75 chevy monza

[sportster96blk]

i have a power drain at a idle volts go from 14.4 down to around 11.5 only with the headlights on. there are two thick red wire coming off the alt. and they go to a four way connection with one thick red wire going to starter and a fourth one that is short that ends at a plug ?the other one goes in to the fuse box where should that plug go to? the battery maybe

[monzaaddict]

if your referring to the plug on the firewall near the power brake booster it is for the auxillary pusher fan that is included on a/c cars.

[sportster96blk]

ok well ive still got a power drain at an idle only seems to happen when headlights are on

[gerbsinmd]

Do you have a power drain, or an alternator that can't keep up?

[cjbiagi]

Alternators do not put out maximum current at idle but you should not be seeing a discharge condition unless you have some other accessories running too. The biggest problem with older cars are the wiring connections. When you are dealing with low voltage (such as a car with 12 volts) it does not take a lot of resistance to start developing a voltage drop. Since you are dealing with 35 year old wires have you checked the battery connections at the starter, as well as your grounds? While it may seem a bit overwhelming you may want to start looking closely at as many connections as you can and start disassembling and cleaning them. There is also a de-ox chemcal that will help clean up those connections. Start with the battery and starter as well as the engine block ground and small chassis ground wire on the drivers side fender. It could very well be just a tired alternator but cleaning your connections will go a long way to help. Clean the terminals at the headlamps too as any higher resistance there will create more current drain. Also clean all of your alternator connections. The other thing you may want to test is the voltage right at the battery, does that drop to 11 volts too or is that still ok? If the voltage at the battery is good (above 14 volts or so) then you definetly have some voltage drop issues in the wiring connections. Here's a decent site to get some info

http://www.aa1car.com/library/tselec.htm

[sportster96blk]

that is a very helpful site thank you .all components in car are new and so are the connections the only possible problem is the wiring that is 35years old .i shortened some of the engine wires because they were to long, separated them and put plastic shrouding around them to help isolate them better. now i need to check all connections at headlight and factory installed soldar connections. boy what a headache it seem like what can go wrong will go wrong no matter what with this car . but the end result is near drag races start in march i think my car will win a trophy i hope with my foot on the gas pedal not brake .lol. we,ll see

[sportster96blk]

i seem to have two issues, a alt. that's rated at100amps only putting out 73 amps and my car with all electrical stuff on is drawing 60amps so I'm going to have alt. respooled at 120apms and see if it solves me problem. all elect.items include head and tail light, windsheild wipers, two ten inch pusher fans, heater fan= 60amps + am,fm radio 50wts times 4 and a 400wt power amp......and anouther 400wt power amp will be added later for sub wolfers

[spencerforhire]

A quick fix for poor charging at idle is to install a smaller pulley on the alternator; going from a 3" down to a 2" pulley will increase the speed by 1/3rd. I've had to do this on a couple of customers' cars that had underdrive crank pulleys( I don't like these) previously installed. Slowing down all the driven accessories may free up a couple of horsepower, but if the car won't charge at idle, they're useless on the street.
P.S.- My apologies for not replying to your P.M.

[cjbiagi]

A alternator will only put out what is needed based upon the given load. It does put out more than required. If you put a 60 amp load on a 100 amp alternator it will only put out 60 amps. If you put a 10 amp load on a 100 amp alternator it will only put out 10 amps. You could have a bad voltage regulator inside the alternator but without any voltage measurements at the battery and headlights it's hard to know what's going on.

[sportster96blk]

sometimes it charges and sometimes it dont, i took the car to acme auto electrical and they were unable to do anything about my problem it has the smallest pulley available it puts out a good charge at anything above idle under full electrical load and even put out a good charge without a full load at idle the only thing not on was the wiper and the charge stay good turn on the wiper and it drops but i could leave other things off with the same results meaning all on but heater all still good

[cjbiagi]

The voltage should not drop that much at idle, certainly something is wrong. Is this a standard 3 wire alternator?

[72 SS PNL]

what about the crank pulley ? is it a smaller pulley or larger pulley ? a larger crank pulley should speed up the alt as well as other items attached to it

also maybe try bringing your idle speed up a little to help out

[cjbiagi]

A 100 amp alternator should be able to put out probably at least 50 amps at idle. I don't think any alternator puts out max amps at idle but it doesn't sound like you are drawing that much current. You need to measure the voltage at the back of the alternator, the battery, as well as the headlights when this occurs. Maybe the voltage regulator is bad. The only time I see my voltage drop a little is when the car (and wiring) gets hot. Then I will notice my voltage drops a bit to maybe the high 13 volt range vs my normal high 14 volts. Heat increases resistance in the components and wiring which will create a voltage drop but it is still plenty high, well above battery voltage. As mentioned make sure your pulleys are the correct diameter, it's probably not worth playing around with changing pulley diameters from stock.

[sportster96blk]

well the pulley thing has got me bothered i was told the smaller pulley was the one i wanted i need to buy my own meter so i can get my own measurements my gauges say there's a real problem and seems to be heat induced a friend has recommended a shop to go to that might be better then the last shop. my biggest problem is no ebrake and my issues only occurs in drive at a idle.well I'm going to check out this new shop and see what they say. ill most likely be buying my own meter and doing it my self ill post more tomorrow and ill look in to pulley speeds

[72 SS PNL]

smaller alt pulley YES

larger crank pulley YES , smaller crank pulley NO

now for racing you can mess with the pulley ratios , and use smaller crank pullies to lessen the HP draw from the accessories driven off the crank , running larger water pump and alt pulleys , but they are mostly drag use or extended HIGH rpm use

if your idle is at 6-700 now try bumping it up to 9-1000 and see if that changes the idle voltage