all lights dimming, NEED HELP

[jasonporsche]

hi everyone. Got a problem. Last night when i was driving, it seemed like all my lights (headlights, dash lights, etc) were fluctuating brightness with the rpm of the engine. also sitting at a stop light or even driving at lower speeds the lights were getting noticibly brighter and dimmer. Even the dash lights were doing it along with the headlights. almost like an alternator. Now the voltage regulator was replaced a few thousand miles ago. I did noticed the belt was making a little noise and was kind of loose. Will this cause this problem. I don't think the alternator is bad because the battery stays charged. I mean the belt is pretty tigth but is howling and i can see a lot of movement. Mayeb that's all it is. I'm going on a liong trip and just wanted to be sure. anyone ever experienced this. Also , maybe thsi is normal, but the defroster fan speeed seems to work with the revs of the car too!lol. Hopefully all i have is a loose belt, but any advice is appreciated.

[jasonporsche]

also too. early this morning the alternator light blinked just a few moment but went off after i gave it some gas and it was just very faint. it has never come on and stay on!

[bell]

if the blet is slipping it could keep the alternator from charging properly, which could cause the dimming.
check the tension on the belt, remember that you need to keep all 6 shims inder the washer on the pulley.
i'd also check your battery connections for corrosion as that can cause similar problems, even if they look clean they could have corrosion so maybe clean them up anyway.

[kqw]

Hopefully it's the belt...Otherwise I think your alternator is getting ready to take a ......

[WERK I]

This may be slightly off topic, but has anyone experienced a change in the gauge readings when the headlight switch is turned on? I notice a change of -.5 bar oil pressure, a dip in the fuel gauge reading, and oil temp. I replaced the alternator about 5K miles ago(rebuilt Vertex unit). I can't really say when it started since I don't do that much night driving with the car.

[kqw]

The Original equipment for the '85 was a Paris-Rhone alternator and are you saying that Vertex rebuilt a Paris Rhone or did Vertex supply an alternative aftermarket voltage regulator?

[WERK I]

kqw,
The unit I got from Vertex was an original equipment unit that was rebuilt. It was a complete unit, which included a regulator/brush assembly.

[nhromyak]

It sounds like your regulator is "pulsing".

I presume this "pulsing" is happening at idle too, correct?

Or is this happening as you change RPMs?

Check voltage at idle and above 2500 rpms it should not go above 14.8 volts.

[jasonporsche]

ok, jsut got done tightening belt. took two shims out. Seems to have improved a little bit. when car is above 2 thousand rpm, the lights and stuff seem to stay pretty level. Now , i have noticed this condition on a few other 011s i have had. when at an idle and all accesories running, but just not this bad. Hopefully this will get me by on the trip. I checked the records and the regualtor was reaplaced about 4000 miles ago. Hopefuilly this will work, but lets check the voltage, i will post in a little while
thanks for all the help!

[WERK I]

Hi Nick,
It occurs indepently of engine speed. At idle or at higher engine speeds(i.e. 3500RPM). That is a good idea to check voltage at various speeds. I know it is not the ground strap from the trannie to chassis since I cleaned the area when I pulled the engine for the rebuild last spring, if that helps. It may have had this problem all along with the new rebuilt unit. I suppose it could be a flakey regulatorthat was never checked out properly when it was rebuilt.

[pwd72s]

http://www.systemsc.com/

You may find help in the diagnostics and trouble shooting sections of the above site...

[anh911]

Originally posted by WERK-I
Hi Nick,
It occurs indepently of engine speed. At idle or at higher engine speeds(i.e. 3500RPM). That is a good idea to check voltage at various speeds. I know it is not the ground strap from the trannie to chassis since I cleaned the area when I pulled the engine for the rebuild last spring, if that helps. It may have had this problem all along with the new rebuilt unit. I suppose it could be a flakey regulatorthat was never checked out properly when it was rebuilt.

You might also want to check the grounds for the instruments. It's been a while but I think most or all of them ground at one junction.

[nhromyak]

Originally posted by WERK-I
Hi Nick,
. I suppose it could be a flakey regulatorthat was never checked out properly when it was rebuilt.

That was my problem... the regulator checked out on the bench, but under load, it flaked (it made voltage spikes = "pulsed").

[jasonporsche]

ok, checked the voltage at idle and at 2500 rpm. voltqagae never got above 14.8. all you 911 guys though, don't your lights flicker a slight amount at idle when a lot of accesoories are running?

[nhromyak]

Originally posted by WERK-I
This may be slightly off topic, but has anyone experienced a change in the gauge readings when the headlight switch is turned on? I notice a change of -.5 bar oil pressure, a dip in the fuel gauge reading, and oil temp. I replaced the alternator about 5K miles ago(rebuilt Vertex unit). I can't really say when it started since I don't do that much night driving with the car.

Yep. My '73 did this, my dad's 80 does this, and my '85 does this.

[nhromyak]

Originally posted by jasonporsche

all you 911 guys though, don't your lights flicker a slight amount at idle when a lot of accesoories are running?

No.


The flickering could be voltage changes or amperage changes. It sounds like you need to go to an Autozone or Kragen and have them check your amperage output on your alternator.

It could be bad brushes on the alternator or a bad connection on the battery or a bad ground.

Good luck.

[jasonporsche]

can you replaced the brushes in the alternator. how bad of a job is it to take it out? also, anyone know any good places to get a reseonably priced one?

[jasonporsche]

how many amps should it be putting out?

[nhromyak]

I beleive they should be putting out 80 - 90 amps. I think the brushes are around $40. I am not sure what it takes to put them in though. I always have problems with motors and altenators with their little springs to hold the brushes in and such.

I have always found a rebuilt alternator, stator and brushes done for ~$100.00

But, get it checked to be sure.

[kqw]

Issues still pointing towards the Alternator.

Check back with Vertex, you may have a 12 month warranty.

By the way, I have NO pulsating at low idle in my Carrera. However, 3 years ago when I replaced my Alternator, the first one was faulty. The second one was/is fine.