Bosch universal 90A alternator possibility
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    1. #1

      Bosch universal 90A alternator possibility

      I want to upgrade the 33A Motorola alternator in my 1969 122S to a high current Bosch unit. I see that I can get a re-manufactured 55A Bosch one that apparently came standard on 140s and should probably fit my B20 quite easily, is it really that simple? Even if those fit though, they are slightly expensive (and hard to find) and I can get a brand new so-called "universal" 90A one for cheaper. I am looking at something like https://www.olx.co.za/ad/bosch-unive...-ID15QwmM.html and would like to know what type of work/fabrication would be needed to make it fit. Is it even possible?

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    3. #2
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      For what it's worth, I've installed the Bosch 55A alternators on both B20 and B18 motors. I had a bracket to adapt the alt mounting to the B18 that doesn't have the cast tab for this purpose. Some (late) B18 motors already had this cast tab, but as you have a B20, not an issue. I had the external regulators that accompanied these alts and did the minimal wiring necessary. There is an electronic regulator for the 55A alt available that Planetman recommends and sells, but I didn't go that route.

      As you're in South Africa, probably not a lot of these cars around to source an alt from. Late 1800 also came with the 55A alt.

    4. #3
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      Installing a larger alternator is not a huge technical undertaking. As noted by Daniel, installation of the later 55 A Bosch alternator is probably the easiest size increase path allowing you to retain the external voltage regulator (depending on the field resistances, the existing Bosch 35 A regulator may not be optimal for the 55 A regulator; but, would probably work).

      If the cost of rebuilt 55 A Bosch units is excessive, there are lots of options. The biggest issues with non original alternators are the mounting tab/ pulley offsets and the direction of rotation. I have seen the installation of alternators using some pretty cobbled up spacers to get the pulleys into alignment. Some of the mounting methods result in a lot of side thrust on the mounts with the result that I expect that they don't stay in alignment for very long with unhappy results. Alternators are alternating current devices, so the direction of rotation of the field winding is not important; however, the cooling fans are definitely directional in terms of air flow and changing the direction of rotation on an externally mounted fan will render it pretty ineffective with a commensurate reduction in life for your alternator. I suggest you do a search on Swedespeed. There are a number of threads that have addressed the installation of larger / non OEM alternators on the B20. There are various Delco units that seem to be popular.

      Some later alternators offer the 'one wire' option. This eliminates the external voltage regulator and also eliminates the charge indicator light function. You can get later model internally regulated alternators that retain the charge indicator / field flashing function if you want the charge indicator. Be aware that problems with the charge indicator light circuit are a common cause of failure to charge problems on older alternator installations. Alternator installations with a charge indicator light typically use the trickle current through the indicator light filament to flash the alternator field so that the alternator can start to generate an internal voltage. If the filament burns out or there is a bad connection in that circuit, the alternator fails to flash resulting in non operation. The one wire alternators have an internal flashing circuit eliminating that failure point.

      As an observation, unless you have air conditioning, are running a lot of auxiliary lighting or a huge load of Class D subwoofer amps, the original 35A alternator should be just fine. I have a 1971 142 with the Bosch 35A alternator. I replaced the Bosch external voltage regulator with the adjustable regulator sold by DaveBarton.com. With the setting on the regulator, my 900 RPM idle voltage is typically around 13.4 volts. Turning the headlights and the interior fan on will cause the voltage to drop to 13 volts or less; but, I have never seen it go below 12.5 volts at idle. Above 1500 RPM its pretty steady around 13.2 - 13.4 volts. I don't have any problem keeping my battery fully charged. I think the biggest impediment to reliable operation of the electrics on vintage Volvos is the condition of the wiring and electrical connections. If your wiring is compromised, a larger alternator is not necessarily going to improve things.

      Edit:

      I was looking at the link to that universal Bosch replacement. I think the single largest challenge would be the lower mounting point. That mounting point is nothing like the mounting point on the original Bosch 35 A or 55 A alternators, or even similar to the Delco Si alternators. It sort of reminds me of the mounting arrangement on my old B230 FT.
      Last edited by 142 Guy; 03-21-2017 at 05:56 PM.

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    6. #4
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      How much do you really need? I'm still running the stock generator on my 66 with no problems, including winter driving with the heater, lights and radio on all the time.
      However adding things like extra lights or an electric cooling fan might be different story. Or a huge sound system those can draw alot of current.

    7. #5
      Member LloydDobler's Avatar
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      The real question is if you can buy Chevrolet/Delco alternators down there. If so the far simplest and lowest cost conversion is the bracket kit from swedish embassy. Then you just buy your own alternator and wire it in.

      http://www.sw-em.com/altkit.htm
      2003 C70 T5M Convertible - Eibachs, Koni FSDs, Enkei RSF5s, OBX downpipe, Snabb intake, RIP kit, & drop-in intercooler, Quaife LSD, 19T, Green Giants, 22 psi Hilton tune.
      2001 V70 T5M - Black on black, H&R springs, Triton wheels, Koni FSDs, Daily driver
      1966 122s - Collectible project, restoration and many mods on the way.
      RIP - 2004 C70 HPT Convertible, 5 speed swap

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