New Wiring Loom Problem

[gemmachine]

Hi I'm new here hope you might be able to help me.
I have just fitted a new loom to my 1959 Dexta as the wiring was in a mess although all was working before. I have fitted a new combined key light switch and heater button which was missing before. The battery has a positive earth as before and the voltage regulator has four terminals. I have followed the wiring diagrams very carefully and connected everything up. My problem is that when I switch the key on I have found that the F and D wires going to the dynamo were getting hot and shorting out in the Dynamo. On testing the voltage on these wires both are live with 12 volts and the dynamo works like a motor. Can anyone help with what might be wrong?

[Tubal Cain]

You should double check your wiring to confirm that it is correct.

It sounds as if it might be a problem in the control box, check that the cut out points are open and that they are not welded together.

Gerald

[PghBill]

Go to the Dexta Forum page. Click on Stefans Workshop Manual.
Scroll down to the 3rd RE: and click on this link- http://tractorspares.ie/Manual%20Part9.pdf- go to page 11.
Might help you figure it out
Bill

[gemmachine]

Thanks for your help and replies I haven't had a great deal of time to test out your ideas as I have the Dexta at a friends and with the dark nights it's not so easy to find the time to work on the tractor.
What I have found is that if I disconect the yellow/white conection at the base of the steering column from the warning light (which does't light even when power seems to be going through it) both the D and F conections no longer have power in them.
Can you tell me if the D and F wires should have power in them when the ignition is turned on?
I can't work out how the charging light works, as it seems to have power from the battery and also once the engine is running power from the dynamo but the when the engine is running the light should be out?

[Tubal Cain]

Assuming that your electrical system is working properly without any problems, when you switch on your ignition, current flows through the warning light through the dynamo to earth and is illuminated because there is a potential difference. Once the engine is runnning fast enough for the dynamo to start charging, the voltage at the switch and the dynamo become equal, there is no longer a potential difference hence no current flow and the bulb is no longer lit.

If you examine the Regulator and Wiring diagram Fig. 8 in the workshop manual you will see that there is no direct connection between the yellow/white and red/white wires. The fact that the dynamo is trying to motor suggest to me that battery voltage is being applied to the "D" terminal which can occur if the cutout points are welded together. However as this only happens when the ignition switch is on it suggests to me that there is either a problem in your new wiring loom or it has been connected up incorrectly.

If you are unable to resolve this problem send me a pm with your e-mail address and I will send you the procedures for testing the
dynamo and control box.

Gerald

[Tubal Cain]

With reference to my earlier post, if you click on the following web site you can download the Lucas manual for yourself.

http://www.atcc.org.nz/tcc/LucasFault.pdf

Possibly Oscar or Brian could include this site as a Wiki.

Gerald

[pbufton]

Got the exact same fault, have no idea whats going on. read and re-read the wiring diagram top to bottom, it must be a fault with the regulator?

Im almost ready to throw the lot on the fire and fit an alternator

[gemmachine]

Today I have sorted the problem but not sure how?
This is what I have done and found
I think the charging warning light was shorting out, the rubber insulation was not very good and I think the bottom contact was touching the side housing, which was why it didn't light when the ignition was switched on.
I also changed the bulbs, I had fitted 4 watt but then read that they should only be 2.2 watt I managed to get those from the motorist centre.
I also changed the regulator. Not sure if there was a problem with the old one or not. But it had the push in bullet type connections and I had trouble getting the earth wire to stay in. So I now have one with the push on crimp type terminals which is much easier.
Connected everything up and the ignition and oil lights come on but the Dynamo no longer turns like a motor, I haven't started the engine yet but so far so good.
Many Thanks to you all for your help and ideas.
I'm sure I'll be in need of your help again soon as my next project is to see whats causing a noise in the back axle
Alan

[pbufton]

for anyone else who is having the same problem, I changed my Voltage regulator and this cured the problem. When I purchased it, it had burnt out the wiring loom as someone had fitted mew brushes in the starter motor then commenced to try and rewire the tractor with negative earth, i imagine this fried a few things