Correctly sized alternator?
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From: Sonoma, CA
Correctly sized alternator?
On my '76 F250 SC 2WD with 460/C6 I only have a 40 amp alternator. My truck has CC, and AC. Is this too small for this truck? My voltmeter is showing right around 12vdc when the AC is on. I can see that the requlator is doing its business when I turn on lights and accessories but I'm concerned about the low output (only 40 amp) of the alternator for this size engine and truck. I also have a hot start problem and I'm wondering if this is contributing to it. When it's hot it turns over real slooooooow but when cold it turns over normally.
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Joined: Feb 2006
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From: Sonoma, CA
When I run the AC at idle, the aftermarket voltmeter in the truck will only read 11.5 or so volts. If I get the rpm's up to about 1500 with AC it will rise above 12 volts a little. My timing is 12btdc. I guess the battery could be the culprit or overheated starter. Does the starter need a heat shield? A load test on the battery should eliminate that or determine it's condition. With the AC off at idle I am around 13 to 13.5 volts. Maybe I should get out my Fluke and do some real voltage readings. I just got rid of the aftermarket Ammeter in the truck that was passing ALL of the charge current from the alternator into the cab and back to the battery. Yikes. So I am working with the new voltmeter to get some baseline reading under different conditions.
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Try 8-10° BTDC. Follow the directions in the service manual for timing your engine.
When wired properly the OEM DS-II ignition module has a start retard circuit built in that works well. Aftermarket ignitions do not have that function.
Low voltage at idle is normal. You should get full voltage at ~2000RPM.
Charge voltage at the battery should be 13.8-14.2VDC @2000RPM with a fully charged battery.
Use the Fluke meter.
When wired properly the OEM DS-II ignition module has a start retard circuit built in that works well. Aftermarket ignitions do not have that function.
Low voltage at idle is normal. You should get full voltage at ~2000RPM.
Charge voltage at the battery should be 13.8-14.2VDC @2000RPM with a fully charged battery.
Use the Fluke meter.
Last edited by Torque1st; Jun 7, 2006 at 10:21 PM.
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I was also concerned about a stock 60amp alternator (on my '78 F100 with 6-inline engine) when I added fog lights and a decent stereo system (including a 80amp amplifier). So I upgraded to a 100amp alternator (offered as an option on 1978 trucks). I bought it new (Bosch brand) at Pep Boys and installation was straight forward, except changing some terminals for the wires and using a slightly larger belt. That and a red top Optima battery give some peace of mind. Raul
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There is a different Voltage regulator that goes with that HO Alternator.
It is listed in the Van (e-series listing)
It is listed in the Van (e-series listing)
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According to Napa and Autozone, all Ford alternators they sell use exactly the same voltage regulator (I cross-checked this in all engine configurations: 300 to 460ci). I did put one of these "new" voltage regulators (has some electronic improvements according to the included instructions) when doing the swap to the 100amp alternator. After a month of use everything is working just fine. I have to add that I did my research in these forums as well as in fordsix dot com before I did my swap. Raul
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You know, I just went in looked in my Motorcraft application book and you are absolutley right.
All this time I was reading one line up which showed a GR748A VR.
That application is actually for the 75 amp Bronco .
I will now stop telling people they need a different one for the 100 amp + alts.
Sorry everyone from before
Thanks for bringing me in the know
All this time I was reading one line up which showed a GR748A VR.
That application is actually for the 75 amp Bronco .
I will now stop telling people they need a different one for the 100 amp + alts.
Sorry everyone from before
Thanks for bringing me in the know
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From: Louisville,Ky.
My 77 with a 460 has no cc, a/c just an am radio and I installed the 100 amp alt when I installed the 460 from a Lincoln Mark V. It's a bit overkill, but great for charging dead vehicles for a few minutes before jump starting. Just hook the cables up and give it 10 minutes and start-em up. This helps keep from over straining the charging system of the dead vehicle if they just left the lights on or something and the charging system is in good shape to begin with.
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Don't try charging a dead battery with any of the new high amp small frame alternators. They are rated like consumer vacuum cleaner and compressor motors. They will put out the full amperage for about 1 second before they toast something. The old large frame alternators we have on these old trucks will put full amperage out for several minutes before they fry. Automotive amp ratings are far different than industrial equipment ratings.