[torqhead]

I put a 94 Amp alternator on the car to do some testing. I had the alternator tested at the auto parts store before taking it (they showed it charged at 14.7v). After installing it I started the car with no electric choke or fans running. Effectively HEI, electric fuel pump with their associated relays energized were the only items running, voltage showed 14.2 at 1100 RPM (engine cold). Added electric choke, no change, still at 14.2, added electric fans and voltage dropped to 13.8. Let the car warmed up and then turned on A/C, voltage dropped to 13.3 as long as I kept the RPM up, if I revved to 3000 or so I could get the voltage up to 13.8 but at idle voltage dropped to 12.8. Also checked temps on the casing of the alternator as I went through this process. With the A/C on and revving the motor to 2500/3000 the alternator temps increased and got upwards of 190+ degrees.

Car sat overnight and pulled another test. Battery showed 12.4v, started car again (1100 RPM)with no electric choke or fans, voltage was at 13.4. Added choke, no change.. Added electric fans and it dropped to 13.3 as car warmed up it dropped to 13.15. Car going to idle 800 RPM, the voltage dropped to 12.8. Thinking the addition of the A/C the previous day damaged the alternator.

Did some research and it looks like the Sanden alternator uses 49 Amps of power, validated the coil is within tolerance on the Sanden at 4.1 Ohms (acceptable factory range is 2.8 to 4.4 Ohms).

I think my power requirements are greater than what the alternator can produce, but don't know enough about the other components and what they require for power. Any suggestions on what's the best way to figure this out?

[george kujanski]

The Sanden COMPRESSOR probably uses 4.9 Amps, I doubt it uses 49 Amps.

The big loads you have are the fans, the A/C system (clutch, blower). These will be the majority of the electrical loads.

If you have the specs on the fans, that will give you some data.
A better way would be to get a clamp-on DC current meter to measure the load current on each of those loads, add them up, and compare to the alternator spec, if you have it. If it's a Delco, the output curves are available as seen in the previous post.

For the user that needs a ballpark estimate, I'd say if the car has electric radiator fans, a Delco 12SI 94 A. is a good starting point....about 50+ amps at most engine idle speeds and a drop-in install.

My Caddy had 2 fans, A/C, etc. and came with a CS144, 140A, but it's not a drop-in install on our older Pontiacs.

George

[torqhead]

Originally Posted by george kujanski

The Sanden COMPRESSOR probably uses 4.9 Amps, I doubt it uses 49 Amps.

The big loads you have are the fans, the A/C system (clutch, blower). These will be the majority of the electrical loads.

If you have the specs on the fans, that will give you some data.
A better way would be to get a clamp-on DC current meter to measure the load current on each of those loads, add them up, and compare to the alternator spec, if you have it. If it's a Delco, the output curves are available as seen in the previous post.

For the user that needs a ballpark estimate, I'd say if the car has electric radiator fans, a Delco 12SI 94 A. is a good starting point....about 50+ amps at most engine idle speeds and a drop-in install.

My Caddy had 2 fans, A/C, etc. and came with a CS144, 140A, but it's not a drop-in install on our older Pontiacs.

George

Yeah, I misquoted on the Sanden as it uses 49 watts of power. Curious with the drop I've seen in voltage output between the first and second time running the car if that's pointing to the fact the alternator was damaged?

[george kujanski]

One thing: it depends where you measure the voltage....on a 3 wire system, the alt is controlling the battery voltage and it's different than if you measure at the alt output stud.

A one-wire will try to keep the alt output stud at a 14.0 volts, but if you measure downstream in the harness the voltage will be less due to voltage drop in the cabling, i.e. the greater the output current, the greater the voltage loss in the harness.

Bottom line: with a 3 wire, measure at the battery, with a 1 wire measure at the alt output to see if the alt is regulating correctly.

George

[torqhead]

Originally Posted by george kujanski

The Sanden COMPRESSOR probably uses 4.9 Amps, I doubt it uses 49 Amps.

