Voltage Regulator

Page 17 of Volvo Technical Publication 31465/1 says "a hybrid-film voltage regulator, designated "TWC" is available as an accessory." Does anyone know anything about this?

Also, is the regulator with the plug for the battery temperature sensor still available? I know there were a lot of issues with it back in the day but I think it would be pretty neat to get it working now that batteries are sealed up so much better.

I don't have a copy of the greenbook you're referencing, but I'll guess that it's from the late 70s / early 80s, and is talking about an early Electronic Voltage Regulator for the Alternator (or Generator?), instead of the older Electro-mechanical Voltage Regulators.

The old regulators had one, or more, buzzing/switching relays to regulate the charging voltage to the battery. IIRC, some of them had a thermistor circuit to adjust for the temperature and provide better charging. The modern electronic regulators have built-in temperature compensation to provide consistent charging.

bobxyz said:

I don't have a copy of the greenbook you're referencing, but I'll guess that it's from the late 70s / early 80s, and is talking about an early Electronic Voltage Regulator for the Alternator (or Generator?), instead of the older Electro-mechanical Voltage Regulators.

The old regulators had one, or more, buzzing/switching relays to regulate the charging voltage to the battery. IIRC, some of them had a thermistor circuit to adjust for the temperature and provide better charging. The modern electronic regulators have built-in temperature compensation to provide consistent charging.

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That is definitely a possibility as the book covers 1975 onwards, however the pictures and descriptions make me think not. Specifically where they say that the newer regulator is labeled TWC and then show the TWC reulator as having a rectangular housing.
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Interesting about TWC. http://www.sagdahl.se/eng/twc_eng.htm

I've never seen one on a Volvo... or anywhere else.

cleanflametrap said:

Interesting about TWC. http://www.sagdahl.se/eng/twc_eng.htm

I've never seen one on a Volvo... or anywhere else.

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Awesome link!
#2 is almost definitely the one from the green book. Clarion makes stereo systems, maybe I'll email them and see if they have any information for me...

If any car ever needed remote temperature sensing at the battery, it was the Volvo 240, with its alternator under the exhaust manifold. On the other hand, in 20 years of owning them, I'm happy for the bias toward undercharging, having dealt with the alternative in other makes. I agree the remote thermistor wiring might have its own troublesome connector issues. The early 240s did have external regulators, and I've often posted this Volvo tip just to show the temp comp curve:

cleanflametrap said:

If any car ever needed remote temperature sensing at the battery, it was the Volvo 240, with its alternator under the exhaust manifold. On the other hand, in 20 years of owning them, I'm happy for the bias toward undercharging, having dealt with the alternative in other makes. I agree the remote thermistor wiring might have its own troublesome connector issues. The early 240s did have external regulators, and I've often posted this Volvo tip just to show the temp comp curve.

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That would make sense as to why they offered the TWC reg. Likely it was meant to take place of the short-lived external-sensor regulator from 85/86. I guess that means it's pretty pointless to pursue for my 740 Turbo with the alternator as far from the exhaust+turbo as possible.

I contacted Robert Sagdahl of RS-Elektronik (one of the original creators of the TWC voltage regulator) and got the following explanation:

The TWC-regulator were developed during the 1980 for enhancing the charging in boats.

Jaguar, BMW, Volvo and Saab had problems with their charging so they tried to put in the TWC and then the problems were solved.

In the beginning the TWC had a measuring phase that tried to see how the battery was charged, but that was taken out later. Though the charging has been proven to be very much better than the original regulators.

The production stopped in the early nineties, but a lot of regulator is still in use all over the world. The construction seem to be pretty good when it works after 25 – 30 years.

The company Truck-tronics in USA, https://truck-tronics.com/ has started to sell a unit that is working in the same way as the TWC. It has exactly the same charging profile as the TWC used.

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So, unfortunately, unless you can come across a used TWC you're out of luck unless you want to wire in a more modern take on the same concept yourself.
I don't like to modifying things unless the original design isn't up to my demands so for now it looks like my voltage regulator is staying where it is.

People used to wire in a ford regulator instead of the bosch ones. That also had better charging. Try the truck tronics place. Usually to wire an external regulator in to the alternator. All you need is the old styel brush holder with the three wire connections on it.

That's fun! Thanks for the info from RS-Elektronik.

The TWC-regulator were developed during the 1980 for enhancing the charging in boats.

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I was puzzled by why someone would go to all the trouble of making a regulator with remote temperature sense, but then bury the thermistor in the wiring harness instead of affixing it to the battery case. For automotive use, it didn't make much sense. But for boat usage, it makes a lot of sense. Unlike automotive use, boat batteries may be heavily discharged (think trolling on the electric for hours), and the batteries are often in a different compartment than the gas engine&alternator. With this, remote temperature sense near the battery can help charge the battery quickly but without over charging issues.

I wonder if 240 charging problems contributed to moving the alternator from exhaust-side bottom to intake-side top in the 940s?

bobxyz said:

I was puzzled by why someone would go to all the trouble of making a regulator with remote temperature sense, but then bury the thermistor in the wiring harness instead of affixing it to the battery case. For automotive use, it didn't make much sense. But for boat usage, it makes a lot of sense. Unlike automotive use, boat batteries may be heavily discharged (think trolling on the electric for hours), and the batteries are often in a different compartment than the gas engine&alternator. With this, remote temperature sense near the battery can help charge the battery quickly but without over charging issues.

I wonder if 240 charging problems contributed to moving the alternator from exhaust-side bottom to intake-side top in the 940s?

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Volvo must have agreed with you as they did try putting the temp sensor directly under the battery (in 85/86 740s I think) but with the leaky batteries of the time that didn't go well.