Everything Dims!!!

[Xargon321]

At idle Everything slows down heater blower , Dash lights, head lights, i step on the gas it comes back. its a 74 260z it has new alt and vr belts tight, fuses are ok.

[beandip]

Sounds like the battery is some what discharged. How far do you generally drive the car when you start her up? I ask how far , because it takes a bit to replace the charge in the battery after start up. If after start up if the lights are turned on and or the heater fan , or any other electrical draw , it will take that much longer to replenish the charge in the batt. . If your regulater is adjustable it could require being set to a higher rate. If you have a charger , charge the batt and then when you start the engine after it is fully charged you should see the lights dim only slightly at idle . How old is the batt. it may be at the end of it's useful life, especially in this cold weather. One more thing check the posts connections on the battery if AT ALL corodded disassemble and clean . This alone could be the cause . Also, clean the top of the batt of any dirt and or oil . It is a good thing to rince the whole batt. and area with soda water solution to remove any acid from the sheet metal on the inner fender and frame rail below the batt. . If rust is noted in the area of the batt it is from the acid . best of luck Gary:classic:

[Xargon321]

ok thats the last thing really left thats hasent been really checked over, the posts have been cleaned as well as the cables at both ends but i havent checked the charge, it came out of my old car that the cam broke in when i was fixing this one up. i went threw my haymes book after and thought of the battery, i have a optima battery in my 65 stang that i can swap out as i dont drive the stang everyday. ill try that and see if it helps

also at idle when it dims can the ignition not be getting 12v? causeing a rich mixture?

thanks for the help!!

[Xargon321]

well its not the battery i swap that out this morning with my optima and it still does it, this also seems to point at my starter being stupid as it has been a pain to crank the engine over in the morning and when it has been sitting for a while, some time it cranks fine then i get a click noise then it slows down like a low battery mabey solenoid?

On the Everything dims topic it really only seems to do it when i turn the lights on.

[TomoHawk]

I agree that an older battery would lose power while sitting.

Did you get your alternator checked out? Voltage regulator too. You need to keep the battery full all the time to keep it working right. Never let a lead-acid battery sit while not at ful voltage.

[hls30.com]

What kind of aftermarket equipment is in the car? Sterio, Amp, DVD?

[Xargon321]

ok First the alt and vr are new i changed those when i got the car as they where bad, the battery is a gelcell optima battery that i just swap in today with no change, the only aftermarket thing in the car is a clarion stereo and two speakers, i dont even have them on when it does this, its really visable when the lights are on and not so much when they are off.

[hls30.com]

Check the wires coming off the alternator as well, if a PO didn't secure the battery, took a turn and dumped it into the engine it could have shorted against the hood and partially burnt your alternator wiring. If you don't find anything there, use a vom to measure the voltage difference between the engine and the car body, if the difference is not 0, make up a good ground wire to go from the engine to the body-you could have a weak ground.

[Xargon321]

well sorry i havent gotten back to you but found things that needed to be fixed right away(oil leak), Just how do i check the volt difference between engine and the body? the red should be on the engine and black on the body? any specific place to check it from?? i have a digital Multi meteri can use,

also id the alt spining enough at idle to charge the batterey with a load on it? my idles about 800, is this a common thing in z's? i thought of getting a smaller pully to run the alt faster would this hurt anything??

[hls30.com]

Most digital multimeters don't care about polarity, an in checking the voltage drop from the body to the engine it really won't matter. Put one probe on a machined surface of the block (usually there is a little of the deck the head bolts to sticking out)

and the other probe on the negative terminal of the battery. Anything other than 0(a negative reading is still not 0) or really close means you probably need to clean your connections on the negative battery lead, replace the wire, or add another ground strap the the block.

In my '73 the stock alternator will charge the battery at idle-the ammeter moves toward the "+" slightly at adle after starting. Putting a smaller pulley on the alternator will lower the charging ability of the alternator at every RPM. That means that you will have less-if any-charging at idle depending on the size of the new pulley. If you spend a lot of time waiting at stoplights, or cruizing below 1500 rpm, and have some high current items-major sterio, running lights, use the A/C, you could run your battery down-several of the electrical problems you have had-and repaired would be enough to convince me to leave the stock pulley alone, clean all of the contacts on at least the primary electrical system, and maybe upgrade the alternator.

Will

[ChrisA]

Hi Guys, from what I have been reading on various Googled sites, dimming lights at idle is not easy to correct. I read one site that said the alternator cannot supply enough power at idle with several loads on. My own car is exactly the same as Xargon's. It's rainy and cold here today so I had on the heater/wipers/headlites/stereo/electric fuel pump/rear defroster. Since my car has the original 40 amp alternator, I am putting a tremendous load on the alt at idle. The unit must spin at a certain rpm to excite the charging side enough to counteract the load. So naturally when you rev her up everything brightens/speeds up. I suppose you could add up the amp draw of everything that's running but what difference would it make. The alternator is not doing its job. BUT--another site said to clean every ground connection in the engine bay and add some 4 gauge ground wires between the engine and the body. Since we have cars that are 30 or more years old there is corrosion between wire connectors and their mating connection. When its bright and dry out with just my fuel pump drawing power it still slows down at idle. Every Z car I have ever owned (4) does this with the stock 40-45 amp allternator. Much luck all!!

[Xargon321]

well i checked the ground and it only read about .007-.008 volts

thats with the engine at idle with no accesorys running. should i have the head lights on when i do this?

also i though going to a smaller pully would increase the alts rpm at idle? causeing it to produce voltage at a lower engine rpm?