The big loads you have are the fans, the A/C system (clutch, blower). These will be the majority of the electrical loads.

If you have the specs on the fans, that will give you some data.
A better way would be to get a clamp-on DC current meter to measure the load current on each of those loads, add them up, and compare to the alternator spec, if you have it. If it's a Delco, the output curves are available as seen in the previous post.

For the user that needs a ballpark estimate, I'd say if the car has electric radiator fans, a Delco 12SI 94 A. is a good starting point....about 50+ amps at most engine idle speeds and a drop-in install.

My Caddy had 2 fans, A/C, etc. and came with a CS144, 140A, but it's not a drop-in install on our older Pontiacs.

George

What year/model Caddy as that will help me look up the part. I don't mind looking at a wiring and mounting mod if required.

[torqhead]

Originally Posted by george kujanski

One thing: it depends where you measure the voltage....on a 3 wire system, the alt is controlling the battery voltage and it's different than if you measure at the alt output stud.

A one-wire will try to keep the alt output stud at a 14.0 volts, but if you measure downstream in the harness the voltage will be less due to voltage drop in the cabling, i.e. the greater the output current, the greater the voltage loss in the harness.

Bottom line: with a 3 wire, measure at the battery, with a 1 wire measure at the alt output to see if the alt is regulating correctly.

George

All test have been done at the battery.

[george kujanski]

Mine was a '93 with 4.9L. My wife has a '98 Eldo with Northstar....same alt. The CS144 is a larger frame unit and typically uses a serpentine belt. It would require a different pulley in a non-serpentine application.

George

[stellar]

The csa144 mount center to center is about 1/2 inch longer and of course it is a bit wider too.
shouldn't be to hard to mount. It can also be easily bumped up to 200 amps with just a stator change with almost no low rpm sacrifice.

[gtofreek]

CS130 = 130mm diameter stator.
CS144 = 144mm diameter stator.

So people can visualize the size difference.

[torqhead]

Thanks for the info guys. What's it take to wire the CS144 in, will it still operate my alt light?

[HWYSTR455]

Yeah, the CS144 is larger, and the mount/swivel lug is wider too. With fixed alt brackets, ones that are beyond like 71-up, it take chopping it up. For the mount/swivel, you have to shave the spacer or the mount/swivel. It's not a bolt on.

CS144 uses the same plug as the 130, and there are readily available adapters (if you don't want to rewire the exiting plug/harness).

Couple things to keep in mind, and I speak from personal experience. I've created a graveyard of cooked alts. George, think you remember some of my nightmares!

Once a belt slips, it's toast, and it just plain needs to be replaced. Any time you put a new alt on, put a new belt on, period. It might look good, and not squeal, but believe you me it won't charge due to slip.

Biggest cause of overheated alts = belt slip.

Tightening the belt. If you over tighten the belt, it will cook the alt bearing, if not the water pump, and in extreme cases, can even cause wear to the front main bearing.

If it's not tight enough, it will slip.

Right around 150a is where the v-belt starts being an issue where it doesn't have enough contact surface and starts slipping. So my guess is your belt is slipping, and why it's not keeping up. Try changing the belt first, but another guess is you're going to have issues no matter what with a 200a.

Charge circuit. As mentioned, you need to check everything there, and for potential shorts too. Upgrade the charge wire to a min of 10ga, if not a pair of 10ga wires. Especially if you're running fans, pump, and a stereo with some decent draw.

The alts I've been running lately are the PowerMaster 47294 alts, which are 12si 150a with the baffled fan. They make their' own, and are metal.

https://www.summitracing.com/parts/pwm-47294

I agree with Quick-Silver and others, read the MAD tech articles.

Spikes/surges. Some may not agree with me on this, but I've proven it in practice. Because of spikes/surges, run a stereo cap, a 1k farad is fine, it will prevent spikes from cooking the regulators. I suggest that even if you don't have a killer stereo but have other loads, like fans, H4s, pumps, etc.

Search here and you will see how long I struggled with this very issue.

