Lights Dim Then Bright Again

[yank30265]

im back again. my lights dim headlights instrument panel everything )when I hit the brake pedal or,raise the window lower the window. Whenever some kind of load is put on the sytem it happens, but just for a sec then come right back. i tried the wiring harness under the left hinge in the trunk as suggested, no broken white wire no broken any wire. Tried changing the box on left side of trunk these wires were plugged into; whats the name of that box it says lamp failure on it. I had the wrong box so my brake lights went out all together. Put the old box in. Tried new battery as suggested; same problems. Im not sure whats left; brake pedal switch? I changed one on my 94 ranger but that was when brake lights went out all together and the switch fixed it. Car has a new alternator in it i replaced because my battery kept going dead. Battery is fine now and the old alt tested good so that could've been bad connection at Alt. When checked w/ volt meter there is a quick drop then goes right back as quick as the lights come back; like a blink of an eye but very annoying. What else might this be?

2nd problem of many; car wont come out of park anymore w/o hitting override button; someone told me there is a sensor under the console by the shifter... anybody with any input on any of my problems let me know; You were great with the first suggestions but i need some more. Answer all; some parts; none; or tell me you have the same problem; any questions you might need me to answer to help you answer mine are fine. Thank you for all the suggestions

[curiousB]

im back again. my lights dim headlights instrument panel everything )when I hit the brake pedal or,raise the window lower the window. Whenever some kind of load is put on the sytem it happens, but just for a sec then come right back. i tried the wiring harness under the left hinge in the trunk as suggested, no broken white wire no broken any wire. Tried changing the box on left side of trunk these wires were plugged into; whats the name of that box it says lamp failure on it. I had the wrong box so my brake lights went out all together. Put the old box in. Tried new battery as suggested; same problems. Im not sure whats left; brake pedal switch? I changed one on my 94 ranger but that was when brake lights went out all together and the switch fixed it. Car has a new alternator in it i replaced because my battery kept going dead. Battery is fine now and the old alt tested good so that could've been bad connection at Alt. When checked w/ volt meter there is a quick drop then goes right back as quick as the lights come back; like a blink of an eye but very annoying. What else might this be?

Sounds like the alternator has some sort of lag. It should react to the load changes almost instantly so it sounds like the voltage regulator (in the alternator) is faulty. Is it a brand new alternator or a rebuilt? Of course loose or corroded wires from battery to alternator will create problems too so be sure those are clean and torqued down well.

[yank30265]

im back again. my lights dim headlights instrument panel everything )when I hit the brake pedal or,raise the window lower the window. Whenever some kind of load is put on the sytem it happens, but just for a sec then come right back. i tried the wiring harness under the left hinge in the trunk as suggested, no broken white wire no broken any wire. Tried changing the box on left side of trunk these wires were plugged into; whats the name of that box it says lamp failure on it. I had the wrong box so my brake lights went out all together. Put the old box in. Tried new battery as suggested; same problems. Im not sure whats left; brake pedal switch? I changed one on my 94 ranger but that was when brake lights went out all together and the switch fixed it. Car has a new alternator in it i replaced because my battery kept going dead. Battery is fine now and the old alt tested good so that could've been bad connection at Alt. When checked w/ volt meter there is a quick drop then goes right back as quick as the lights come back; like a blink of an eye but very annoying. What else might this be?

Sounds like the alternator has some sort of lag. It should react to the load changes almost instantly so it sounds like the voltage regulator (in the alternator) is faulty. Is it a brand new alternator or a rebuilt? Of course loose or corroded wires from battery to alternator will create problems too so be sure those are clean and torqued down well.

I think its got to be the wires going from the alt to ground or alt to starter; i hate to ask this question because i might not like the answer but here goes.... where is the starter on a 90 ls400 and is it easy to get to the positive cable at the starter?

[steve2006]

If you had a duff alternator your battery would be going flat.

Check the mega common problem of the trunk hinge wiring loom and repair as required before going anywhere else.

[jschmidt]

im back again. my lights dim headlights instrument panel everything )when I hit the brake pedal or,raise the window lower the window. Whenever some kind of load is put on the sytem it happens, but just for a sec then come right back. i tried the wiring harness under the left hinge in the trunk as suggested, no broken white wire no broken any wire. Tried changing the box on left side of trunk these wires were plugged into; whats the name of that box it says lamp failure on it. I had the wrong box so my brake lights went out all together. Put the old box in. Tried new battery as suggested; same problems. Im not sure whats left; brake pedal switch? I changed one on my 94 ranger but that was when brake lights went out all together and the switch fixed it. Car has a new alternator in it i replaced because my battery kept going dead. Battery is fine now and the old alt tested good so that could've been bad connection at Alt. When checked w/ volt meter there is a quick drop then goes right back as quick as the lights come back; like a blink of an eye but very annoying. What else might this be?

Sounds like the alternator has some sort of lag. It should react to the load changes almost instantly so it sounds like the voltage regulator (in the alternator) is faulty. Is it a brand new alternator or a rebuilt? Of course loose or corroded wires from battery to alternator will create problems too so be sure those are clean and torqued down well.

