Alternator/voltage regulator issue?
- Thread starter JNewm
- Start date
kmead
Old enough to know better
Because integrating it into the alternator meant a reduction in parts, a reduction in wire and a reduction in installation labor. Additionally it removed multiple connections which could fail in the field and make it difficult to diagnose and resolve the problem.
Regulators moved internally almost exclusively in the early 70s.
Fewer parts, less stuff to keep in inventory and source so more profit and higher reliability. A win all around.
tvmaster
True Classic
As long as the tubes are clear
Dan Sarandrea (Phila)
Waitin' On Parts...
A friend of a friend needed help changing something under his 928, so I volunteered to learn about 928s.
Found that his 928's alternator had a conceptually identical setup, a (sort of rubberized) hose assy that ducted cooler air into the back of the quite large BTW alt. Got this pic of the 928 setup from Google:
Found that his 928's alternator had a conceptually identical setup, a (sort of rubberized) hose assy that ducted cooler air into the back of the quite large BTW alt. Got this pic of the 928 setup from Google:
Dr.Jeff
True Classic
Notice the differences between it and the one on the X. The hose is much larger diameter, the transition from the hose to the rear cover is smooth and more radiused, the space behind the alt inside the cover is greater, and that hose is fed from a direct air source at the front of the car - with a lot more air volume and much cooler temp. All of these subtle differences will make a huge change in how much air it actually passes through the alt.
tvmaster
True Classic
So I got the powered subwoofer installed with the 33a Bosch. So far, the car keeps starting. It has a 15amp internal fuse, and a 40amp inline fuse between the battery and the unit. I’ll still upgrade to more power, but the headlights, blower and stereo all work together. I’ll have to try it at the local shop where they can measure the load properly. Still have some wiring management to work out, but otherwise, sounds good…
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tvmaster
True Classic
Mr kmead... I was just about to upgrade from the 33a Bosch to either a 55a Marelli or a 61a Bosch. Both are available, but the Marelli may need rebuilding.
So, I call a local 'expert' rebuilder found on Yelp with 5-star ratings en masse.
He goes a little nutty on the phone, saying Youtube and web people know nothing, and that increasing amperage on a car not meant for it will always cause overheating at lower RPM's and will continually burn out the 'stators'.
He got downright cranky about it.
Essentially, I was calling to ask about price estimates for rebuilds, instead, I got a lecture on how adding stronger alternators was a certain path to total destruction. He also claimed to be a 'Certified American Master Mechanic' of 40 years. If that's a thing.
Thoughts? Is he correct? Is it certain suicide to put in a stronger alternator? Matt didn't think so, nor do most people found here.
Now I'm right back at being confused, lol.
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jimmyx
True Classic
I think the word is "certifiable"....
tvmaster
True Classic
so you have doubts about his claims of certain death to alternators? I tried nicely to assure him the higher amp units were from later year cars of the same models, but to no avail. Low RPM's meant DEATH! Death to stators! (I had to look that up, so I learned something today)
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Dr.Jeff
True Classic
Goes to show what Yelp knows. I've never placed any trust in any of the internet reviews - people are idiots. He is completely off base.
kmead
Old enough to know better
Anytime I am faced with someone like that vomiting out a tirade its yup yup, click.
The battery in your car can be any amperage you want to buy, neither the car or the alternator care. The starter will care when it comes time to start the car.
The alternator doesn’t know what alternator was in place before it. If you choose an internally regulated alternator it won’t care about anything beyond is it maintaining the 14.2v it is designed for against the load you are imposing use switches and replenishing the battery after a starting sequence.
You don’t need to go to an alternator which will have too much capacity beyond what you need. The reason for this is a high capacity alternator (ie 120 amps like the bumpity bump crowd needs for their stereo) will consume more power from your paltry 67 hp motor when it is engaged and will constantly be ‘short’ cycling. An alternator in rough balance with the actual energy load of the car plus a bit to recharge the battery is what you are trying for.
So, a 55 amp alternator will be just fine for your car with your current accessories. The AC cars have a bigger alternator because the energy used by the second fan running and the ventilation fan means the car consumes more power and thus the alternator needs to be 65 amps. Yes the 55 amps is much more than what your car came with but you are also pushing a stereo (which was not on the Italians list in 1973) and a amp to drive a sub woofer (the Italians didn’t even know what one of those was in 1973 when the car was finalized for specifications).
Anyway step past the lunatic on the phone and just effing buy a functioning alternator and put it in.
You can ignore me as well as I am a effing lunatic as well…
tvmaster
True Classic
New alternator installed yesterday, 61a Bosch rebuild. And yes, external parts mean things break. PO, likely the WD team, bundled up the wires in the engine bay in a way which caused the old, G light wire to break when unbundled. Took a while to trace that mess (remove instruments to test bulb, etc.) to discover the old, broken wire.
Now reading 12.5 volts charging with everything turned on.
Now, let’s see if the battery will live on….
ng_randolph
Bjorn H
If, properly measured, you are only seeing 12.5 V, then the charging system is not working. If you are measuring this at idle with all loads turned on, then perhaps there is hope. A 61 A (<capital "A", not lower case) alternator is not able to deliver 61 A at idle. I would go through a few more tests:
1. When the ignition is off, is the "G" light on? It should not be.
2. Turn the ignition on (but do not start the engine). Is the "G" light on? It should be, and if it is not you need to find out why.
3. Start the engine and let it idle for, say, a minute. Then rev the engine to 3000 RPM and hold it there for, say, 10 seconds. Does the "G" light turn off? It should.
4. With no electrical loads turned on, measure the voltage at the battery while keeping the engine at 3000 RPM. What voltage do you see? It should be very close to 14 V.
5. Turn on headlights, rear window defogger and the heater fan. Measure the voltage again, engine at 3000 RPM. What do you measure?
At 3000 RPM the alternator should be able to deliver most of its rated current, but there is no magical threshold at 3000 RPM.
1. When the ignition is off, is the "G" light on? It should not be.
2. Turn the ignition on (but do not start the engine). Is the "G" light on? It should be, and if it is not you need to find out why.
3. Start the engine and let it idle for, say, a minute. Then rev the engine to 3000 RPM and hold it there for, say, 10 seconds. Does the "G" light turn off? It should.
4. With no electrical loads turned on, measure the voltage at the battery while keeping the engine at 3000 RPM. What voltage do you see? It should be very close to 14 V.
5. Turn on headlights, rear window defogger and the heater fan. Measure the voltage again, engine at 3000 RPM. What do you measure?
At 3000 RPM the alternator should be able to deliver most of its rated current, but there is no magical threshold at 3000 RPM.
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tvmaster
True Classic
yes, measured at low idle parked. Will set up a higher rev test today. At low idle with nothing turned on, was reading 13.5v solid.
The install problem was the wire feeding G broke during install. Got it rectified.
kmead
Old enough to know better
Congrats on the upgrade! Sorry it was a bit more than involved but that is the way it is with old cars and the gain of knowledge by doing
tvmaster
True Classic
lol, yeah, Mr. racer/tech was a tad pissedCongrats on the upgrade! Sorry it was a bit more than involved but that is the way it is with old cars and the gain of knowledge by doing
tvmaster
True Classic
Oh, and another funny thing: in the WD episode, it is clearly video taped and noted that the alternator was removed by them. Guess what we found yesterday - they either forgot, or lost one, but the old alternator had been held in by only ONE bolt since we bought it.
Ooops.
Ooops.
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