Headlights dim after braking - Toyota Nation Forum : Toyota Car and Truck Forums

danpluso · 12-24-2009, 01:40 AM

Hello guys and gals!

I have a 1997 Toyota Corolla that I just bought recently off my brother in-law. Since I bought it, I have replaced the steering pump, the front brake pads and rotors, and the motor mounts. My Corolla seems to have a problem with dimming headlights when I brake and come to a complete stop. I can also noticeably hear the interior fan/fans (not sure if there is more then one or not) declining in speed once I come to a complete stop.

The headlights will dim a little bit when I just tap on the brakes going at city speed but when I come to a stop sign and make a complete stop, the headlights dimming and fan speed decreasing are very noticeable.

I have an aftermarket amp and sub installed but they are currently not powered up because I don't even have a cd deck installed yet to send the remote turn on signal. I did have the Positive battery connector replaced because I couldn't get my amp connected to the original connector due to lots of rust and the nut just not budging. Only problem is... I never did night driving in my car before I got that connector replaced so I am not sure if the replacement of the connector is what is causing it or not. It is definately a massive connector compared to the negative connector. Not sure if that would make any difference or not..

Any ideas? I would hate to see what happens once I have my cd deck, amp and sub running. Could I just need a new battery? Or maybe replacing the battery cables would help?

iToaster · 12-24-2009, 03:47 AM

Get the alternator tested and clean your battery terminals.

Bitter · 12-24-2009, 09:41 AM

mine does that as well, its kind of normal. automatic right? if you go into neutral and rev it just a hair it brightens back up yea?

replace the stock ground cables with some heavier gauge ones and run thicker cable from the alt to battery as well. the stock cables a touch on the thin side when you have EVERYTHING running. i added a an extra ground from the battery to engine at the intake manifold and noticed a little smoother idle and less idle speed dip when i turned things on or when the cooling fans came on. i'm sure upgrading the body ground or running an extra one would help even more.

danpluso · 12-24-2009, 02:39 PM

Yes it is an automatic and yes when I put it in neutral a rev up the engine it does brighten up a bit however I haven't tried doing that when I come to a complete stop and the lights are their dimmest. When I brake and come to a complete stop it really dims down to the point that my high beams look like the normal headlights and the fan speed drops to at least half the speed.

I will get my alternator tested and then look into the battery terminals and cables. Thanks for the advice guys.

Bitter · 12-24-2009, 08:51 PM

mines not that bad. whats your in gear idle speed? mines around 600-650.

danpluso · 12-25-2009, 02:48 AM

I have no idea.. I'm not very mechanical smart.. My area of expertise is in computers..

My mechanic seemed to think the idle was good... That's all I know.. I may take it to him to get the alternator tested but if it is simply in need of a new ground cable or something, I would hate to pay him to change it as I could probably figure it out myself. Is there any way to test an alternator myself with a simple analog multimeter?? I'll do some googling.

Bitter · 12-25-2009, 09:44 AM

kind of....

you want to measure voltage at the alt, at the battery, and at an accessory. all should be very close to each other. but you need to do so when the system is loaded down and acting up, voltage should stay well above the battery at 12.6. should hang around 13-14.7. the alt only generates whats needed by the system and its really amps you want to look at anyways. what you need to do is an amperage test of the alt. typically how they test them off the car is at around 2000 rpm, but an alt can be bad in a way that it passes that but would fail at idle speeds. goto an autoparts place that can test it on the car. with all accessories off at idle in park have them load test it OR just put it in gear and turn all the stuff on that makes the lights dim and see what amperage its able to put out. it could be going low on amps.

but the grounds are pretty easy to do, you can buy heavy gauge cables cut with ends just for cars at most autoparts stores. they're sold as battery cable kits. i would re-run the chassis ground and engine ground with new cable and clean where they connect very well to bare shiny metal.

danpluso · 12-26-2009, 06:41 PM

Okay thanks! I guess I will bring it to the shop to get them to test the alternator and then go from there.