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Bosch RE-55 Regulator with Motorola Alternator

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Topic: Bosch RE-55 Regulator with Motorola Alternator
    Posted: Sep/18/2017 at 12:48am
As per the title, can I use a Bosch RE-55 regulator with the Motorola alternator assuming this is what I have.

The alternator, from a 71 Javelin, which has no identification on it at all:



My wiring nightmare for 74 Gremlin, you can see the RE-55 at the loser left of the picture, the car was running a 360 that came out of a 70 Ambassador, so had the earlier style alternator with the black plastic on the back of it:



Also, I'm presuming this is a relay for the ignition/starter, the car also has the round style starter relay?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2017 at 5:52pm
That is a 1971 and later alternator and you can't, or SHOULD NOT run a 1970 or earlier regulator with it.
The 70 and earlier regulator will regulate a volt too high as it expects the isolation diode of a 70 and earlier alternator to DROP the output by about a volt. So instead of, just for example, you getting 14.3 volts to the battery, the regulator would look to regulate at 15.3 - likely overcharging the battery. 

I don't know about a Bosch RE-55 without looking it up - and I can't see any regulator in the photos unless there's one of the brush-mount sort hanging on some of those wires.

If you attempt such a modification - and that's what it would be since that particular Motorola was never meant or intended to be handled like that, you'll likely have to modify wiring to fit your new scenario. 
Would the regulator handle the current draw of that alternator? Likely, but I don't have any such Bosch to check out the specs and what I look up is all over the map - I get multiple images, etc. so can't even tell for sure exactly how one is wired or what they look like. 

The Motorola is set up so the one brush is the ground side of the rotor winding and the regulator supplies the power only. 
It's also set up so that it gets field excitation power via the dash ALT bulb - and as a secondary source, the ign circuit in case that bulb burns out. 
How is the field excited with the Bosch unit?

(Chrysler, for example, powers the brushes and the regulator regulates by grounding the brushes - just an example to show that different systems have different field wiring setups)

By the way - a 1970 alternator would NOT have any black plastic on the back of it....... not sure what you refer to but MAYBE you mean the phenolic brush cover used on 69 and earlier.
If it was lacking the metal brush cover that has the ground tab, it was likely either modified or was a 69 or earlier.
1970 used the exact same metal brush cover as the later ones used, but the difference between 1970 vs. 71 and later is the fact that 71 and later don't use an isolation diode while the 70 and earlier ones did. 
But the brush cover was the same in 70 as 71 and later, meaning you can't tell the year by the brush cover. 
Now it's possible, even likely, that someone butchered the alternator, bastardized it like many rebuilders do and put the wrong parts on and called it whatever they needed to call it. 
I can't tell you how many rebuilt units I've gotten that had BOTH brush covers! The phenolic AND the metal cover over top of that. (rebuilders are  - well, they'd ban me here if I said what I really think of them)

(by the way  - the brush covers of 70 and later Motorola alternators are actually a zinc plated brass - that's why I didn't call them a steel cover  Wink   )

The answer on the Bosch - it would be a modification - and you'd need to figure out wiring. I don't have any decent info on that regulator. I'm not sure if it would fit or not, physically speaking. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2017 at 7:58pm
Thanks for the reply billd, I was hoping you might chime in.

The RE-55 is basically a solid state electronic regulator that replaces the older external regulators on a lot of Australian cars, it has 2 terminals, DF and D+ and gets power from the ignition (possibly via the dash light) to one of the terminals then both terminal run to the alternator. I don't think any of these charging systems run an external isolation diode.



You may be fight about the alternator with the phenolic cage as I think it is the same as on my 69 Javelin, I will have a look and see if it has any details on it. I have another one that came with the Gremlin and was running via the RE-55, so it may be that I just use this alternator rather than the Motorola one from the 71 Javelin otherwise I can probably use the correct matching regulator from the Javelin as well and rewire it to factory specs.

Just trying to come up with the best solution for something that has suffered years of wiring butchery by persons unknown.

Where you said "It's also set up so that it gets field excitation power via the dash ALT bulb - and as a secondary source, the ign circuit in case that bulb burns out". Does that mean that one of the two sources is essentially redundant and/or can I just bridge the two together and supply 12 volts from somewhere?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/19/2017 at 5:53am
Ok, bit of an update on the situation, this is the alternator that goes with the RE-55 regulator from the Gremlin harness:



It has Bosch Australia on the back of the housing and is the same as the one on my 69 Javelin, so might be part of the Australian content installed on the cars built here.

