I've got a `65 Skylark with factory a/c. I've also added an electric fan along with MSD, electric fuel pump, etc. I upgraded to a rebuilt alternator built to put out 100amps. I have an Autometer voltmeter in the car and under normal circumstances it read around 14 volts. However, when I turn on the a/c, which here in Florida is most of the time, the voltage drops to around 13 until the engine rpm is above 1500 and then goes back to 14, but when the fan kicks on it drops to just under 12 volts and eventually will run the battery down. The fan is rated at 18amps. I seems that the 100amp alternator should do the job well but apparently it isn't. I still have the external regulator on the car that I have replaced with a new one. I could go back to the clutch fan and eliminate this problem but I'd like to keep it mainly because when I'm in traffic it will have some airflow through the a/c condenser, otherwise he a/c temp goes up. Is it possible that the regulator isn't up to the challenge? Any suggestions would be greatly appreciated. Thanks. Bill
I think you need a bigger alternator. Don't think the 100 amp is enough. 18amps is a big draw. I'd say you'd be ok with pulling around 11 or 12 amps from the fan. What fan set up do you have? Link?
Two things to look at that I can think of. The first thing to look at is the size of the wire coming from the alternator. If it's too small it will just create heat and not provide full charging ability. I'd have atleast 10 awg if not 8 awg to the alternator to the stud on starter. 2nd thing. If you have a 100amp alternator that's been rebuilt (think autozone piece) the air gap between the rotor and stator may be too great (both have been machined to be cleaned up) this will significantly decrease the output of the alternator.
The fan is a Flex-a-lite Extreme S-blade, complete with a shroud that fits the radiator perfectly. Bill
The alternator was built by a reputable builder who has been doing it all his life(the only stuff I buy at Autozone is polish or hand cleaner). I've used his services for 20 plus years and never had a bad product. Still, I'm wondering if I should have it tested just to be sure that it is actually putting out 100amps. Bill
Perhaps you can go back to where you bought the alt. and have it load tested? Prev. poster made a good call w/ the wire size.
The wiring is original, which I suppose should be upgraded anyway. After all, it's 44 years old. Thanks for the suggestion. Could I run a separate temporary 8ga. wire to the starter post just to see if it helps? Or even straight to the battery since it connects to the positive cable at the starter, anyway? Bill
Yea for a dirt simple test, just run a temporary large wire from alternator post to the battery with the other wires still connected (you could make it permanent too but not sure how tidy your keeping your wiring. The starter is one of the best place to connect more wires to. Just make sure to add fuses to your loads). You maybe able to do it with half a jumper cable but you may have trouble getting a good connection on the post on the alternator. While your at it, also check for a good connection at the battery to engine ground, and body to engine ground. also make sure your supply line to the fan relay is going to a very solid source. If it is pulling 18 amps you will need to run that to a large added connection (your factory fuse panel will NOT be able to handle that extra load) EDIT: this assumes your 100amp alternator is an internally regulated unit.
Upgrade to a 12SI alternator with integrated regulator. I think the old style regulator is causing a bottleneck. It's very easy. You should run relays on your high draw accessories too... as mentioned before, your stock wiring is undersized for the accessories you are running.
Thanks, I'll give it a try. The supply line comes directly from the battery, and I have more ground straps on the car than I need already so I doubt if that is the problem. I noticed you're in Milwaukee. I'm originally from the Beloit/Janesville area and was up there visiting family 2 weeks ago and brought the `65 along. Made it to Union Grove while we were there and got to race with the Chicago Gran Sport club because a friend of mine belongs to it. Had a ball. Thinking about moving back. My wife hates the cold winters but I hate Florida. Gotta wonder who's going to win that one :-( Bill
EDIT: this assumes your 100amp alternator is an internally regulated unit.[/QUOTE] Nope, the original style external regulator. Bill
Remember when an alternators amperage is rated,it's at max rpm's,perfect temperature & conditions.Just like dyno HP ratings. You could also go with a smaller alternator pulley to spin it quicker at idle.
