1974 Bluesmobile Gran Fury with a LOT of added stuff for parades etc. With AC, lights, etc on we get red light at volt gauge and yellow caution on Sniper at idle and slow cruise. I have police 85 amp alternators I could send to Plum Crazy for rebuild BUT see the Tuff Stuff 130 amp for an option. Anyone use that unit? Will it fry the stock 400 chassis wiring harness? Any help appreciated. Jake

You need more amps at low speed which isn't necessarily the same as big amps at high speed. You need to dig one layer deeper and look at the amp curves for the alternators. Start by figuring out how many amps you need at idle. Turn everything on with the engine at idle and measure the amps being used. You might be able to solve the problem by turning the alternator faster with a pulley change. If you need a new alternator then shop for one that provides the amps you need at the RPM the alternator is turning at idle.

Good advice.
But do verify the wiring is not contributing to the issue due to undersized wiring, poor connections etc.

Exactly. Some of the low amp alternators actually put out the most amps at low RPM. Spinning it faster with different pulley(s) is a sure way to improve the situation.

Andy, thanks for the help with the Sniper project on this same car. Runs good but Comp roller hyd lifters are junk. Great Race canceled for 2020 but the spending continues. We have 1. House battery in trunk. 2. 110v Smoke machine so we can throw a rod. 3. Yamaha 110v PAS DJ system. 4. 110v invertor. 5. Police lights. 6. Spotlight. 7. Dual Police PA system. 8. RV transfer switch etc and I am sure there is more. Fire Hazard for sure. Phish

You can buy a clamp ammeter for $50 at Home Depot and then you'll know what your amp load is at idle with everything running. Once you know that number you can look at amp charts for various alternators and find one that works for you.

Your car needs is sucking the same load coming from alt than coming from alt+batt combined. This stage would show a discharge reading on ammeter. So, having a 130 amps or 500 amps alt your car will suck the same. You would need to make just a propper mantenience on wiring/conectors and reinforce the wiring on the side required. I meant. Depending on where you are sourcing all the added stuff that's the point to reinforce.

You are talking about voltimeter reading, but without mention what of the stock wiring or even if you still are using the ammeter on car to make some wiring suggestions.

The deal is keep the batt out of the game the most as posible.

Alternator doesn't burn wiring by itself. Alternator just provides what the car needs, but if wiring is not propperly matched TO THE CAR REQUIREMENTS, SETUP or in good conditions that would be the problem. Amperage is not pushed in, but sucked by the car.

As mentioned, increasing the alt speed with a smaller pulley will help on the iddle stage for more amperage sourcing ( which is the biggest issue old Mopars got ), but, if you are using a later "85 amps" unit, mostly sure you already have the small pulley on it. Hard to say without pics of the alt you have.

Many smaller 80/90s 'denso'-style junkyard alternators provide enough charge at idle.

I have a Tuff Stuff 130 amp alternator. It works as advertised.

It doesn't put out as much current at slow speeds as modern alternators, but once you get past idle, it really begins to rock & roll.

If you have factory A/C and don't want to re-do all your pulleys and brackets, be aware that in factory A/C applications with dual belts that turn the compressor and the alternator, the alternator sits farther back on the engine compared to non-A/C cars that use a single belt for the alternator. The back of the alternator is in very close proximity to the passenger side cylinder head in this case. Most other alternators (Denso, GM-based Powermaster 140-amp unit) are too large in the front-to-back dimension to fit there with correct pulley alignment due to cylinder head interference. As far as I know, the Tuff Stuff 130-amp unit is your highest output option without major changes to your belt drive. If you don't have factory A/C, your options open up quite a bit.

Google "SAE Automotive Wire Chart", and you'll find that you need to use #2 wire with this amperage. I don't remember if your car uses a full-current ammeter or a shunt-operated one, but this much current will fry a full-current ammeter, and likely the wiring. Your best bet would be to run a #2 SGX wire directly from the output stud of the alternator to the positive battery terminal. You might want to bypass the ammeter in the car by putting both wires under one stud.

actually the difference is not like that. True the alt bracket fits different, but more due the A/C compressor bracket which uses the provisions used on non AC cars alt bracket, so the alt bracket for A/C was fit deeper, and also fits behing the front ear of the alt ( diff than non AC where bracket fist in front of alt ), but alt itself remaints practically on same spot. This is so true than you still can use a dual groove pulley alt into a non AC car and belts will match...also backwards




true about the wire gauge for 130 amps if you were to use those 130 amps, but our cars won't ever require 130 amps, so the wiring must be matched more with the car requirement loads than the alt load capacity itself. Just the starter motor plays on 90-120 amps rate, hence the wire gauge used between batt post and starter motor, but not the rest of the car. But still with a 130 or 150 battery cranking power, you still feed the car with a 12 or 10 gauge wire into the cab. Same than at home you get a 2 or 0 gauge wire into your breaker box from the street but spread it around with 10, 12 or 14 gauge all around depending on the device to feed coming out from breakers, no matter the street load capacity

Shunted operated ammeter began on 75 ( 76 on A Bodies ). I can't tell if earlier on C bodies ?