Honestly, the best way to exceed the 150a v-belt limit is to go serpentine.

The factory harnesses are marginal at best, you start throwing stuff on there and it fails to provide the required power at a pretty quick rate.

I'm doing the build on the LeMans, and plan to make all my own harnesses. Will use the previous setup as a basis and will share on my build thread. It's basically a step or so further than what MAD did.

.

[PontGuy]

Great thread with very useful and accurate information.

I went through a similar debugging process with my 74 TA a couple of years ago but on a smaller scale since I was not running electric fans, etc. I ended up buying an ACDelco-rebuilt 94Amp 12SI and that took care of my problems since it puts out a lot more at idle than the other stock-rebuilt alternators that fit the car and it has the correct high-flow cooling fan.

One recommendation, already mentioned- invest in a DC clampmeter. They are relatively cheap and buying one helped me tremendously. You can measure the individual and total loads with it and that eliminates a lot of the guessing. Here is what I got and some of it surprised me.

Headlights- 6.5A on red/black wire with original fusible link
Brake lights- 7.8A on black/red wire
A/C blower- 18.3 A on big black wire and at lead to blower
A/C clutch- 2.3A measured on lead to compressor clutch
Radio amp- 1.5A
Coil+ less than 2A
Instruments, etc. hardly draw any load.

Total load for my car with everything running- 39A

Once you know the loads then you will know how much alternator you really need.

[HWYSTR455]

Wow, almost 8a on the brake lights? That surprises me too.

Fusible links can start becoming a resistance over time, comes a point where they should be replaced, some overlook that.

A/C fuse holder sometimes tends to cook, and it too eventually needs to be replaced.

Bosch makes brand new 12si alts, and though Delco lists some as new, they are still rebuilt units. (not sure how they get away with that)

Duty cycle. If your calculated load is 40a, you don't want to use a 40a alt, you need some head room, the alt will last longer that way, and allow for demand needs.

Headlight switches should be replaced at least every 10 years, they can slowly start having more resistance too. If you do the MAD full power headlight mod, this becomes a non-issue.

.

[gtofreek]

Originally Posted by HWYSTR455

Wow, almost 8a on the brake lights? That surprises me too.

Fusible links can start becoming a resistance over time, comes a point where they should be replaced, some overlook that.

A/C fuse holder sometimes tends to cook, and it too eventually needs to be replaced.

Bosch makes brand new 12si alts, and though Delco lists some as new, they are still rebuilt units. (not sure how they get away with that)

Duty cycle. If your calculated load is 40a, you don't want to use a 40a alt, you need some head room, the alt will last longer that way, and allow for demand needs.

Headlight switches should be replaced at least every 10 years, they can slowly start having more resistance too. If you do the MAD full power headlight mod, this becomes a non-issue.

.

I recommend that your total load should not exceed 60% of the alternators rated capacity. At least that's the number we used out here in the desert. For a 40 amp load, that would be a 67 amp alternator minimum.

[PontGuy]

Like I said the ACDelco 94A alternator solved my problem. I assume it was rebuilt to stock specs, unlike the big box store rebuilds that I tried that didn't fix it. Plenty of juice at idle and no problems since, going on 2 years now.

Wow, almost 8a on the brake lights?

Yup, I was surprised by this so I opened the trunk and checked at the bulb wires, and each draws close to 2 amps (x4 bulbs).

My charging system was weak especially at idle, and idling with the headlights on and A/C blower running the engine would sometimes suddenly stall when I stepped on the brakes. I could see the big voltage drop on the dash gauge but didn't understand why the engine would stall... until I found out a previous owner left the resistor wire in place feeding the MSD RTR distributor. Low volts + resistor wire = not enough juice for the MSD.

I expect that radiator cooling fans would add a lot to the overall load. With a clamp-on meter you can check and see exactly how much.

[HWYSTR455]

If you spec the police and ambulance alts they put out at idle.

There are some that provide amp/rpm charts, but I've found that they are not accurate.

