grrrr 3 lights on dash?

macasdude · 10-06-2009, 01:54 AM

so while driving every time i hit a bump the 3 lights on my dash would come on Fan,Batt,ebrake light then when i hit another bump they would go off, when i turned blinkers on they would ocme on... well one day they stayed on while driving... after i parked the car all lights and stuff was out with car turned on, the next day my car wouldnt start! i jumped my car and it started but as soon as i turned on my headlights the car shut off.. Thinking it was my alternator i charged the batt, and checked my alternator one of the wires was loose so i tightend it and vola the lights were off.. i took the car to autozone and they said my alternator was good...

3 days later i hit a small bump and the same thing happes!! so i check the wire and its still tight?!!? thinking my batt is bad i take it to autozone and they say its bad so i get it replaced... the 3 lights are still on! so i have them check my alternator and they say its bad!?!? what can cause this? if i replace the alternator is it just goign to go bad again??

does the 3 lights meen a problem with alternator? need help thanx!!

1985 mr2 mk1
3sgte gen iii j-spec turbo engine swaped

had car for about 6 months and never had this problem.. had my fueltank swaped and the problem started a day later O.o

jimmer411 · 10-06-2009, 03:33 AM

3 lights is almost always alt.

PumpMag · 10-06-2009, 04:06 AM

The 3 lights on usually indicate the alternator going bad.

If your battery is more than 2 years old, I recommend replacing it also.

PumpMag · 10-06-2009, 04:11 AM

If you just bought a new battery and have trouble starting, a bad alternator would not sufficiently recharge it. Use a voltmeter to check if the new battery is below 12 volts.

muffinman · 10-06-2009, 10:06 AM

possibly a short in the alt which is why everytime you hit a bump it acted up but the 3 lights are always some sort of problem with the charging system.GL

macasdude · 10-07-2009, 10:44 AM

thanx getting the alt replaced today well see how it goes

tjmr2 · 10-11-2009, 10:05 PM

The three lights are all powered from different circuits (as in charge, cooling and brake) and can be activated in two ways. All three circuits use a diode in the circuit to control current flow (think of a diode as a valve that only allows current to flow in one direction).

When you pull your emergency brake for instance it closes the switch that grounds the brake light to the chassis. Same for the other two lights, when each circuit needs to show a problem it completes the circuit by grounding the light (they have constant voltage applied to one side of the bulb and the other side is switched to ground), seems backwards.

All three lights are tied together in only one place, and that is the L terminal on the alternator. (the 89 BGB shows it as the yellow wire) This wire connects the L terminal on
the alternator to the 5A charge fuse (in the fuse box by the battery) then to the three lights.

There must be more current & voltage applied through the charge fuse from terminal L on the alternator than is applied to the other side of the lights by the individual circuits to keep the lights from turning on. This is where the diode in each circuit comes into play. If all three lights are on they are using terminal L on the alternator as a ground.

To test all this:

1: Remove 5A charge fuse & turn on ignition.
a: Charge light should be off, brake and cooling should be on.
b: Using a meter check both terminals in the fuse block to ground, one should have 12v. Make note of which terminal has voltage.

2: Start car.
a: Charge light still off, brake and cooling off.
b: Using a test meter check both terminals of the charge fuse to ground, both should now show 12v. If only the terminal from step 1 has voltage you have a problem either with the alternator or wiring between the alternator and fuse block.

Can perform either steps 3 or 4 next.

3: Block up car and connect the meter between terminal L on the alternator and ground.
a: Start engine.
b: + 12v terminal L on alternator is good.
c: 0v Replace alternator.

4: With engine off test the resistance between terminal L on the alternator and the charge fuse. One side of the charge fuse should have almost 0 ohm resistance and the other an open circuit.
a: If it's not less than 1 ohm resistance replace the wire.

Hope this helps.

