You think I would have learned my lesson about one-wire alternators, but on my 351W build (in a 1967 Cougar with AOD), the shop put a new 200 amp Powermaster alternator on the car. In advertising, it’s supposed to put out 130 amps at idle. Unfortunately, it’s not running at all at idle. To compensate, the shop warned me that the idle was a little high.
All seemed fine until the weather started warming up (80f up from the 50s). Suddenly the car was starting to run hot and when I turned it off, it would diesel and then belch carbon-smelling smoke out of the alternator.
I borrowed a tachometer from a friend in our club was astounded to find out the hot idle was at 3500 rpm. I started turning down the idle, but that also turned down the voltage on the alternator. It won’t excite and start charging below 2500 rpm. By the time you get down to 2000 rpm, the alternator doesn’t even try when you’re in gear with your foot on the brake. Sometimes the alternator will stay excited, although you can watch the voltage drop from 14 volts to 12.5 volts where the voltmeter bounces around for 30 seconds or so before just dropping to a steady 12 volts, no longer even pulsing with the engine, which I assume means the alternator has completely turned off.
Sadly, the spring-summer-fall Houston driving experience is mostly creeping stop-and-go traffic in miserable heat – even at night. The electric cooling fan runs pretty much 100% of the time and the AC blower is always on.
I’m investigating two possibilities:
The alternator to engine ground wire is much smaller than the power cable and hooked to a bolt holding the housing together instead of the M8 size ground hole in the back of the alternator. I would think a ground is a ground, but I’ll still spend $20 to put a big ground strap on there and test if it changes anything.
I’m also using a CVF Racing serpentine pulley kit, and there’s a slight chance that the alternator pulley is an underdrive pulley even though it states nothing about that in the materials. I have an email in to CVF to see if they can tell me what the exact ratio of that pulley is.
While I’m waiting to hear back from Powermaster and CVF, does anyone have any other troubleshooting tips?
Powermaster has good installation instructions on their website. One key item I recall from my 2017 install was how critical ground wire connections and wire gauge was to ensure proper operation. I’ve been happy with my 130 amp Powermaster one wire alternator operation. I don’t have AC but do have dual electric fans and fuel injection with electric fuel pump. The one wire self-exciting types do require 1000-1200 RPM at the alternator to start charging but are designed to continue charging below that RPM afterwards.
Do a rough measurement of the crank pulley and the alternator pully to check how much faster the alternator is turning. I haven’t measured any lately but I would think it would be 2 - 3 to one. That suggests that the alternator is turning at least 5000 rpm to start generating voltage.
Any time I see metric specifications for old American car parts I run away. The alternator should be very well grounded through the case. The engine however might not be well grounded to the chassis. Use a jumper cable to ground the engine to the negative batter post and see if it makes a difference.
I agree with doing a rough measurement of the pulleys. Measure the diameter of the crank pulley and the diameter of the alternator pulley. Divide the crank by the alternator and should get 2:1 or 3:1. If I have my math right, the higher the number the better. At idle (800rpm) the alternator should be turning at 2,400rpm for 3:1. Side note, with 3:1, you won’t exceed the alternators 18,000 limit. For instance, if the engine is turning 5,000 rpm, the alternator will be doing 15,000 rpm
I followed this story for recommendations. I’ve been running a 100 amp Powermaster alternator on my 351W using a homegrown modified serpentine belt system and pulleys off a 5.0 88 Thunderbird. It runs a full MSD ignition system, electric fuel pump, full blown stereo with two amps, and even Vintage Air. I’ve NEVER had an issue since installing this set-up in 2003, but I wired it up as a three-wire charging system and it idles at 800 rpm easily.
Agreed. No problem with my powermaster 1wire either. Very rarely to I need to bump the idle to get it to start charging and once its charging it stays charging even if the rpm drops. Even if do need to bump it its a small bump like 1200rpm. No where near 2500 like your mentioning. Even if its not charging right after startup I have enough battery to keep up until I start to drive it so I dont have to pay attention to the voltmeter all the time.
Which alternator do you have? The Ford 1 wire they offer only goes up to 150amp which closely resembles the factory alternator. If yours is a 200amp then it must be a 3G style which is a little bit different then a true 1 wire. The 3G appears to be able to operate as a 1 wire with how they wire it but not sure if that differs from the one Im running or not.
If that shop set your idle at 3500 to keep the alternator charging I question their knowledge on the subject. You mentioned the pulley being different so I would definitely check on that as it can have a large effect on how the alternator operates. Also make sure its not slipping on the shaft and or the belt is slipping. I have to get mine really tight as to not slip the V-belt.
Make sure all your wiring is up to speed too. With a 150-200amp alternator the factory battery cables are not going to cut it. You need to make sure you have large enough cables with good connections. Make sure you have everything grounded as well. Alternator to block, block to battery and body, battery to body etc. Im running dual electric fans, AC, Sniper EFI etc and I have plenty of power
I guess I just don’t worry too much about fastener sizes-SAE vs metric-as the OEM’s were playing mix and match when I was young. I’ve got plenty of metric tools on hand.
Im using metric battery termials from a modern ford on mine!
I think what Bill is referring to is if the part is a replacement for classic American car and using metric sizing there is a high change its a cheap generic/universal style part and may not be a direct fit or high quality part. In this case its a little different I think since he is using a 3G alternator. Those where pretty common on 90s era fords at a time when metric and standard hardware was in use.
Those pulley sizes are pretty ridiculous, There’s no free lunch - power is power. Electric fans are not more efficient than mechanical fans, they are far less efficient. I think you need to get the pulley sizes right and then fix all the other problems that you have.
Electric fans are as efficient or even more efficient then a clutched fan if you have them properly setup to run as needed. PWM and temp controlled being key to electric fans. A fixed blade type fan is terrible compared to a electric or clutched fan setup.
Most do not think about electrical power from the alternator is transmitted into loss of hp when that alternator is running full tilt trying to keep up with the load. Much like a fan clutch running engaged or not. It takes HP to turn the alternator enough to generate power. the more load you create the harder it has to work.
