I own a 1984 MK2 ford fiesta popular that didn't originally come with a time clock because it's the most basic model but has the slot for it.

I've managed to source one from a MK2 Ghia model with the intention to wire it into the existing loom assuming it would just need a permanent live and earth but it turns out to have 4 connections and I have no idea what any of them are.

Is there an electrical Wiz on her that could tell me what connections I need on the back of this time clock to get it to work?

Many thanks!

I think I would look in a Haynes manual, but probably Earth, Permanent 12V, switched 12V, and 12V from lights.

Earth and permanent to keep the clock going, switched 12V supplied so that you can adjust, and 12V from lights to dim the dispaly at night.

Haynes manual (1030) does show the clock with 4 connections, and that it has an internal illumination, but the circuit diagram is a bit of a maze, and of course just gives you colours of the cables.  And you are highly unlikely to find a 40 year old car in a scrapyard where you might find a cable loom.

If you can find which of those four pins is 0V by inspection of the pcb, then you should be able to put 12V on the other pins and see what they do.

Very long time since I have looked at pin outs on a IC, but I think that the pin on the bottom right (as in the image)of the NEC IC will be 0V........ and one side of the electrolytic will also be 0V.

Very good advice from Paul.

My best guess is terminal 'IO 1' will be ground, but you need to check it using a multimeter. Go between the negative of the electrolytic capacitor and the terminal and it should be Zero Ohms. If it is then you have confirmed the negative, and it's then just a guessing game with the other 3. They will all be 12V positive so no harm in connecting them all for a test.

See diagram below:

 

 

19 hours ago, Paulkp said:

I think I would look in a Haynes manual, but probably Earth, Permanent 12V, switched 12V, and 12V from lights.

Earth and permanent to keep the clock going, switched 12V supplied so that you can adjust, and 12V from lights to dim the dispaly at night.

I'll have a look in my manual and see if I can suss it, forgot I had one lol

To be honest I figured it had a permanent live, earth and possible a switch live from the dash lights but it's the fourth connection I couldn't really get my head around..

Ill see if I can get it going with just the 12v supply and earth!

 

17 hours ago, unofix said:

Very good advice from Paul.

My best guess is terminal 'IO 1' will be ground, but you need to check it using a multimeter. Go between the negative of the electrolytic capacitor and the terminal and it should be Zero Ohms. If it is then you have confirmed the negative, and it's then just a guessing game with the other 3. They will all be 12V positive so no harm in connecting them all for a test.

See diagram below:

 

 

Perfect thanks alot. I'll set a 12v rig up and give it a go!