New alternator?

[marcmsj]

I'm trying to figure out if I have a dieing alternator or not. my dsm is a 92, with almost 130k miles on it. any time i turn my headlights on while my car is at idle, the rpms drop a good amount then go back up to normal. i also noticed that at idle, the dash lights aren't as bright as if it's revved up at like 3k rpm for example. and since i all trim pieces in the rear along with the backseat, i can hear the fuel pump and if i have the blinker on, i can hear the whining changing frequencies... i guess it's not getting enough power. anyway, my question is should i get a new alternator or could something else be causing this problem? bad ground maybe?

 

[Quasimondo]

Quick and easy way to check if alternator is going is by starting the car. With the engine running, disconnect the negative terminal of the battery. Your car should be running on alternator power alone. If it stumbles or dies, then your alternator is going. You can also put a multimeter to your battery and check the voltage with the engine running. Normal operating voltage is between 13.5 and 14 volts. If it's less than that, you might want to start shopping for a new alternator.

 

[marcmsj]

sounds good.. thanks.

 

[mitsutuner]

If you follow the procedure previously outilind, you could easily damage your ECU. Better way to check the alt is with a voltmeter.
check to voltage of the battery before & after you start the car--should go up after starting if the alt is working.

 

[2.4 turbo Hyped]

If you have a blitz turbo timer it shows battery voltage and you can monitor your alternator output by "eyeballing" this feature.

 

[marcmsj]

so i checked everything out yesterday with a voltmeter and everything came back normal. battery voltage with car turned off was 12.2

reading with car on was 14.2 and under load was 14.1

any other ideas why i'm getting this dimming effect?

 

[mitsutuner]

voltages sound good, measuring current in amps is slightly more conclusive.

motor idle too low
loose alt belt
battery, alt connections or possibly a fuse dirty,(look close at batt ground, clean & sand all connectors to shiny metal)
alt about to die from worn brushes,(time will tell, keep a charged battery jump box in the trunk, a must have for any mitsu product. If the alt & then batt goes dead, you can at least drive the car a short distance with the jump box attached--of course the hood won't close)
high wattage aftermarket stereo,(I have seen guys on some cars install a 2nd alt.!)

 

[marcmsj]

voltages sound good, measuring current in amps is slightly more conclusive.

motor idle too low
loose alt belt
battery, alt connections or possibly a fuse dirty,(look close at batt ground, clean & sand all connectors to shiny metal)
alt about to die from worn brushes,(time will tell, keep a charged battery jump box in the trunk, a must have for any mitsu product. If the alt & then batt goes dead, you can at least drive the car a short distance with the jump box attached--of course the hood won't close)
high wattage aftermarket stereo,(I have seen guys on some cars install a 2nd alt.!)

idle isn't too low.. it idles anywhere between 750 and 1000. belts are on nice and tight. will check ground connections and clean them off. stereo is just a simple alpine headunit powering just the front speakers (i removed the rear ones)

i know i should probably just go ahead and get a new alternator anyway since i have the original one on there... but that's money that won't go into other mods so i won't get one unless i really have to.

 

[mitsutuner]

I know that money song all too well.
my original alt lasted 137k.
You wouldn't have to replace the alt, you could:
have it rebuilt at an auto electric shop for less than $100
rebuilt it yourself, ez to do, kits are about $10-15-,
most likely all you need are the brushes, can be bought seperately, $5.
most recently I took the alt from a galant at pic&pull $35.

 

[marcmsj]

I know that money song all too well.
my original alt lasted 137k.
You wouldn't have to replace the alt, you could:
have it rebuilt at an auto electric shop for less than $100
rebuilt it yourself, ez to do, kits are about $10-15-,
most likely all you need are the brushes, can be bought seperately, $5.
most recently I took the alt from a galant at pic&pull $35.

i'll look into that, thanks..

i also think i should clean it out a bit, i don't wanna spay any engine cleaner or degreaser on it, but at the same time it's covered in gunk. any cleaning tips?

 

[mitsutuner]

I use throw-away rags slightly wettened with soapy water or regular cheap car wax---& cheap rubber gloves.
Engine degreaser fumes cause brain damage, spacey for days.

 

[2.4 turbo Hyped]

i'll look into that, thanks..

i also think i should clean it out a bit, i don't wanna spay any engine cleaner or degreaser on it, but at the same time it's covered in gunk. any cleaning tips?

I have soaked my engine bay numerous times on a cold engine with that coastal power clean purple stuff they sell at auto zone. You are not going to hurt anything underhood. I let it sit for about 10 minutes and then hose the whole engine bay down.

Check out my gallery for the super clean engine bay pics I am talking about.

 

[marcmsj]

I have soaked my engine bay numerous times on a cold engine with that coastal power clean purple stuff they sell at auto zone. You are not going to hurt anything underhood. I let it sit for about 10 minutes and then hose the whole engine bay down.