No need to bypass ammeter if car and accesories are correctly wired and sourced. On ammeter cars NO ONE ACCESORY must be sourced from batt side of the ammeter, Everything must be sourced from alt side. Thhe Battery won't suck ever more than 40 amps if discharged. You can't push in the amperes, so the batt gets its own load recharge process due the chemicals speed.

Throw a wire between alt and batt post will make unusefull the ammeter ( if still present )

"actually the difference is not like that. True the alt bracket fits different, but more due the A/C compressor bracket which uses the provisions used on non AC cars alt bracket, so the alt bracket for A/C was fit deeper, and also fits behing the front ear of the alt ( diff than non AC where bracket fist in front of alt ), but alt itself remaints practically on same spot. This is so true than you still can use a dual groove pulley alt into a non AC car and belts will match...also backwards"



Perhaps in some cases, but certainly not all. I am talking big blocks here and failed to mention that.

On late 60's cars, into the 70's, cars with no PS and no AC used one belt and a one-groove crank pulley. That belt turned the alternator and and the water pump. Simple.

Add power steering to the mix and you got a 2-groove crank pulley with the power steering groove in front of the alternator groove. The spacing of the groove for the alternator was the same as the once-groove pulley, so the alternator brackets remained the same with or without power steering.

Add factory A/C and things changed. You got a 4-groove crank pulley with two grooves added behind closer to the engine. Power steering still used the front groove, the spacing remaining the same as the two-groove pulley mentioned above. The water pump spacing remained the same but often grew an idler pulley since the alternator no longer used this groove and there had to be some way to tighten the belt. The A/C and alternator used the rear grooves, which moved the alternator farther back. Even the Chrysler alternators with a protruding hump on the back will interfere with the cylinder head in this configuration, but not in the one belt and two belt configurations.

There may be other setups, but this is quite common. I have all three types of crank pulleys in my box-o'-crap that I'd be happy to post the photos of, if it will help anyone. Also the photos of the same type alternator installed in both configurations, and the relation of the back of the alternator to the passenger side cylinder head.

Thanks guys. I disconnected all the "house battery" 110 etc stuff and went back to basic C body car with 1 battery no cross over solenoid. Engine battery 12.4 with car off. Start and idle 13.5 on meter and 13.4 on Sniper. Lights and wipers at idle, no red warning light. Turn on AC with all that on and we drop to 11.4 on meter and flashing yellow 11.3 on Sniper, red light in dash. Car is factory AC and has a Wuhan (probably) Oreilly alternator on it. Will try the Tuff Stuff and report back. Phish

https://www.youtube.com/watch?v=3DhyEmEu2ks

Few years ago I installed a used Ford 3G alternator from a Thunderbird. Max. amp output a full rpm was about 95 I recall.
Engine idling at 500rpm, Interior fan ON, headlights ON
13.1v charge.

Somewhere last year the 3G alt got replaced with a used later model nippondenso alternator and the same idle charge was maintained.

No need to spend big bucks on 'brand' alternators that are no better than (modern-ish) stock factory stuff.

I run a Denso 60 amp alternator in my Duster and it holds close to 14v at idle. That is with the big Dominator EFI computer, 8 coils, 8 injectors, big fuel pump, etc. The modern OEM alternators put out a lot of amps at idle. I also make a bracket kit for the 90A Denso but it is a low mount which wouldn't work with a fuel pump.

I bolted a modified GM CS 144 alternator onto my car to eliminate the low amperage issue at idle. It's capable of putting out around 130 amps at idle and over 200 above a fast idle. They use them in Escalades etc. It bolted in the stock location with an inexpensive adapter bracket.(https://store.alternatorparts.com/a270-delco-chrysler-alternator-conversion-bracket.aspx) and I had to use a short sleeve and a longer bolt to move the adjusting arm into the correct position.

I did upgrade my underhood wiring to feed my accessories without going through the bulkhead plugs using a Mad Electric style set-up with a distribution block. No more low amperage problems, and no one even notices the change when the hood is opened. I rerouted my fan belts to accommodate the under alternator Sanden A/C pump and get better blt wrap than what the Bouchillion, Under Alternator Mount Kit provides if installed per the directions.