Had what sounds like the exact same problem. It went on for a long time. Had Lexus check it out and they said it was 'normal'. I new it wasm't. Had many mechanics check variuos things, but know one could find the problem. Battery was good ect. Then one day by accident, I was checking the battery agian and took off the battry clamp (I think it was the '+' side) and found that the clamp was accually cracked right though. You could hardly even see it. The clamp would tighten up to what you think was a good tight connection to the post, but it wasn't. A new $2.00 clamp at Wal-mart and 5 minutes, the problem was fixed. What a drag for such a liitle problem Hope this is the case for you.

As for the shifter problem. It could very well be the selinoid switch beside the shifter. I relpaced mine a few years back. You should here a faint 'click' if you put you ear near the shifter and press the brake with you hand. If you don't then the switch is likley the problem.

Hope this helps.

[dpellet]

I have a 91 and am having the same thing happen. This happens when I go into reverse as well. Quick load drop then back to normal, I notice my heater fan slowing down when this occurs as well. This was happening with the old alternator as well so I don't think it's the regulator.

Couple of commonalities, I just changed out my Alternator when I did my timing belt and water pump, old one had p/s fluid on it and although it was working I new it was only a matter of time.

I have repaired broken wires in the loom before, it's cold out here again so I am going to have a look at them again and also double check the tightness of ground and alternator leads. I to replaced my battery when it died at -40 last weekend.

Keep us posted.

Starter is a pita, located in the V of the block (under intake system).. If you have to go there, plan for a solid day to day and a half. Lots of things to clean and check while your in there and also a good time to do leaky valve cover gaskets/tune up etc..!

With your shifter, could there be some play going on there, not sure but perhaps there is an adjuster of some sort and your geting hung up on something? Not to sure on this one.

Cheers!

[curiousB]

I have a 91 and am having the same thing happen. This happens when I go into reverse as well. Quick load drop then back to normal, I notice my heater fan slowing down when this occurs as well. This was happening with the old alternator as well so I don't think it's the regulator.

Couple of commonalities, I just changed out my Alternator when I did my timing belt and water pump, old one had p/s fluid on it and although it was working I new it was only a matter of time.

I have repaired broken wires in the loom before, it's cold out here again so I am going to have a look at them again and also double check the tightness of ground and alternator leads. I to replaced my battery when it died at -40 last weekend.

Keep us posted.

Well in cold places, especially Alberta, everything gets magnified. The car is harder to start over (requires more cranking current), the battery has higher series resistance (less able to supply the needed cranking current). This is why they make battery blankets. Just warming the battery 20 or so degrees dramatically raises its cranking current when outside is -40 degrees. Loose battery, alternator connections that worked fine in warmer weather start to become probelms. I'd always advise clean the bulky wires (they're the one doing the heavy current) at the battery, alternator, and starter solenoid. Wire brush the corrosion off and torque down well with a wrench. If it wiggles then it's too loose. You shouldn't be able to move the connector with your bare hand.

A temporary fix at the battery post in the cold weather is to get a #10 sheet metal screw and drive it in at the gap between the post and the clamp (for old style lead post batteries). Sometimes its just too cold to fix it right and better to get going and do it properly on a warmer day.

[yank30265]

If you had a duff alternator your battery would be going flat.

Check the mega common problem of the trunk hinge wiring loom and repair as required before going anywhere else.

yea that was where I went first the harness under left trunk hinge; no broken wires there could it be the switch those wires are plugged into? its not only when i hit the brakes it happens whenever i put a load on the car; raise lower the windows etc; I also get the fan slow down when its on and when i hit the gas the fan speeds up again; new alt didnt fix the problem but im thinking corrosion on wires Not at battery im sure of and not on alt im sure of so its got to be wherever these wires go. is the starter solinoid on the starter like most cars or is it accessable? ive heard if i need to get to the starter its a lot of work

[curiousB]

If you had a duff alternator your battery would be going flat.

Check the mega common problem of the trunk hinge wiring loom and repair as required before going anywhere else.

yea that was where I went first the harness under left trunk hinge; no broken wires there could it be the switch those wires are plugged into? its not only when i hit the brakes it happens whenever i put a load on the car; raise lower the windows etc; I also get the fan slow down when its on and when i hit the gas the fan speeds up again; new alt didnt fix the problem but im thinking corrosion on wires Not at battery im sure of and not on alt im sure of so its got to be wherever these wires go. is the starter solinoid on the starter like most cars or is it accessable? ive heard if i need to get to the starter its a lot of work

Starter is a pain. Its buried under the intake manifold. In your case though I doubt that is the problem as you get dimming with even slight loads that have nothing to do with starting the car. If you problem was difficult or hard to engage starter motor then I would look to solenoid but that doesn't seem your symptoms.

[yank30265]

If you had a duff alternator your battery would be going flat.

