Alternator sizing
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Joined: Nov 2023
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From: Vegas, baby!
Alternator sizing
I have a 1973 coupe with A/C and auto trans. A prior owner had replaced the original 61 amp alternator with an 80 amp chrome job (probably from Jeggs?). I don't know if the replacement was done just to get a shiny chrome part, or if it is because the car has electronic speedo and tach. Or both. In any case I'm restoring the car to original and just bought a correct numbered and date coded 61 amp unit.
Here's my question. Would it hurt anything to install the 61 amp alternator now and leave the electronic speedo and tach for a later date? Let's say I'm driving home from a car show at night with the A/C on (very likely to happen out here in the desert). Will bad things happen?
Here's my question. Would it hurt anything to install the 61 amp alternator now and leave the electronic speedo and tach for a later date? Let's say I'm driving home from a car show at night with the A/C on (very likely to happen out here in the desert). Will bad things happen?
Race Director
Joined: Oct 2008
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From: Long Island
the 61 will work as long as you have the original headlights or LED that pull less amps.
The key is to watch the draw when it rains and the wipers are on with the A/C at a stop light or stop and go traffic. .
I drive my stock 72 with A/C all the time. Since its an auto, do what I do and sometimes put it in Neutral if I'm stuck in heavy traffic - that helps at stop lights and traffic.
The key is to watch the draw when it rains and the wipers are on with the A/C at a stop light or stop and go traffic. .
I drive my stock 72 with A/C all the time. Since its an auto, do what I do and sometimes put it in Neutral if I'm stuck in heavy traffic - that helps at stop lights and traffic.
Pro
Joined: Nov 2023
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From: Aubrey TX
Its fine. Back in the late 80's I had a 71 Mustang with AC, a 55 Amp alternator and 3 audio amps that pulled 30 amps (at peak) and had no problems in general. However to offset the high load I used the highest capacity battery that would fit. Drove that car for 5 years and only got stuck once where it wouldnt start.
Pro
Joined: Nov 2023
Posts: 676
Likes: 328
From: Aubrey TX
the 61 will work as long as you have the original headlights or LED that pull less amps.
The key is to watch the draw when it rains and the wipers are on with the A/C at a stop light or stop and go traffic. .
I drive my stock 72 with A/C all the time. Since its an auto, do what I do and sometimes put it in Neutral if I'm stuck in heavy traffic - that helps at stop lights and traffic.
The key is to watch the draw when it rains and the wipers are on with the A/C at a stop light or stop and go traffic. .
I drive my stock 72 with A/C all the time. Since its an auto, do what I do and sometimes put it in Neutral if I'm stuck in heavy traffic - that helps at stop lights and traffic.
Le Mans Master
Joined: May 2003
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From: Fernandina Beach FL
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As far as additional load of the electric speedo and tach- that is very minimal-probably less than 1A-no worries at all.
The 61A correct alt will work fine- as long as it is correctly rebuilt and indeed does put out the rated amount of current. Just a guess- that chrome 80A might
have made 80A OGD (on a good day!!!)
Also note the 61A alt's max output is at about 1800RPM- not at idle. So sitting in traffic would be the issue- not driving down the road,
Richard
The 61A correct alt will work fine- as long as it is correctly rebuilt and indeed does put out the rated amount of current. Just a guess- that chrome 80A might
have made 80A OGD (on a good day!!!)
Also note the 61A alt's max output is at about 1800RPM- not at idle. So sitting in traffic would be the issue- not driving down the road,
Richard
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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with the two above post's.
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