Hey guys, I'm running a 94 amp alternator on my car and at night if I come to a stop with my headlights on, dual electric cooling fans going, possibly heater blower on, brake lights on (obviously, stopped ), radio on, and possibly a turn signal going, when the car drops to idle (500-600 rpm) my voltmemter drops down fairly drastically (well below 13 volts) and I can see my dash lights dim, etc. As long as the engine is turning 1000 rpm or more the voltmeter stays above 13 volts. This seems *fairly* normal to me, I just wanted to check and see if other people have the same type of thing happening. I think I want to put a 140 amp alternator on eventually, but I figured I'd check in and see if maybe this is a bigger problem than I think it is and I should check into my electrical system further. What experiences do you all have with this?

-Paul

 

Sounds exactly like what my car is doing. I had a powermaster 140 amp alternator in that died after only 4 months while my voltage readings were like what you're describing. Now I just put a new Delco 105 amp alternator in, and it lasted a day. FRIED. If you figure out what the deal is with your voltage, you let me know ok???

 

Interesting to hear that. I haven't had trouble with the alternator, the 94 amp has been on there for a while, and it does fine voltage-wise during the day, even with the cooling fans going. It's been keeping the battery charged just fine too, even with night driving in town. I don't think my problem is as major as yours, but I'll keep you posted on it. I know our Ford pickup does the same basic thing when you're running headlights and such. You can actually see the voltmeter drop, and hear the blower motor slow down when you come to a stop and start idling. I think some of it has to do with the "turn on" rpm of the alternator, but I really don't know for sure. Anybody else have any input?

-Paul

 

Considering the load as you describe and at idle, it's normal. Alt's don't put out max amperage at low rpms (idle).
If you're cooking alternators, make shure there is a good battery to block ground and good block/batt to chassis ground. There is a ground strap from the back of the block to the chassis, if it's bad/broken, it will put undue stress on the charging system. If the battery is bad, same thing. Battery cables... same. Just make sure all your connection are in good shape and you should be fine.
The fans going all the time, you have a band-aid fix to a cooling problem. That's your biggest current draw issue right there.

 

Paul, I'm not trying to hijack your post...HONEST! lol

My battery cables are both almost new. I put them on about 4 months ago along with that Powermaster alternator. I already checked that strap at the back of the engine to the firewall. It's there and seems to be as it should. The only thing that I can think of is maybe the negative stock wiring is too much for the higher draw of the SPAL fans or something? Maybe I should grind off the grounds for the headlights and such again, and put some heavier guage wire in. I don't know...I just feel the frustration coming on.

 

i have thatproblem, it doesnt really bother me. i turned the idle up a little bit and 700rpm, and also have a 140amp powermaster alternator. the problem only happens when, my radio is bumpin, my headlights, while i have the turning signal on and braking. will it now drop below that 13V mark.

140amp powermaster alternator
march power and amp pullies
700rpm idle
red top battery(this really helped out the pronem)

i had a cheap $49.99 battery in my car, when i first bought the carand it would die really easy onme and i just got really fed up with it. so i bought a red top battery. and the problem isn't relly as bad, as it was b4.

 

Remember something basic about alternators, the higher the output the LESS charging current you have at idle. Especially if it's a modified alt. Unless the rotor is larger with more windings these 140 amp modified units take a bigger nosedive at idle than say a 65 amp unit would. Also, there is a point at low rpm with all accessories on, especially the rear defroster that the alt simply turns off. When the sense wire sees a certain voltage at the low end it will turn off the alt to protect itself. The reason is that the alt cannot supply for any length of time the current to run all the electrical components without overheating the rectifier package. At that point you run strictly off the battery until you come off idle. Look at the range of the guage before you see the red zones, ever wonder why it is so large? Clean connections are always a must, but what I see described here and in other posts is normal for a CS-130 unit. I just picked up a "D" version of the 130, with reclocking it shoud fit in my 89. They have a different charging curve and I am going to see how it compares to the one I have now. I'll post it when it's done. I have 2 different units for my car now, a modified "iceberg" 140 amp and an actual CS-144. The 144 is the best but with everything on at idle the tach still moves somewhat to the tune of the turn signals.