Something to try is to be sure of the volt meter accuracy. Try testing the battery voltage, at the battery, using a digital volt meter. Then check the voltage when the fan comes on. Next, turn the A/C on, again checking the battery voltage. These tests should be performed both at idle and at about 2000 rpm. One other thing to check if the battery voltage is low is to check for a voltage drop between the alternator and the battery. Let's take this one step at a time. Knowing what is wrong is essential to fixing it. Throwing tools and parts at a problem only adds to effort and expense. Ray
To begin, I installed an 8ga jumper wire between the battery and the alternator. That didn't seem to do much so I went with a 6ga wire. The following readings are with that 6ga wire installed and checked with a digital multimeter, and all readings coincide with my voltmeter readings. Idle...everything off 14.2 2000rpm...everything off 14.2 Idle...a/c on 12.6 2000rpm...a/c on 14.2 Idle...fan and a/c on 11.9 2000rpm...fan and a/c on 12.5 Idle...alternator to battery 14.1 2000rpm...alternator to battery 14.1 Bill
Like I said before, your stock charging system is not designed to produce enough amperes for your accessories. To do it right, you need to convert to a 12SI alternator and set up a second set of wiring using feeds from the battery and soleniod for power, and relays with all new correctly sized wiring for your high draw accessories.
Just a reminder to everyone - when you increase the amperage output capability of your alternator, you have to increase your wire size! Putting more amps through a smaller wire can cause a fire. -Bob C.
If you run electric fans, fuel pumps etc a stock alternator is not up to the task. Run an SI or CS series Delco. It is better to run them as 3 wire not one wire. SI setup: 1. From main post on alternator run a 10 guage charging wire to the main starter post. 2. Run a short 12 or 14 guage wire from the main post on the alternator to the + 12v plug on the alternator. 3. Run a 14 guage wire to a 12v switched source to the other plug on the alternator. 4. Run an 8 guage wire to a terminal block from the main post on the alternator. USE THE THE TERMINAL BLOCK TO POWER YOUR FANS. If need you can have a second terminal block in the that has its own 8 guage wire from the main post on the alternator. For anything that likes full voltage I use relays. Use the terminal blocks as the voltage source and the wiring harness as the source to switch on the relays. This will give you 14V at whatever you want to run. The CS series alternator are a little harder to wire. You need to use a 35 to 50 OHM resistor in the exciter wire (switched source) if you are not going though the dash light.
You could look into installing the M.A.D electrical kit in your car. It comes with everything you need to re-do a good portion of the charging system.
1) With air conditioning, you should run a mechanical clutch fan. They pull air much better than an electric fan. If you STILL need more fan, then add an electric. But usually you don't. 2) There is a "remote voltage sensing" capability with your alternator. Learn how to do it from MAD electrical. This can dramatically improve your whole charging system. 3) Sounds like your A/C compressor is drawing a lot of current. If youare alternator can maintain 14V with the fan running, your A/C compressor shouldn't be the thing that drags the voltage so far down. I suspect, however, that if you change your "remote voltage sensing" (#2, above) you'll see this go away. 4) Where are you measuring your voltage? In the cigarette lighter? 5) Get some terminal blocks from MAD electrical, especially for your fan. Where do you actually get power for your fan now? Fusebox? The battery? 6) Is it time for a new engine harness anyhow? They are only a couple hundred bucks, take 2 - 3 hours to install (pretty easy actually), and dramatically improve your car's reliability. And at the same time, you could increase the wire size from your alternator (you might be able to buy a custom-modified harness for short money, many of them are made to order, ask about getting a larger alternator wire). I suspect that 100 amps is more than sufficient to run your 18 amp fan and your 7 amp fuel pump. Some some or all of the above and you'll be running good. -Bob C.
