Bypassing exciter wire - Temp bodge

[damageandy]

LONG EXPLANATION AS TO WHY

Battery light came on my T4 2.4D, no charge to the battery, did checking today tracing previous repairs ect. The exciter wire is only getting 6v when disconnected and reading 2-3v when connected - not enough to engergise.

I'm believing its the clocks at fault after stripping down and checking I'm getting the same voltages (as above) directly out of the clocks and the battery light is dim when compared to the others.

Alternator is ok, i gave the exciter terminal a quick 12v and it started charging fine. I could do with bodging this until i can find some replacement clocks.

QUESTION

Can i simply just use an ignition live feeding a relay to provide the exciter terminal 12v? or will it need a diode or bulb to drop the voltage slightly?

Its only a temp measure so i can get to work and until some new clocks arrive and i don't need the
battery warning light to work.

Cheers.

[jifflemon]

The exciter circuit is simple enough; Ignition feed to the dash bulb, it earths on the alernator.
Once the alternator starts to charge, you've 12V on either side of the circuit, so the bulb goes out.

Simple enough to do a temporary bodge.

[retrowrongun]

Check the bulb for the battery light in the clocks
A lot of cars need the bulb to complete circuit

Have seen a simple bulb swap cure this so surely worth a try as one I did had a crappy connection on the ribbon circuit board on back of clocks were the warning battery light bulb went

[bortaf]

what voltage are you getting INTO the chrging bulb ? it could just be the bulb if you get 12v in and less out ?
The charge light into the alt is what makes the alt start to charge as it excites the field windings till the alt is up to speed so it can charge then once at speed it excites itslef (lol) then as above 12v + 12V = lamps goes out.
i have jumped exciters as you say but i allways used a bulb in ciruit as it acts as a resistor i believe, tis why you cant use an LED as an alt lamp wothout a resistor adding in the feed.

[cobblers]

Just repair the clocks Andy - take them apart, resolder all the joints for the socket and any others that look suspect (there might be a resistor for the exciter).
I've done a handful of these, quite straightforward to fix.

[damageandy]

bulbs fine, checked and swapped to make sure.

10v (10v regulator on clocks) at the bulb on the clocks - 6v out of the plug, t4 clocks are notorious for poor solder joints.

[retrowrongun]

Well surely sorting a few dry joints is easier and much better option than bodgeing the excitor ?

[damageandy]

Cheers for the replies, ive bodged it now.

As said temp bodge to get to work. Not enough time or daylight to strip everything, check, solder them, refit on the chance it may work when i can just run a simple wire and definitely get to work and then fix properly on my day off.