Check the mega common problem of the trunk hinge wiring loom and repair as required before going anywhere else.

yea that was where I went first the harness under left trunk hinge; no broken wires there could it be the switch those wires are plugged into? its not only when i hit the brakes it happens whenever i put a load on the car; raise lower the windows etc; I also get the fan slow down when its on and when i hit the gas the fan speeds up again; new alt didnt fix the problem but im thinking corrosion on wires Not at battery im sure of and not on alt im sure of so its got to be wherever these wires go. is the starter solinoid on the starter like most cars or is it accessable? ive heard if i need to get to the starter its a lot of work

Starter is a pain. Its buried under the intake manifold. In your case though I doubt that is the problem as you get dimming with even slight loads that have nothing to do with starting the car. If you problem was difficult or hard to engage starter motor then I would look to solenoid but that doesn't seem your symptoms.

i noticed that when the car iss off and I open the door at night; then hit the lock button the dome light even dims; does this help pinpoint anything?

[curiousB]

It just seems that it is a loose or corroded connector to me. Maybe the ground strap at the battery or the other chassis ground point end. If you have a voltmeter it would be good to measure battery voltage at the battery + and - posts. Then turn something on and see if that voltage drops much. If the load doesn't drop the voltage then the voltage is dropping over some poor connection between the battery and the load. You could try measuring the voltage from the - battery terminal to a good ground on the block and then see if it bounces around when you switch on loads. If the voltage goes more than 0.2 volts that indicates a poor link between - post and chassis. You can do the same on the + side. Measure from + battery post to the + side of a load. Turn on and off that load and see if voltage moves around. Again anything much more than 0.2 volts would indicate some pretty good voltage drops to battery and the likely culprit.

[POLO2349]

I've been having the same thing happen in Georgia. It started pretty subtle Saturday night then Sunday it got really bad on the highway, to the point when I hit the brakes my car almost shut down. I asked a friend of mine, who is a mechanic, and he said it sounded like the alternator. I went and had my battery and alternator tested; battery tested good and alternator tested bad. I'm replacing the alternator right now, so we'll see how that works.

[yank30265]

I've been having the same thing happen in Georgia. It started pretty subtle Saturday night then Sunday it got really bad on the highway, to the point when I hit the brakes my car almost shut down. I asked a friend of mine, who is a mechanic, and he said it sounded like the alternator. I went and had my battery and alternator tested; battery tested good and alternator tested bad. I'm replacing the alternator right now, so we'll see how that works.

let me know cuz I had the same problem and changed the alt and it got alittle better to the point where im at now but i had the old alt tested and it tested good some im thinking when i changed the alt something might have been going on at the alt connections. so now im wonderiung where the other ends are and what they look like

[yank30265]

im back again. my lights dim headlights instrument panel everything )when I hit the brake pedal or,raise the window lower the window. Whenever some kind of load is put on the sytem it happens, but just for a sec then come right back. i tried the wiring harness under the left hinge in the trunk as suggested, no broken white wire no broken any wire. Tried changing the box on left side of trunk these wires were plugged into; whats the name of that box it says lamp failure on it. I had the wrong box so my brake lights went out all together. Put the old box in. Tried new battery as suggested; same problems. Im not sure whats left; brake pedal switch? I changed one on my 94 ranger but that was when brake lights went out all together and the switch fixed it. Car has a new alternator in it i replaced because my battery kept going dead. Battery is fine now and the old alt tested good so that could've been bad connection at Alt. When checked w/ volt meter there is a quick drop then goes right back as quick as the lights come back; like a blink of an eye but very annoying. What else might this be?

Sounds like the alternator has some sort of lag. It should react to the load changes almost instantly so it sounds like the voltage regulator (in the alternator) is faulty. Is it a brand new alternator or a rebuilt? Of course loose or corroded wires from battery to alternator will create problems too so be sure those are clean and torqued down well.

Had what sounds like the exact same problem. It went on for a long time. Had Lexus check it out and they said it was 'normal'. I new it wasm't. Had many mechanics check variuos things, but know one could find the problem. Battery was good ect. Then one day by accident, I was checking the battery agian and took off the battry clamp (I think it was the '+' side) and found that the clamp was accually cracked right though. You could hardly even see it. The clamp would tighten up to what you think was a good tight connection to the post, but it wasn't. A new $2.00 clamp at Wal-mart and 5 minutes, the problem was fixed. What a drag for such a liitle problem Hope this is the case for you.

As for the shifter problem. It could very well be the selinoid switch beside the shifter. I relpaced mine a few years back. You should here a faint 'click' if you put you ear near the shifter and press the brake with you hand. If you don't then the switch is likley the problem.

Hope this helps.

doi you know what this switch might be called? i didnt hear a click when i pressed the pedal w/ my hand

[dpellet]

I had a chance to look at mine, negative connection looked tight but it was not. I need to change that at some point but I took the advice of an earlier post and put a sheet metal screw in the space between the bat. post and clamp and this has solved the problem. Reverse has no dimming and all other symptoms seem to be rectified.

Hope this helps!

[billydpowell]

One of my first gen's did the dim-bright thing,

I removed the battery cables from the battery, cleaned them and the battery post up,

put them back on and no more problem....

I learned the hard way a battery post will oxidize, but look clean, and still give you problems.

good luck on yours (get a second generation).

cheers