Flat battery - alternator or battery u/s ?

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Peter, Once I've got the old battery off, I plan to remove both the + and - leads, clean all connections and put back. If anything looks remotely dodgy, I will replace it. I've just bought an earthing strap, with the idea of providing a separate earth between engine and chassis, probably linking it to the earth lead from the battery, to end up with a engine/chassis/battery link.

The battery has the circular tapered connectors, with the leads being held on by significant nut/bolt clamps. At present, all I envisage being a pain is getting the battery out of the car. Might make a start tonight, to assess whether I can leave the inlet manifold undisturbed.

Cheers
Mike

[Dane_Rescueman]

Re: Flat battery - alternator or battery u/s ?

Mike,
I recently stripped the engine bay looms from my Berli to rewire them for EFi. Whilst apart I noticed that the old Cortina loom had a join where the alternator cable is split to three. In addition to the alternator feed, one goes to the headlight relay unit, one goes to the battery and the third goes to the main fuse unit. (I did find a fourth that went nowhere. My diagram shows that it was for the optional extra rear screen heater - not used in the donor.) This five-way join was via a swaged sleeve and had terminal gangrene. For ages my instruments read differently depending on what services I had switched on. The battery was always going flat and at night the ignition light was glowing dimly. I replaced the heavy gauge cables, swaged and soldered them together. The difference has been remarkable.
The junction can be a sod to locate though. You will have miles of loom tape on the floor!
The above is only of use to you if you have the original Cortina loom installed. If you haven't, then ignore all!
Good luck!

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Dane
I am not altogether surprised at your findings. I have delved a few times into some of the darker corners of the engine compartment and boot area, and find little time-bombs waiting for me! Also bearing in mind the age of the wiring from my 1981 donor, as well as the various cable joining devices (original and DIY bodge-ups), it is surprising that electrical faults do not occur on a more regular basis.

A previous owner fitted a Mobelec electronic ignition system, which in reality only replaced the contact points with an electronic switch. The actual power of the spark at the sparking plug must still be normal, as this system only works on the low voltage side. I suppose the gimic of the system is that the failings of contact points are removed. However, the various wiring connections from Mobelec to Cortina wiring puts potential faults back into the system! I am just in the process of tidying things up, and getting rid of those dreadful blue plastic saddle connectors and other ad-hoc joiners. My new arrangements will have all connections in view, and not be tucked away in the dark depths of the engine compartment.

Even with my new Weber 32/36 setup, and having also fitted a new larger amps battery, starting is still not a sure-fired thing as it is with my regular Nissan with fuel injection and Japanese technology. I suspect the Piper 270 camshaft is partly to blame, but a boost to the sparks department could help things somewhat. However, I don't really want to invest in an electronic dizzy & coil. E-Bay ads for example run into a couple of hundred pounds to do it right.

While on the subject of instruments, I have never been happy with the glow I get from my Smiths ones. The bulbs by themselves give fairly bright light, but becomes a dull light once installed inside the instrument casing.

Cheers
Mike

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Mike, are you sure the Mobelec system doesn't have an amplifier as well? Don't the leads from the dizzy go to a little 'box' of some sort, with other cables going from it to the coil?

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Donnie, no little box evident. Red & blue low amp cables exit from Mobelec's yellow box, and via several bodged up joins end up on the + and - terminals of the coil. (Its the joins and cable routing I am working to improve at present. I can provide a home-made wiring diagram if it helps)

Another twin-core cable also exits from the yellow box and ends up going into the base of the dizzy. So, as far as I can figure, this cable completes a circuit to the yellow box to say that the rotor arm is in a position to fire the spark to a particular HT lead. The yellow box then completes another circuit to energise the coil - sparking then plug fires. So in my opinion, this particular Mobelec only replaces the contact points.

The main HT lead from coil to dizzy has nothing connected to it as you might think if the HT circuit was getting a boost. The coil itself doesn't look anything special.

Cheers
Mike

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Hi Mike.

I'm pretty sure your 'yellow box' is an electronic switch/amplifier. If it wasn't, then whatever type of contact-breaker switch is inside your dizzy would still be 'sparking' and would provide no benefit over conventional 'points'.

Inside this box will be an electronic 'switch' with no moving parts. As you suspect, the sensor inside the dizzy (replacing the old 'points') just gives a very low current signal to your yellow box. This then handles the larger current required to supply the low tension side of the coil - and also tends to give it an extra bit of ooomph by boosting the current using a capacitor (and other stuff!).

Everything from the coil onwards (HT side) will be standard.

I have fitted a basic 'Sparkrite' unit to my Berli which still uses the old points, so it's not nearly as groovy as your system. But - wow - it really does make starting a LOT easier, and saves on points wear.

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Hi Donnie
Now that I have had a chance to study the wiring arrangements a bit more, I am puzzled by the following: the red & blue wires that end up connected to the + and - terminal on the coil - they are joined to the usual + and - supply to the coil in PARALLEL. So that the yellow box DOES NOT make and break the circuitry.

I expected the box to act as part of a switch mechanism, triggered by the sensor replacing the contact points, interupting the LT power to the coil as required. Does this sound right to you?

Cheers
Mike

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Hi Mike.
I am not familiar with the Mobelec system, but it does seem a bit strange that BOTH the original wires are going to the coil as well as the ones from the Mobelec unit.

However, the unit MUST be doing the switching via the points replacement thingy because - well - it wouldn't work otherwise 'cos you don't HAVE points any more!

