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Alternator Conversion Issue

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MikeAH100M

MikeAH100M

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I recently converted from a generator to an alternator on my 100M using the Lucas Kit from AH Spares. Everything tested out OK on installation but after driving for several hours, the car died and would not turn over. The battery was dead. I had the battery tested and it was fine and it held a strong charge. I tested the alternator output and it was 13.5v. However, when I loaded it up (turned on lights and the thermostatic electric fan kicked on) the output at the battery was only 10V. Looks like the alternator can't handle the load. I contacted AH Spares to check on a remedy but wanted to check with the Forum to see if there were any suggestions. The electric fan has been a godsend on engine temp so hate to delete that. Not great at this electrical stuff so suggestions appreciated.
 
The electric fans draw a huge amount of power. Although it doesn't look original, I had to install a 105-amp AC Delco alternator when I installed my AC and electric fan.
 
It’s the amperage that matters . What size alternator did you use (Amps) most of the kits are 45/50 amps but Ahead 4 Healeys offers an 80 amp alternator . That’s the one I used on my BT7 with all my rally lights and goodies on .
You’re probably going to have to either delete you fan or put a bigger alternator on .
 
Thanks all. That's what I thought I would need to do. I'll check the amperage on the current alternator and see about a replacement.
 
Think of it this way . Voltage is just the carrying device (legs) amps are the muscles . You need more muscles (amps) to carry more weight (electrical load) lights , fans , AC etc
 
My search for higher output generators from Healey sources showed that they all fit BN4's and later, nothing for BN2's. I'm checking with the supplier to see the reason. Fitment shouldn't be an issue - they are all made by WOSP which is the 45A that I currently have installed and brackets look to be the same. Anyone know of other reason why they wouldn't work on a BN2?
 
If you want an idea how many amps an electric fan draws, I tried to start my BN4 with the electric fan running. It wouldn't turn over. I had to shut the fan off to get it to start.
 
I have a 70 amp alternator on my 100 which easily handles all lighting and a 12" fan rated at 80 watts which converts to 6.5 amps.
 
Last edited:
BobHaskell said:
Michael,
Did you go to a heavier wire with the increased amperage?
Click to expand...
My 80 amp alternator is hooked up to a standard replacement harness , no issues .However , I haven’t driven the car at night with all the lights on and the heater etc etc etc running so not pulling full load on the electrical system .
 
I left the standard harness in place, just added a 4 ga. cable from the alternator output to the post with the cable from the battery. Probably overkill, but it's what I had on hand.
 
Michael-Check that the generator warning bulb is installed, not burned out, or an LED bulb. The original system needed an excitation voltage from the generator lamp circuit to turn on the charging system. You must use a tradition incandescent bulb in the generator warning light circuit. I have seen this condition before, and the owner had an LED bulb installed and his alternator would not charge the battery. As soon as we replaced the LED bulb with an incandescent bulb problem solved.

feel free to reply should you have any questions.

Peter
 
The dynamator on my BT7 (purchased from AHSpares) is also rated at 45A. My charging voltage is 14.5V vs your charging voltage of 13.5V. I also use a SPAL pusher fan rated at 6.5A. My voltmeter doesn't show any drop with the fan on.

Have you had your alternator tested off the car? Did you switch pulleys on it? My dynamator came with a smaller, friction fit pulley requiring a new V belt (15425). Do you have a good ground? I cleaned up the interface between the dynamator and the mount, but also ran a separate heavy gauge wire from the alternator body to the chassis.
 
BN6_L1232 said:
Michael-Check that the generator warning bulb is installed, not burned out, or an LED bulb. The original system needed an excitation voltage from the generator lamp circuit to turn on the charging system. You must use a tradition incandescent bulb in the generator warning light circuit. I have seen this condition before, and the owner had an LED bulb installed and his alternator would not charge the battery. As soon as we replaced the LED bulb with an incandescent bulb problem solved.

feel free to reply should you have any questions.

Peter
Click to expand...
Thanks, Peter. I checked and the bulb is installed and working and not an LED. Very interesting condition.
 
JoeCA said:
The dynamator on my BT7 (purchased from AHSpares) is also rated at 45A. My charging voltage is 14.5V vs your charging voltage of 13.5V. I also use a SPAL pusher fan rated at 6.5A. My voltmeter doesn't show any drop with the fan on.

Have you had your alternator tested off the car? Did you switch pulleys on it? My dynamator came with a smaller, friction fit pulley requiring a new V belt (15425). Do you have a good ground? I cleaned up the interface between the dynamator and the mount, but also ran a separate heavy gauge wire from the alternator body to the chassis.
Click to expand...
Thanks for the ideas. I'm working on getting the amp rating for the RevoTec fan I installed. I haven't tested the alternator off the car, but that will be a next step.
 
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