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240 Largest (amp) Alternator without Modification

VolvoScout

Member
Joined
Jun 4, 2012
Location
Upstate, NY
What is the largest (Amp) alternator that can be used with a 1990 240 without any modifications, perform reliably without breaking belts or overheating and won't get in the way of the oil pressure sensor?

80A option:
https://www.fcpeuro.com/products/volvo-alternator-244-245-240-242-740-760-940-dl-745-al157x

100A option:
https://www.fcpeuro.com/products/volvo-alternator-100-amp-740-760-780-940-al155x

140A (I assume this won't fit without modification):
https://www.ebay.com/itm/140-Amp-Vo...2349624.m46890.l49286&mkrid=711-127632-2357-0

And there are a few 70A options on Rockauto...
 
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I suspect it would take marginal effort to swap in a 115A alternator from a 968. Probably just swap the internals into the old housing, maybe even only the front piece and the plastic chunk by the posts to stop the wiring from shorting to the case, but I have never actually tried it.
https://www.fcpeuro.com/products/porsche-alternator-928-944-968-al170x

What's the 140A alt you mentioned? Your link points to the 100A unit.
 
I just corrected the link to the 140A option. (Another member on TB is asking about that specific alternator in different post)

I suspect it would take marginal effort to swap in a 115A alternator from a 968. Probably just swap the internals into the old housing, maybe even only the front piece and the plastic chunk by the posts to stop the wiring from shorting to the case, but I have never actually tried it.
https://www.fcpeuro.com/products/porsche-alternator-928-944-968-al170x

What's the 140A alt you mentioned? Your link points to the 100A unit.
 
I actually just purchased the BNR 140 amp alt & I don’t believe it’ll need any modifications to fit. All the gauge sizes seem to be the same, as well as the shape & size seem to correlate with the space it’ll be in as well. Regardless, I’ll update you once it arrives.
 
An even better question might be...how much does a higher maximum output alternator solve the problem you're actually trying to fix?

You may be better off using a marginally higher max output alternator but with a suitably-tailored voltage regulator.

With a stock style 7/9 series 100A alternator and such a regulator, I can run H4s, wipers front and rear, and the radio, at idle, in a cold rain, and not wish for anything more.

Perhaps you have a different use case, such as charging a homebrew battery bank, while making the weekly 40 mile grocery run, for use in the yurt, in which case the higher output might be needed, I don't know.
 
I'm installing an auxiliary battery connected via an isolator and looking to install fog lights, driving lights, and hoping to get the AC back up and running.

Plus the old alternator is starting to "kick the bucket" according to the mechanic that did the inspection on the car.

I'm thinking that 100A should be adequate, but I would like to know what options are available before I pull the trigger on a new alternator.



An even better question might be...how much does a higher maximum output alternator solve the problem you're actually trying to fix?

You may be better off using a marginally higher max output alternator but with a suitably-tailored voltage regulator.

With a stock style 7/9 series 100A alternator and such a regulator, I can run H4s, wipers front and rear, and the radio, at idle, in a cold rain, and not wish for anything more.

Perhaps you have a different use case, such as charging a homebrew battery bank, while making the weekly 40 mile grocery run, for use in the yurt, in which case the higher output might be needed, I don't know.
 
Beware FCP alternator

80A option:
https://www.fcpeuro.com/products/volvo-alternator-244-245-240-242-740-760-940-dl-745-al157x

I just purchased this alternator.

Verdict so far: Very bad!

On the stock alternator, the top bushing, where the adjuster locking bolt goes, is 1" thick.

On the Bosch alternator supplied by FCP Euro, this bushing is 1-3/8" thick. This makes it very difficult to install, and results in the alternator tensioner touching the water pump pulley. Bad sound, no good.

Also, contrary to the picture, it does not come with the pulley. Not a huge deal, but the picture is misleading.

After a very aggravating installation, I had to remove it and re-install my previous alternator. Which has great output but a very bad noise, apparently from the bearings.
 
80A option:
https://www.fcpeuro.com/products/volvo-alternator-244-245-240-242-740-760-940-dl-745-al157x

I just purchased this alternator.

Verdict so far: Very bad!

On the stock alternator, the top bushing, where the adjuster locking bolt goes, is 1" thick.

On the Bosch alternator supplied by FCP Euro, this bushing is 1-3/8" thick. This makes it very difficult to install, and results in the alternator tensioner touching the water pump pulley. Bad sound, no good.

Also, contrary to the picture, it does not come with the pulley. Not a huge deal, but the picture is misleading.

After a very aggravating installation, I had to remove it and re-install my previous alternator. Which has great output but a very bad noise, apparently from the bearings.

I had the exact opposite experience. I purchased the alternator linked on 6/16/21 and it was the same thing as the 80a that the car had previously. (and I still have, just blown diodes from a bad ground :roll:)

Fit perfectly out of the box. A couple days later when it was confirmed to be reliable I replaced the pulley with a 54mm overdrive pulley for better output at idle.
 
100 Amp 1992-93 940 turbo Bosch alternator puts out 140 amps at 8000 alternator rpm. But this alternator my be too big to fit a 240 without moving it to the other side of engine.
 
Plus the old alternator is starting to "kick the bucket" according to the mechanic that did the inspection on the car.

I'm thinking that 100A should be adequate, but I would like to know what options are available before I pull the trigger on a new alternator.

