Voltage drop help.

[ponchopwr70]

Well I need some help. Last year my cars battery would die when I sat in the pits idleing. Testing showed I was only putting out 11.98 volts at idle with my lights, lincoln mark viii fan, radio and blower motor. I also noticed I was getting a .8 voltage drop between the battery and alternator. So I decided to rewire the engine harness. I ran a new charging wire and I'm still having the same problem except I only have a .01 voltage drop and 12.02 volts at idle. The fan is wired through a relay and the alternator was just tested and put out 108 amps at 2000rpms(on a bench) with a load at a local alt shop. Its an si (I belive 10si) with 3 wire hook up. If I bring my engine rpms up to 1100 the volts go up to 14.5, I've experimented with pulley sizes and I'm using the smallest I can with out throwing belts. Its a powermaster 2.375 dia deep groove and my crank pulley is 7" march pulley. What do I do?

[parsonsj]

I suffered similar problems until I went to 3:1 on the pulley ratio between crank and alternator. You are actually just there too. If it isn't too expensive, I'd try a 7.5" or 8" crank pulley. I think that will fix you up.

jp

[MonzaRacer]

OK regardless of the pulley setup your simply going to over heat and burn up your alternator.
I have seen so many of those powermaster alts not charge at idle.
I use plain old AC Delco reman CSI alternators with much better results as they have digital regulators I find they control amperage much better.
Also they have much better delta windings (the charging stator).
Now was your voltage drop while running or key off?
AS for me I would add an 8 ga wire from the alternator to the battery (fuse link is up to you) and make sure your key on wiring is getting full voltage (within .5 volts) of battery or atleast within .1 volt at the power wire before the key switch(ie power into your key switch) this would mean you have no voltage drop through the switch.
Electrical isnt as hard as most think but if you think an alternator at low speed can put out 20 -30 amps and keep doing it AND be compact then you dont understand how an alternator works, and as it has to make amps at low speed it gets hot which raises the resistance through the brushes and that decreases the efficiency of the unit.
Even if it says its a 200 amp model I rarely see them making anywhere near that even when stressed by my 600 amp carbon pile tester.
But I have used several CSI-144 based alternators, while larger body they do make within 90-95 percent of rated amperage.
I have also had several battery brands that dont take charge well when system is loaded,Deka is one of them.
Right now I am using a Blem Optima and its been a wonderfull battery,heck it ran for 5 days with no alternator output at all (charge wire broke) and I drove 4 of them in the dark with lights and high blower and such.
Also after checking it at idle you should have gave it 500 rpms and see where the voltage goes.
A lot of alternators as they wear the brushes then the alt wont put out anything till they have a few extra rpms then the regualtor will excite.
Also if its a "self excite" alt it wont work at idle well if at all.
Good Luck.
Lee Abel
AFTERMARKET PERFORMANCE

[ponchopwr70]

I think I just need a cs 130. My charging wire is a 8 ga wire, volt meter reads the same as the battery with key on. When I jump the rpms up 300 the voltage is around 14.5 (this is with a load on it) With no load the alternator puts out 13.5 at idle.

[TheMonkey]

Frank-

one of the advantages of a 3 wire alternator is that the #1 connector (red wire out of CS pigtail) is wired to the main power lug to read voltage. some installations incorrectly just jump that wire to the charge lug on the back of the alternator. this will work, but you will be reading voltage after the voltage drop from the main lug to the alt (which can be big if the charge wire is undersized). make sure your #1 terminal red wire is reading voltage from the same spot that your main positive battery lug is located, and not simply jumpered.

also, measure voltage at your battery and compare that to a voltage after the fuse block. sometimes with original fuse blocks, or under-rated blocks, there is just too much power trying to jam through it creating a voltage drop. if the voltage drop is bigger when you turn on your lights, consider wiring in some relays for those and get power directly from the battery (don't forget to fuse going into the relays). as a bonus your lights will be brighter too.

Scott.

[6'9"Witha69]

This link should be a sticky at the top of this section! Read here and call Mark for all you will ever need to know.

www.madelectrical.com/electrical-tech.shtml

^^Lee knows his stuff too.

[ponchopwr70]

No link?

[MonzaRacer]

too bad no one listens. I have been using CSI133 alts and CSI 144 for years. The key on wire only needs powerto "activate" the regulator. I ususally loop another terminal(Ill have to dig up my alt plug from mine ) to the battery lug. I ran this alt from 94 till 06 on 2 different cars.That alternator has probably 200,000 miles on it before the brushes wore out.
I used the old AC Delco number alt 321-411.