), 12.6V. From the body to the bat pos connector...12.6 From pos term to the ground bracket on AC. Same but to eng bolt. Same but to eng block. If you get less than the 12.6 volt measurement, you have found your bad ground connection. There is a strap from the engine to the frame that often deteriates and gives grounding problems.
I wish the very best of luck.
John
09-28-06, 09:05 AM
#6
The ground suggestion is the answer.
Is it only your brakes? Switching on the headlights doesn't lower the voltage? How about working the power seats? If it is only your brake lights that do this you are screwed. To me this means that you are no longer wired in accord with the schematic. You don't sound savy enuf to troubleshoot that and I mean no insult. The risk is that you will insert more problems, also.
Take it to an electrical shop.
Harbor freight has "digital voltmeters" for $20. Everybody needs one anyway so get yours now. It has good instructions for simple measurements and will keep you from burning up the meter.
Follow the neg cable and it should lead down to the AC compressor. I think it is conneted to a bracket that is itself bolted to the AC comp mounting bolt. You need to check the connection between(btwn) the neg terminal of bat and the connector. Then the con btwn the cable and the bracket. Then the bracket to the bolt that goes into the block. All of this stuff has to be jelly jar lid tight and clean. The "words" in elec trical theory are "all connections must be MECHANICALL TIGHT and ELECTRICALLY COMPLETE". Dirty bat terminals can be tight as hell but not making contact as in electrically complete.
Bad grounds can cause mind boggling problems that defy electrical trouble shooting logic.
With the eng off and then again with the brake applied:
Measure the V across the bat terminals (not the connectors). It should measure 12.6Volts. Measure from the frame/body bolt to the positive terminal (not connector), 12.6V. From the body to the bat pos connector...12.6 From pos term to the ground bracket on AC. Same but to eng bolt. Same but to eng block. If you get less than the 12.6 volt measurement, you have found your bad ground connection. There is a strap from the engine to the frame that often deteriates and gives grounding problems.
I wish the very best of luck.
John
Is it only your brakes? Switching on the headlights doesn't lower the voltage? How about working the power seats? If it is only your brake lights that do this you are screwed. To me this means that you are no longer wired in accord with the schematic. You don't sound savy enuf to troubleshoot that and I mean no insult. The risk is that you will insert more problems, also.
Take it to an electrical shop.
Harbor freight has "digital voltmeters" for $20. Everybody needs one anyway so get yours now. It has good instructions for simple measurements and will keep you from burning up the meter.
Follow the neg cable and it should lead down to the AC compressor. I think it is conneted to a bracket that is itself bolted to the AC comp mounting bolt. You need to check the connection between(btwn) the neg terminal of bat and the connector. Then the con btwn the cable and the bracket. Then the bracket to the bolt that goes into the block. All of this stuff has to be jelly jar lid tight and clean. The "words" in elec trical theory are "all connections must be MECHANICALL TIGHT and ELECTRICALLY COMPLETE". Dirty bat terminals can be tight as hell but not making contact as in electrically complete.
Bad grounds can cause mind boggling problems that defy electrical trouble shooting logic.
With the eng off and then again with the brake applied:
Measure the V across the bat terminals (not the connectors). It should measure 12.6Volts. Measure from the frame/body bolt to the positive terminal (not connector), 12.6V. From the body to the bat pos connector...12.6 From pos term to the ground bracket on AC. Same but to eng bolt. Same but to eng block. If you get less than the 12.6 volt measurement, you have found your bad ground connection. There is a strap from the engine to the frame that often deteriates and gives grounding problems.
I wish the very best of luck.
John
Great post man - wish this was around 4 years ago when I had to replace the motor in my SC. I missed a ground somewhere and it was a PITA to find!
Jonny
09-28-06, 11:03 AM
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noticed this morning turn signal initiation has the same effect. the drain by the brake lights is far more potent. Is there a page in the factory service manual with the ground locations ? I didn't find one, just underhood parts location, and I didn't get the wiring diagram manual. i'll try following the main engine ground tonight and report back with findings.
my multimeter is FLUKE by brand. FYI. very useful helped me detect a short in my supra's cam position sensor that a shop could not find.
thanks for all your help. will have more questions tomorrow.
my multimeter is FLUKE by brand. FYI. very useful helped me detect a short in my supra's cam position sensor that a shop could not find.
thanks for all your help. will have more questions tomorrow.
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09-29-06, 06:59 AM
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update... removed main engine ground also the rear grounding strap, sanded contacting parts to bare metal reassembled. removed tailights replaced original bulbs checked contacts. pulled fuses, checked fasteners on main fuse box and interior fuse box. tested, same issue. what gives ? reviewed service manual for ECM stop light pin location and grounds am going this route this weekend. any other places I can check ? the car has never been wrecked or flooed and has barely even been stored outside it's entire life. what ground issues could there be ? I do live in a humid climate but should not degrade conductivity by this much.
All, I really love my car and much like you all, am everybit a perfectionist please add anything you may have to aid the cause.
thanks
All, I really love my car and much like you all, am everybit a perfectionist please add anything you may have to aid the cause.
thanks
09-29-06, 07:37 AM
#9
Lexus Champion
The Fluke is a superb meter ...
What are the voltage reading on the battery terminals... static with everything turned off, doors closed ?
The voltage reading with the engine idling only.
The voltage reading with the full electrical load, (A/C fan high, high beam headlamps on and brake depressed)
This will indicate the condition of your alternator.
What are the voltage reading on the battery terminals... static with everything turned off, doors closed ?
The voltage reading with the engine idling only.
The voltage reading with the full electrical load, (A/C fan high, high beam headlamps on and brake depressed)
This will indicate the condition of your alternator.
10-25-06, 07:47 PM
#12
retest. It should be >12v, 12.6 is a good #.
Back to the original Q: Vince 95
Negitive battery cable grounds to the body about 12" from the battery.
Then continues to the block. There's a small ground strap from the
firewall to the rear of the head (sc300). Also another strap from body
to left side bottom of the bellhousing.
Double check all the brake light bulbs for the proper part #.
A 1157, 2057, 2357 etc will all fit & operate, but the resistance
is different for each bulb.
Last edited by supra dr; 10-26-06 at 06:26 PM.
10-26-06, 09:13 AM
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battery is very strong, brand new Interstate. Actually the voltage is higher when car is off. Bulbs all look right. problem i have i when im sitting in rush hour traffic, with all accesories on and lights on, after a prolonged time, my radio will start to garble and turn off, lights will start to dim; as soon as i turn off something, like climate control, the radio comes right back in a matter of seconds. Really seemed like a charging issue to me, 125k on car, i wouldnt expect the alternator to last forever. Ive found some reman. alternators for $200ish, if anyone knows of a better deal let me know. Thanks.
11-24-06, 11:48 AM
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OK, i am starting to get pissed now, i changed the alternator, and my idiling voltage seems to be higher, but still with everything ON, sitting in gear idling, the voltage will drop way down, i let it sit and eventually it got down to <10V.
I need HELP!
I need HELP!