Have you tried a new set of brushes yet in the bucket-kicking unit?
I mean, pursue upgrades by all means, but if you can improve function cheaply in the meanwhile for a 20 minute "investment"...
 
Denso or Bosch from the efan oe redblock volvos works well on the mechanical fan 240 to run the a/c pusher fan and couple other bits.
Short of replacing the wiring & belt drive system, even if you leave the mech fan if you want A/C, no real way to increase the amps beyond that anyway.

I honestly think, even with perfect rubber accessory bushings/better washers or bracket and OE Volvo/Roulands belts that really grip that are near brand new, that it's not *really* possible to get more than ~68A idlin (max I could get out of the denso idling...the bosch 100A you can get ~50A on the Volvo pullies idling) outta *at best* ~66% efficient alt (even with a relatively efficient full bridge rectifier...yea, right :lol:) at perfect belt tension that somehow magically adjusts tension for temp/humidity more than that ~1-2HP off those 2 V-belts wrapped such as they are without destroying the bearings in the engine/alt or waterpump or impacting fuel economy or belt life absurdly adversely, even if the clutch fan isn't fully locked & the water pump isn't spinning all that fast on the larger pulley or breaking the bracket with the heater valve open/normalish use.

I was spinning it on a socket on the 2hp drill press and measuring the draw on my kill-a-watt @ ~B21/B23 @ 900RPM idle and smaller pulley than the B230...even the denso drawing ~70A & torque required is drawing ~1.2-1.5KW on the drill press' motor! IDK how you plan to apply that with rubber-steel over ~30?% wrap on a lousy 2" v-belt pulley, even with 2 belts perfectly aligned on the hooptie volvo.
All you ME boys go ahead and impression the thing for surface area, temp and coefficient of friction and tell me I'm full of it...or test it with a belt rig I suppose?
See Dave Bartons debacle with his primary e-fan adventures & more powerful alt idling in TX?

The voltage reg lowers charging voltage and doesn’t have a cutoff for that for hot climate idling over hot pavement with the a/c on in the Deep South or scorching az desert, this might be a problem.

No issues here or ca. Maybe there’s an alternate voltage reg for the 240 that puts the temp sensor on the inner fender apron that reads a temp something close to battery temp like the old external regulators did (tho for early 240 they were often flickery and way risky to under and overcharge as were the sketchy aftermarket adjustable regulators no thanks) or a way to duct some air that isn't coming off 130? blacktop, the exhaust manifold and the 160? propeller wash of the engine fan?

With the Bosch I suspect even under the exhaust for sampling air for the temp sensor, there’s a max temp resistance in the regulator temp sensor circuit above which they probably figure there’s no point reducing charging voltage as presumably all the liquid has evaporated/boiled out of the battery!

The later FWD cars (& plenty of others with internal regulator & temp sensor) have a cute little plastic duct to the temp sensor to much the same position on the fender on the back of the alt and heat sink on the rectifier to source air from ~where the battery actually sits.

I don’t believe the denso to be sub standard part in hot weather in construction as such or will cease to charge and it puts out more amps idling on the alt load tester, even if the Volts are lower in hot climates due I suspect it it sampling hotter air without a charging voltage cutoff minimum that the Bosch seems to have. Fewer amps from the Bosch idling on the alt dyno and larger to use on the 240T..if that matters.

I might have one more denso 100A. IDK on the Bosch...those are effective too!

Battery life in extreme hi-desert with super cold nights/early morning use and extremely low humidity and hot afternoons is brutal, even if the alt charges exactly according to conditions & it's a 240 with the battery away from the exhaust and with tons of air around it shielded from the blacktop. Super low charging voltage when you drive the car home in the heat, super cold mornings/thick oil and deep battery draw down & brutal shock/overcharging on startup...runs low on water and a nice lovely paste to short them out between the plates.
Coastal/no salt air highway driven 55 degree ambient temp 60% humidity or damper? Battery lasts forever!
 
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Denso or Bosch from the efan oe redblock volvos works well on the mechanical fan 240 to run the a/c pusher fan and couple other bits.
Short of replacing the wiring?

....

Agreed the belts are a limit and that wiring has to be upgraded.

I have been switching to Gates Quad Power 4 belts for my metalworking machines with great succes. They seem to hold up better than the other brands I tried. They look and feel to be much higher quality than some of the fast wearing automotive belts I have used.

Might be something to try? They are not cheap though. Bet there are suitable sizes available.

https://www.gates.com/us/en/power-transmission/v-belts/bandless-v-belt.p.9683-000000-000000.html
 
So without modifying belts and wiring, would my maximum amperage be about 100A or 80A?

Currently looking at either the 80A or 100A Denso.
 
The 100A can put out just below ~70A @ idling RPM.
If you plan to have some load in heat with the A/C on you might want that.
IDK what other uses you might have planned, however.

The 80A a bit lower, but it'll be more efficient at lower load & can charge the battery a bit slower/minimum output will be lower for (in theory) slightly longer battery life in some climates & less belt drag in the cold &/or if you don't run A/C, but ~50A max while idling.

I'd guess 70A is about the absolute limit of belt traction while idling +-, even if everything's in good shape from some primitive calculation, but I'm no experienced ME.

In NY the hot weather concerns of idling over hot pavement of the Denso temp sensor (there's probably a remote temp sensor option for it if someone really dug deep) is probably no big deal.

IDK how much time you spend at idle, & the car can run off the battery for short periods of course...
...If the A/C works I'd want the ~70A available at idle for the pusher fan, but what do I know?
 
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