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1963 Etype Coupe

1963 Etype FHC – Generator and Voltage Regulator Repair

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After my First Start and First Drive, I noticed that the warning light on the dash indicating a charging circuit fault was illuminated. This kicked off a longish repair cycle where I was able to deal with various issues and get the generator and voltage regulator systems in good running order. Following is one of my deep dives into this subject.

There is a lot of ground to cover here. Although the generator and voltage regulator system is simple by modern standards, I still had a learning curve to obtaining enough knowledge to fix my problems. My search for knowledge started with this thread on Jag-Lovers.

https://forums.jag-lovers.com/t/advice-needed-regarding-c42-generator-and-rb340-voltage-regulator/452247

In particular, thanks to Mike Eck, Tom Draude, and David Langley for their help. If you really want to take a deep dive, I would recommend the following link, which will take you to a full course of study on the subject. This document is 275 pages long and I certainly didn’t read all of it. But the sections that I did read gave an excellent, relatively easy to understand discussion as to how these systems work. It is worth looking into.

https://mgaguru.com/mgtech/books/lts_otcc.htm

In a more direct approach, there is the document “Lucas Generator and Control Box Tests” found at the following link:

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

This document gives step by step guidance to use in troubleshooting both your generator and your voltage regulator. My generator seemed to be working, in that I could register voltage output that made rough sense. The voltage regulator (VR) on the other hand seemed to be totally dead. Because I went through a lot of deadends, I’m going to skip to the repair process that did work.

The generator “field” resistance was showing too low of a resistance. I was getting about 1.5 ohms and I should have been getting about 5 ohms. In the pictures below, I have disassembled the generator. It turned out that the “field winding” was shorted locally to the heavy curved rectangular metal piece that the field wires were wrapped around. There are two of these and internally, they become electro-magnets. I “re-taped” the loop of wires that was shorted and this worked. While I was in there, I decided to replace the bearings at both ends of the armature shaft. One is a standard ball bearing, currently available from McMaster. The other bearing is an “oilite bushing”. I obtained a new old stock bushing from a source on Ebay. I am pretty sure the bad bearings were allowing the armature to scrape the field wiring and caused the local short. I did not replace the brushes as they looked to be in good condition.

I had an original RB340 VR in my box of parts. After much diagnostic work, I determined that I could not salvage it. The contact points were in bad shape. I could never get it to regulate the voltage correctly, much less the current. I wound up buying a new aftermarket VR from NAPA/Echlin. It is stamped Made in America. It has a similar shape factor as the original Lucas device. The terminal connections are exactly the same. I hooked it up and after running the tests from the Lucas Generator and Control Box Tests document, it seemed to be operating correctly.

The 3 screw pattern to connect the Echlin VR to the mounting bracket are the same. The mounting holes for the waterproof cover are not the same. To make it look original, I was able to mount the original RB-340 cover but this required drilling and tapping some new holes. Once installed, it would take a sharp eye to spot it versus the original.

You might ask why I am messing with a generator and its associated VR. The main reason is for purposes of originality. SNG and others sell various versions of a more modern alternator that is concealed in a housing that is a drop in replacement for the generator. SNG even sells a “mock” RB340 housing. That said, the wiring for an alternator is simpler and is an obvious “tell” for this type of installation. Except for JCNA Champion class concours competition, the alternator product is probably the way to go, from a reliability and electrical performance standpoint.

Below are some pictures showing various aspects of this work.

CW from the top: Partial view of end housing with brushes, generator case, fan, attachment hardware for fan and pulley, armature.
Original VR, original VR cover, generator end plate with brushes
At the bottom is the end plate that holds the ball bearing. My ball bearing was held in with the simple snap ring shown and was pretty easy to remove and replace. There were numbers on the old bearing that still make sense today, allowing me to order a new bearing from McMaster. The two long bolts go from end cap to end cap and are basically all that holding the generator together.
Here is a closeup of the armature and the commutator strips. I cleaned the commutator strips up with some fine sandpaper. I also cleaned up the shaft, where it inserts into the oilite bushing.
Old and new bearing. No differences. Mine was McMaster P/N 2349K221. The old bearing was definately “wobbly” and was probably allowing the armature to hit the field windings. I did not take a picture of the oilite bushing but I found it on Ebay, Item number 303853917799. Checking Ebay now, that source has dried up. You may find it as Jaguar P/N 2754 or Lucas P/N 189237.
Here are the field windings, removed from the generator case. They are held in with a single large cross head screw times two (see tapped hole at yellow tape) that you remove from the outside. Release the small screw that holds the electrical connection terminal and this bundle slides right out (obviously after you remove the end plates, armature, etc.) The wire bundle, which is wrapped in black electrical tape, will separate from the heavy metal plates, as there is no direct connection. I found small amounts of metal dust in the housing, which led me to believe something was hitting.
A view of the field winding, separted from the metal yoke.
Just for the record, this is the original RB340 VR. The round eccentric circles at the top can be rotated to change the closing pressure for the points. That said, I never could get mine to work to a point where this was important.
New Echlin VR in the foreground. It is similar in concept to the original, i.e. it is not some modern solid state device. An interesting technical note. The contact points are supposed to open and close at around 50 cycles per second. On my old VR, when they operated at all, they moved about 2 cps and there was arcing at the points. With the new one, I can believe that it is moving at 50 cps and there is no arcing.
The box.
As I said, it looks original.
Here is the generator.

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