Can you trace where the ORIGINAL coil wires go? (The +ve is a live fed when the ignition key is turned on, and the -ve usually goes to the distributor where it is 'earthed' via the contact points.

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Ok, have a look at this:
http://www.geoffrey-miller.demon.co.uk/rrr/electrical/mobelec_magnum.pdf

This suggests that the cables from the Mobelec should be connected as follows:
(1) BLACK wire to earth.
(2) BLUE wire goes to coil -ve (or marked 'CB', etc) This is the ONLY wire that should be going to the coil.*
(3) RED wire goes to coil +ve (or marked 'Ign', etc.) This terminal of the coil should STILL have the original wire also going to it - this is the ignition wire which becomes live when your ignition is turned on.
(4) GREEN This should be insulted and tucked away safely - only used if original contact breaker is being used.
(5) TWIN GREY goes to the new contact-less 'triggerhead' in the distributor.

* I wonder if the wire you say is also going to the -ve of the coil might be the feed to the tacho? Can anyone confirm?

Ok, you happen to have a really nifty fully-contactless electronic ignition unit. It's a cracker! Mind you, it's only as good as how well the timing's been set up - if your timing is OUT, then this ain't going to correct it! However, once set, it shouldn't move, unless the distributor itself is worn.

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Now, that IS annoying, especially as I made a point of leaving a gap between the link and my text!!!



http://www.geoffrey-miller.demon.co.uk/rrr/electrical/mobelec_magnum.pdf

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Hi Donnie
Thanks for the link. Yes, I made an error in my Sherlock Holmes work. What I thought was an earth wire did in fact connect up to the rev counter. That makes a lot more sense, so that the blue wire to the Neg side of the coil actually serves to complete its circuit to make it fire.

I had assumed that the green/white wire saddled to the Neg coil connection was an earth. It disappeared through a grommet in the bulkhead into the dashboard area, and took a lot of upsidedown grovelling under the dash to work out where it went. I thought it a bit odd that somebody should have taken the trouble to connect to earth so remotely, when there was plenty of metal available around the engine! I was mislead also by its colour.

While I was under the dash, I found a short earthing wire to the radio had wrapped itself around the windscreen mechanism. The wire had broken, yet the radio continued to work. After a bit of effort I managed to unwind it. As the radio didn't appear to need it (probably getting an earth via the aerial lead) I did not reinstate said wire. However, I put a lot more cable straps around the various cable bundles, to stop a recurrence of the wire tangling. There is not a lot of space for so much cabling under my dash! Anyway, the misleading rev counter cable did cause me to find the wiper/cable tangle, so my time was not entirely wasted.

Haven't reconnected all cables as I write, but sometime this weekend all will be resolved. The cabling between Mobelec/dizzy/coil will be tidier, and hopefully reliable in the long-term. I've also run a new cable from Pos coil connection direct to the ignition switch, rather than rely on the old one which disappeared into the depths of the engine area.

Cheers
Mike

[Dane_Rescueman]

Re: Flat battery - alternator or battery u/s ?

Just make sure that your coil is a 12v type. The Cortinas originally had a 7v coil supplied by a cable that contained a length of resistor wire. This will be your old tatty feed which was Fords cheap way of adding a ballst resistor to lower the operating voltage.
A 7v coil will work for a while at 12v but will eventually overheat. Good luck!

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

Hi Dane
Not sure what voltage my coil runs at. There was no resistance wire or other gizmos on or around the unit, and unfortunately it is mounted very low in engine compartment to readily check what is stamped on the body. Might jank it right out and check, just to complete my education!

When I last had the plugs out, I connected one to an HT lead, wedged it against the engine (for earth connection) and spun the engine on the starter. I was not over-impressed by the power of the sparks. I've seen 'super' coils in eBay for around £30, and wondered whether I should just take the plunge and get a new one. Bit of a puzzle as to what to go for, if at all!

Cheers
Mike

[gouldsborough7]

Re: Flat battery - alternator or battery u/s ?

I took the coil off my Berli as I knew I would. Had to know what type & voltage it was. It was very awkwardly fitted (no surprises there!) but off it came. Apart from dirt, there was nothing at all to identify the make or model, being just a shiny aluminium casing with threaded studs onto which the + & - terminals push on. The HT lead is a push-on as well, so I don't know whether anyone can recognise this.

Ended up looking on various web-sites for a potential replacement, and Demon Tweeks appeared to offer the best choice. I could buy a sports coil apparently producing hefty sparks when you most need it: cold starting, wet plugs if over-choked the carb, accelerating, you name it. Then somehow, this technology would reduce the sparks to something like normal for cruising. All for about £45 I think.

Might take the plunge with a new coil if the car gives me any more bother when starting in this cold weather.


Cheers
Mike

[macdonald.dm]

Re: Flat battery - alternator or battery u/s ?

Whatever coil you might go for, you'll still need to know if it is 12V or lower. I'd have thought that the resistance measured across the +ve and -ve terminals should give a good guide, but I've no idea what sort of values you should be looking for. perhaps someone at demon Tweeks can help?

If you disconnect the HT lead from where it enters the distributor cap, and place this end sitting a good quarter to half-inch from an earthing point (but away from the carb and other petroly bits...), a spin of the starter should see healthy sparks easily jump this gap, especially from an electronic system (it can be a bit hard to judge how good the sparks are across a small plug gap.)