Classic cars forum & vehicle restoration.

[Bitumen Boy]

Hi all, been having some odd symptoms for a while now with my temperature gauge readings being all over the place, after a bit of tinkering and parts swapping I suspect the voltage stabiliser - a repro, iirc. It's not down to the engine, as it couldn't go from stone cold to boiling and back again in under a minute, or give some of the high steady readings I've had without making an impressive amount of steam... Looking around online there are a few solid state replacements available, so I was wondering if anyone had any experiences with them, good or bad? All thoughts welcome as ever

[ukdave2002]

Just nip in to your local electronics shop and get an LM7810 it's a simple 3 pin fixed voltage regulator, will cost about 45p. It's in a TO-220 case, so can be easily hidden, it will regulate to 10v same as the "automotive" ones, google it for the pin connections.

Cheers

Dave

[Bitumen Boy]

Thanks for that, Dave - I'll have a crack at it, the price is rather more attractive than I've seen previously and I don't mind a little soldering. Reading the datasheet they're good for up to 30-odd volts input so I'm assuming that should be OK with a dynamo charging system?

Will have to be mail order again though - nearest shop to me for this sort of stuff is Maplins in Cardiff, ~30 miles away...

[Bitumen Boy]

Time for an update on this. I got one of the devices Dave mentioned, and fitted it by soldering some short flying leads to the pins, insulating with heatshrink sleeving, and using standard crimps as appropriate to connect to the circuit and provide a good earth. It didn't take much longer to do than to write about it, and cost a lot less that the ones on fleabay which are essentially the same thing. Checking with a multimeter shows it giving a nice steady 10v with the engine running and dynamo charging, so all good there, thanks to Dave.

Of course I decided to pry the old one open and have a look at it, and I got a surprise - that was a solid state device too, packaged in an old style casing. This may have been contributing to the odd symptoms I've been having with it, as earthing relies on the circuit board making a good connection with the metal casing where the two are crimped together. Obviously earthing is important for these devices to work properly, and that strikes me as being a rather poor design.

Is my temp gauge working? No chance! A new sender causes it to read high while the old one appears to have failed with an intermittent open circuit. Earthing the terminal that connects with the sender causes the gauge to read maximum, so I'm assuming that's OK - though if anyone has any test data to check it out with I'll have a look. I've now ordered another sender from a local factor - it's the same as a Mini one, so still listed - on the basis that if it turns out to be junk I can take it back easily. The other new one I had was so cheap as to be not worth sending back, time the postage is taken into account - it was via Ebay and past experience is that they're only interested in making the seller refund the item cost, you can whistle for the return postage.

[ka]

Sorry, confused at this one, is the vehicle 6v or 12v?, if 6v, charging at 10v sounds high, if 12v, then 10v is low.
Are the senders you are obtaining 12v? the mini one will be if not the others.

I am aware that a classic alternator charges at around 14v, do 6v vehicles normally charge at 10v?
_________________
KA

Better three than four.

[ukdave2002]

[ka]

Thanks, I understand more now.
Glad I chose the capillary tube type.
_________________
KA

Better three than four.

[Bitumen Boy]

[Bitumen Boy]

Collected the second new sender from the factors last week, but no time to fit until today. I now have a working temp gauge though I wasn't sure at first - thought it was under reading, but testing back at base with a glass thermometer, improvised rad muff and brick on the throttle shows it to be pretty accurate, it's just that the engine is running a little cooler than I would like. IIRC it has a summer thermostat in because it seemed to be running a little too warm a couple of years ago, maybe that was the gauge reading high due to an ailing sender or stabiliser.

I've also had a read up on zener diodes, but if Dave reads this I'd still appreciate some input to make sure I don't go and let the smoke out of the wires...

[ukdave2002]