+12 volts from the ignition goes to the D+ terminal with D+ and DF terminals on the alternator connected to their counterpart on the regulator.

I suspect it would be advisable to just use the Bosch alternator. I think the only downside might be that I think they are only 35 amps or so but it makes for an easy upgrade to a one wire alternator later.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Sep/19/2017 at 11:09am
Below is the basic typical wiring for an AMC system with Motorola.

The way these work is that the initial current to start things charging comes from the ALT light, via orange wire or the ign system via yellow. You can get by without the yellow as long as the orange path and ALT bulb in the cluster is OK.
Once it starts spinning and charging, then current to supply the field comes through the REG sometimes labeled AUX terminal on the alternator. In other words, it supplies its own current for the field. 

I'm not sure how the power TO that Bosch regulator is supplied - but it would need to be switched. 
I could imagine that the DF may go to the field - that would make sense, and the D+ may come through the dash light. That could also work........... and if the D+ also went to the REG/AUX output, which on the later Motorola is the output of the field diode, or diode trio, it could control a dash light as well.
So if D+ went to a dash light AND to the aux/reg terminal and the DF went to the field - the brush, and the case was GROUNDED well, it may work fine. 
The black wire of the Motorola regulator is to ground the regulator to the alternator. They wanted BOTH to share a common ground so as to not have the alternator ground be good and the regulator ground be iffy and telling the regulator that the voltage was low because of voltage drop at a bad ground. So if they were grounded together, that issue wasn't possible (or was less likely.)
If the Bosch regulator was either attached to the alternator or had a ground from it going to the alternator, etc. then that accounts for the black wire. 

So the Motorola regulator has 4 wires - 
Green to field (brush terminal) and that MAY be the same as the Bosch DF
Black to alternator for ground - the Bosch would lack this but if it was WELL GROUNDED or attached to the alternator, that would account for that wire.
Yellow to ignition - a redundant source of field excitation.
Orange - from dash light and TO alternator REG/AUX for field excitation and light control - perhaps the D+ on the Bosch.

Hmmmmmmm....  if I got my hands on one of those I might have some fun and see about mounting it on the alternator and doing some testing.
The more I think about it, the more I think it might work. 
Looking at your Bosch alternator - it appears there are provisions for mounting the regulator right onto it - if that's the case, that accounts for the lack of a black ground wire - it's not needed.
I have a NOS Bosch alternator on the shelf in my shop. Dang it, now I have to go look at it again and see what the back side of it looks like. You got me curious. 

And I would bet that the Bosch was what was used there indeed. Bosch is good stuff. 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/19/2017 at 5:19pm
That makes sense, on my Javelin, there is a ground wire running from the alternator to the regulator case, which is mounted on the inner fender. It has an Ingram brand solid state regulator rather than the RE55 and looks more period correct but still has the same connections as the Bosch one. The Bosch RE55 came later and was commonly retrofitted into other cars to replace the old electro mechanical regulators since they were usually a lot more reliable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2017 at 5:50pm
Managed to get this sorted in the end.

I was just going to use the Bosch alternator with the RE-55, but after spending a hour or so cleaning it up, found that it doesn't fit into my nicely painted up US style alternator bracket, the mounting bolt holes are about 1/4" further apart. Aussie cars used a special alternator bracket that incorporated a remote mount for the oil filter since the steering box and oil filter need to fit into the same space.

Anyway, using the orange wire from the dash light to power the alternator and RE-55 as per the factory arrangement and the field connection from the RE-55 to the field terminal on the alternator, it appears to work. The connection to the ignition circuit is not required.

Thanks for your advice on the matter Billd.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Nov/10/2017 at 7:40pm
Correct - the yellow was added later as a redundant method to excite the field in case the dash light bulb was bad.
The early systems used three wires rather than four.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2017 at 7:30am
Any reason you really need more than 35A? That's plenty to run a stock car with AC. Modern radios don't use as much power as the old originals, unless you have a big amp in place. Just the head unit with built-in amp won't draw more than a stock radio. Unless you plan on installing things that take a lot of power I wouldn't worry about alternator output.
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