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MG TD TF 1500 - Need Generator/voltage regulator second opinion

Now that I have the TD engine running, I'm on to new "challenges" with the car. It seems I'm having trouble with the charging system. It started with the ignition warning light not working. It turns out it the bulb was too large. I replaced it with the correct 2.2watt bulb. The good news is, it works - the bad news is, it never goes out.

This led me to test the generator. I disconnected both terminals and wired them together. I connected my voltmeter to the terminals and to ground. With the engine running, the voltage jumps at around 1100 RPMs. So it looks like the generator is charging.


So next I followed the regulator testing procedure in the workshop manual. I disconnected terminals A and A1 and connected the wires together. I connected my voltmeter to terminal D and ground. With the engine running I get 2.5 volts at any RPM. According to the manual I should see 15.8-16.4 volts. I followed the procedure for adjusting the voltage and it would not change.

I assume the regulator is shot. It looks like such a simple device. Has anyone else had these symptoms and found a cure? Should I just order a new regulator?

Thanks!
Evan
Evan Ford - TD 27621

Evan - "I disconnected both terminals and wired them together. I connected my voltmeter to the terminals and to ground. With the engine running, the voltage jumps at around 1100 RPMs". What was the voltage that you were reading at this point? You should see the voltage continually increase as the revs go up and want to hold it to no more than 20 volts by keeping the revs low (around 1000rpm). If you don't see this, then the generator is bad. I don't know what you mean by seeing the "voltage jump". The only time you should see a discrete jump in the voltage is when it the generator and regulator are hooked together. Cheers - Dave
David DuBois

Evan ---- Dave has already asked the question I was going to ask. So repeat the test and give us the answer. The 2.5 volts sounds like what you get from residual magnetism. Or in other words the field is open. You could easily check with an ohmmeter (to ground). Let us know what you find!
Regards,
Bob
R. K. Jeffers

Sorry, I meant to say the voltage rose rapidly at about 1000 RPMs. The voltage rises so quickly I described it as a jump. The analog meter I have only goes to 16 volts. The needle swept across to the peg and I backed off the thottle.

Bob, I'm thinking the regulator isn't ever charging the field coil. It's like the genny is sitting at residual level, like you said.

I'm still thinking it's the Voltage regulator.

Any ideas?

Thanks!
Evan
Evan Ford - TD 27621

Certainly the gen is working, so it is wiring or reg. Contacts oxidise whilst sitting, whether new or used. Did you try cleaning the contacts in the reg? Manual does a good job telling you how to set up everything inside, but unless points are badly burned simply clean should fix it. Given quality of parts today, make every effort to save the original. They are pretty bulletproof.
Given what you have done so far should be no problem - congrats! (can drive a long way on a good battery in the daytime!!!)
FRM
FR Millmore

Evan - I agree with Bob and Fletcher. Just one addition to Fletchers addvice to cleand the contacts int he regulator - disconnect the battery ground first to avoid a fireworks show in the regulator if a wrench or screwdriver gets where it shouldn't by accident. This is probably preaching to the chior, but reminders never hurt. Cheers - Dave
David DuBois

Thanks guys!

I'll try cleaning the contacts to see if anything changes. Hopefully I will get lucky.
Evan Ford - TD 27621

To Evan ----- Just remember that the description of the mechanical adjustments in the workshop manuel is for the 9 post regulator. The 5 post mechanical adjustments are different. Look in an MGA shopmanuel. Dave and the others are right, often the contacts become corroded and do not make contact. Have had contact with owners that have purchased NOS regulators that did not work, and that was the problem. Best solution is to go to a solid state regulator, no problem with corroded contacts.
Regards,
Bob
R. K. Jeffers

Bob - Where can one obtain one of the solid state regulators? I may be having a problem with the one in our TD (haven't investigated it yet) and I sure wouldn't mind going solid state, particularly if it can be mounted in the original housing. Thanks - Dave
David DuBois

Thanks guys!

Bob,

Not another manual! I guess I would have to buy a MGA to go with the book too... Don't tell my wife. She's already worried that I'll look for another project now that the TD is nearly complete.

I did some searching and found the Lucas test manual for voltage regulators in the December 1990 TSO. The CDrom comes to the rescue again. The same testing outline is available on this website http://vintagemg.com/ArticlePDFs/Tech103.pdf
Thanks to the Vintage MG Club of Southern California! I also found an article in a different TSO that listed the internal values for each circuit in the VR, so you can test the components with an Ohm meter.

Hopefully I'll get a chance to test it later today.

Dave,

I came across this link while I was searching above. It has the description and part number for a solid state Bosch VR. http://mgaguru.com/mgtech/electric/ssvreg.htm It might be worth a look if it will fit inside the bakelite case. I quick google shows it's about a $30 dollar item. http://www.donscofuncar.com/elecIgnition.html

Regards,
Evan
Evan Ford - TD 27621

Evan ----- Good luck with your testing of the regulator. If you try that Bosch type let me know the results. It is certainly cheap enough, but it does not appear to have an adjustment for output voltage. Also I doubt it controls the current output which could allow you to burn out the Lucas generators in our LBC's. Early TD's had a rating of only 17 Amps.
Best of Luck, Bob
R. K. Jeffers

Well, it's finally charging! It turns out I had two problems working at the same time. You guys nailed the first one, the regulator contact points were a mess. I took the regulator off of the car, cleaned the points and tested each circuit with an ohm meter. All of the values were withing factory specs. After putting it back on the car, the warning light would flicker on and off, then stay on. Since I knew the regulator tested good, I disassembled the generator. I found one of the brushes was hanging up in it's carrier. It was only touching the commutator on one corner. I filed the carriers to allow the brushes free movement, and lightly cleaned the commutator with emery cloth. Once I put the genny back on, the charging system worked like new. I did have to adjust the the regulator to bring it back to factory specs.

On the bright side, I know the charging system inside and out after this!

Thanks again for the help.
Evan
Evan Ford - TD 27621

This thread was discussed between 07/05/2005 and 09/05/2005

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