.

[HWYSTR455]

Or change the pulley. That's a dance though, because the contact area of the belt is less, so on higher amp alts it tends to slip more.

.

[gtofreek]

Originally Posted by HWYSTR455

If you spec the police and ambulance alts they put out at idle.

There are some that provide amp/rpm charts, but I've found that they are not accurate.

.

Most of those alternators are very heavy duty designs not normally found on passenger cars.

[torqhead]

Thanks for all the input, still working my way through this issue. I'm comfortable it's not a belt slipping issue. As I shared on my last updated, the amount the 94 amp alternator charging had dropped off during my first and second test which were monitoring voltage only. Ordered a DC clamp amp tester a few days ago and put it to use today.

Without fans and choke not running initially voltage read a 13.3 but dropped to 13.15 as it warmed up, added fans and it dropped to 12.8. Assuming the previous testing additional damage was done to the alternator as it was pretty hot when it got shut down (the 190+degrees) and hence why it started out lower. Added A/C while it was running and that finished the job as it dropped to 12.1.

There are 3 points I was using to collect amperage draw, although I struggled to begin with as I didn't realize I had the meter set wrong.. UGH Anyhow, by the time I got it set right I had to use my charger/booster on the car running at 50 Amps to supply power since the alternator took a turn for the worse. Net is, I'm not confident in my readings.

But I'll post what I have now and going to go through the process of getting charging fixed for another round of testing.

"A" = Positive of battery to starter
"B" = Positive of battery to alternator battery connection (10 gauge wire)
"C" = Alternator batter connection to fuse block and blower motor high speed relay

A B C Total
Ignition Off 0.2 0 0 0.2
Ignition On No Fans, Choke, A/C, Stereo 1.5 3.3 3 7.8
No Fans, A/C, Stereo 1.7 4.1 3.8 9.6
No A/C, Stereo 12.1 18.6 17.8 48.5
A/C on low Fan, No Stereo 8 13 28 49
A/C on high Fan, No Stereo 13 8 33 54

About the time I turned the A/C on with low fan is when the alternator took a dive and I turned on my charger/booster to finish getting readings.

[torqhead]

Originally Posted by torqhead

Thanks for all the input, still working my way through this issue. I'm comfortable it's not a belt slipping issue. As I shared on my last updated, the amount the 94 amp alternator charging had dropped off during my first and second test which were monitoring voltage only. Ordered a DC clamp amp tester a few days ago and put it to use today.

Without fans and choke not running initially voltage read a 13.3 but dropped to 13.15 as it warmed up, added fans and it dropped to 12.8. Assuming the previous testing additional damage was done to the alternator as it was pretty hot when it got shut down (the 190+degrees) and hence why it started out lower. Added A/C while it was running and that finished the job as it dropped to 12.1.

There are 3 points I was using to collect amperage draw, although I struggled to begin with as I didn't realize I had the meter set wrong.. UGH Anyhow, by the time I got it set right I had to use my charger/booster on the car running at 50 Amps to supply power since the alternator took a turn for the worse. Net is, I'm not confident in my readings.

But I'll post what I have now and going to go through the process of getting charging fixed for another round of testing.

"A" = Positive of battery to starter
"B" = Positive of battery to alternator battery connection (10 gauge wire)
"C" = Alternator batter connection to fuse block and blower motor high speed relay

A B C Total
Ignition Off 0.2 0 0 0.2
Ignition On No Fans, Choke, A/C, Stereo 1.5 3.3 3 7.8
No Fans, A/C, Stereo 1.7 4.1 3.8 9.6
No A/C, Stereo 12.1 18.6 17.8 48.5
A/C on low Fan, No Stereo 8 13 28 49
A/C on high Fan, No Stereo 13 8 33 54

About the time I turned the A/C on with low fan is when the alternator took a dive and I turned on my charger/booster to finish getting readings.

When I edit this text the table shows up fine.. Not sure what to do, anyone can tell me how I can post a pic of the table within the post?