Check out my gallery for the super clean engine bay pics I am talking about.

looks good. i'm just especially concerned with the spark plug wells.. i know that if i get water in there, it's gonna be a PITA to get out/let air dry.

 

[2.4 turbo Hyped]

looks good. i'm just especially concerned with the spark plug wells.. i know that if i get water in there, it's gonna be a PITA to get out/let air dry.

Thats easy, start up the engine and drive somewhere, the heat from the head evaporates the water.

 

[mitsutuner]

If the motor is so grody that I don't want to touch anything, I take it to the coin op car wash & spray it soap & rinse with the motor running, & then drive until dry.
Many ways to clean the motor & not cause any damage under the hood, but I would limit the use of cleaning solvents that cause brain damage, equivalent to sniffing glue.
in CA we passed a propostion that requires all products that contain chemicals that are known to cause cancer have a warning label posted. You will see this warning on every single gas pump. Lock the gas nozzle & walk away from the car until it turns off. In big cities, the gas stations are required to have a seperate vapor return hose on the gas nozzle--it's hooked up to a big fan that sucks the vapors back inside their tank.

 

[marcmsj]

rinse with the motor running? i wouldn't want water touching my hot exhaust manifold...

 

[mitsutuner]

No reason to be paranoid, can't hurt the exhaust manifold, done it many times--do you drive your car in the rain? Did you ever hear of an exhaust manifold cracking after a rad hose rupture? & what about all that oil that drools down from your sometimes leaky VC gasket?
At the coin-op car wash, you can avoid any part that you are paranoid about, I avoid spraying the alt as water will get inside it & also the accessory drive belts--they'll just get squeaky after drying. Avoid the distributer cap too if you are still driving an older car that has one.
It is however, illegal to wash your engine bay at the car wash in California, pollution issues, everybody does it anyway. It's not much different than all the fluids leaking from all the cars on the road all the time, & the most serious issue is all the brake pad dust on the roads.

 

[marcmsj]

guess i am paranoid, but eh.. keeps me out of trouble

 

[2.4 turbo Hyped]

No reason to be paranoid, can't hurt the exhaust manifold, done it many times--do you drive your car in the rain? Did you ever hear of an exhaust manifold cracking after a rad hose rupture? & what about all that oil that drools down from your sometimes leaky VC gasket?
At the coin-op car wash, you can avoid any part that you are paranoid about, I avoid spraying the alt as water will get inside it & also the accessory drive belts--they'll just get squeaky after drying. Avoid the distributer cap too if you are still driving an older car that has one.
It is however, illegal to wash your engine bay at the car wash in California, pollution issues, everybody does it anyway. It's not much different than all the fluids leaking from all the cars on the road all the time, & the most serious issue is all the brake pad dust on the roads.

Let me write a little equation for you hot engine + water rinse=possible warped head/or a cracked block if the water is cold enough. Its never a good idea to spray water on a warmed up engine. Wait till its cold and then spray it.

 

[mitsutuner]

I will not let you write a little equation for me.
If what you are saying is true, you could never start a cold engine, or operate a motor in a cold climate. I have been cleaning motors at the car wash for over 30 years incident free. (duh,-water turns to ice at 32 degrees & will not flow from the car wash nozzle, but you can start & run your motor in sub-zero weather).
The only thing you don't to do is add cold water to an overtemped motor that has lost all of it's coolant from inside the motor--can crack a cast-iron block.

 

[marcmsj]

starting a cold engine and showering a warmed up engine are two different things but hey, that's just me. if it's been working for ya then great, i just don't think i would want to attempt anything like that. i would definately prefer to rinse it off with a cold engine.

 

[mitsutuner]

For sure, it's no fun to work on a dirty engine.
The alt. area in the engine bay of these DSMs needs to be looked at every time you pop the hood. I have heard of coolant, oil & exhaust dust causing problems & also the alt B+ wire arcing to the oil filter case. In my case I was being lazy & left the lower exhaust manifold heat shield off for about 3 months. The exhaust dust coated everything & the alt bearing next to the exhaust got really hard to turn, causing the alt belt to jump off the pulley.

 

[2.4 turbo Hyped]

starting a cold engine and showering a warmed up engine are two different things but hey, that's just me. if it's been working for ya then great, i just don't think i would want to attempt anything like that. i would definately prefer to rinse it off with a cold engine.

Some people learn the hard way.

 

[mitsutuner]

And how could I forget the PS fluid that drools down into the alt. when the PS hose fitting at the top of the PS pump leaks.
And the oil vapor that leaks out the top of the dipstick when the O-ring on the dipstick is worn & doesn't fit tight anymore.

 

[marcmsj]

And how could I forget the PS fluid that drools down into the alt. when the PS hose fitting at the top of the PS pump leaks.
And the oil vapor that leaks out the top of the dipstick when the O-ring on the dipstick is worn & doesn't fit tight anymore.

you seriously can't compare any of that to cold, or even ambient temperature water. as i'm sure you know, all fluids in your engine are far from ambient temperature and temp difference is what causes the problems.