10-06-2009, 01:54 AM	#1 (permalink)
macasdude No Skills Join Date: Jan 2007 Posts: 49 Thanks: 8 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	grrrr 3 lights on dash? so while driving every time i hit a bump the 3 lights on my dash would come on Fan,Batt,ebrake light then when i hit another bump they would go off, when i turned blinkers on they would ocme on... well one day they stayed on while driving... after i parked the car all lights and stuff was out with car turned on, the next day my car wouldnt start! i jumped my car and it started but as soon as i turned on my headlights the car shut off.. Thinking it was my alternator i charged the batt, and checked my alternator one of the wires was loose so i tightend it and vola the lights were off.. i took the car to autozone and they said my alternator was good... 3 days later i hit a small bump and the same thing happes!! so i check the wire and its still tight?!!? thinking my batt is bad i take it to autozone and they say its bad so i get it replaced... the 3 lights are still on! so i have them check my alternator and they say its bad!?!? what can cause this? if i replace the alternator is it just goign to go bad again?? does the 3 lights meen a problem with alternator? need help thanx!! 1985 mr2 mk1 3sgte gen iii j-spec turbo engine swaped had car for about 6 months and never had this problem.. had my fueltank swaped and the problem started a day later O.o

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10-06-2009, 03:33 AM	#2 (permalink)
jimmer411 NA > Boost Join Date: Mar 2008 Location: Enumclaw, WA Posts: 112 Thanks: 1 Thanked 4 Times in 4 Posts My Google Map iTrader Rating: (0/0% )	3 lights is almost always alt.

10-06-2009, 04:06 AM	#3 (permalink)
PumpMag MR2 MKI Enthusiast Join Date: Apr 2009 Location: Southern California Posts: 52 Thanks: 0 Thanked 1 Time in 1 Post iTrader Rating: (0/0% )	The 3 lights on usually indicate the alternator going bad. If your battery is more than 2 years old, I recommend replacing it also.

10-06-2009, 04:11 AM	#4 (permalink)
PumpMag MR2 MKI Enthusiast Join Date: Apr 2009 Location: Southern California Posts: 52 Thanks: 0 Thanked 1 Time in 1 Post iTrader Rating: (0/0% )	If you just bought a new battery and have trouble starting, a bad alternator would not sufficiently recharge it. Use a voltmeter to check if the new battery is below 12 volts.

10-06-2009, 10:06 AM	#5 (permalink)
muffinman U-P-G-R-A-Y-E-D-D Join Date: Jan 2008 Location: Sunny South Florida Posts: 5,880 Thanks: 53 Thanked 283 Times in 272 Posts Blog Entries: 1 My Google Map iTrader Rating: (2/100% )	possibly a short in the alt which is why everytime you hit a bump it acted up but the 3 lights are always some sort of problem with the charging system.GL

10-07-2009, 10:44 AM	#6 (permalink)
macasdude No Skills Join Date: Jan 2007 Posts: 49 Thanks: 8 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	thanx getting the alt replaced today well see how it goes

10-11-2009, 10:05 PM	#7 (permalink)
tjmr2 Cage Fighter Join Date: Jan 2008 Location: Colorado Posts: 410 Thanks: 0 Thanked 62 Times in 59 Posts My Google Map iTrader Rating: (0/0% )	The three lights are all powered from different circuits (as in charge, cooling and brake) and can be activated in two ways. All three circuits use a diode in the circuit to control current flow (think of a diode as a valve that only allows current to flow in one direction). When you pull your emergency brake for instance it closes the switch that grounds the brake light to the chassis. Same for the other two lights, when each circuit needs to show a problem it completes the circuit by grounding the light (they have constant voltage applied to one side of the bulb and the other side is switched to ground), seems backwards. All three lights are tied together in only one place, and that is the L terminal on the alternator. (the 89 BGB shows it as the yellow wire) This wire connects the L terminal on the alternator to the 5A charge fuse (in the fuse box by the battery) then to the three lights. There must be more current & voltage applied through the charge fuse from terminal L on the alternator than is applied to the other side of the lights by the individual circuits to keep the lights from turning on. This is where the diode in each circuit comes into play. If all three lights are on they are using terminal L on the alternator as a ground. To test all this: 1: Remove 5A charge fuse & turn on ignition. a: Charge light should be off, brake and cooling should be on. b: Using a meter check both terminals in the fuse block to ground, one should have 12v. Make note of which terminal has voltage. 2: Start car. a: Charge light still off, brake and cooling off. b: Using a test meter check both terminals of the charge fuse to ground, both should now show 12v. If only the terminal from step 1 has voltage you have a problem either with the alternator or wiring between the alternator and fuse block. Can perform either steps 3 or 4 next. 3: Block up car and connect the meter between terminal L on the alternator and ground. a: Start engine. b: + 12v terminal L on alternator is good. c: 0v Replace alternator. 4: With engine off test the resistance between terminal L on the alternator and the charge fuse. One side of the charge fuse should have almost 0 ohm resistance and the other an open circuit. a: If it's not less than 1 ohm resistance replace the wire. Hope this helps.