Hi there I have done an engine transplant basically have a mk2 fiesta
Pop plus which had an ohv engine in it now has an 1.6 efi engine out of
An xr3i the car runs/drives/sounds spot on but the problem is I'm out
Of Ideas on the charging side of things if you start the car up put the multi-meter across the battery you will see the voltage drop until it cuts out as its not able to run the fuel pump, if you rev it the alternator will start charging to 13.52 volts then will drop again its had a new alternator so that's ok and the wiring all seems okay but there must be a fault somewhere :s pulling my hair out at this point can't think anymore so any help or advice mucho appreciated,

Cheers mike

 

put the meter's straight onto the alternator that rules everything else out
even though you've replaced it , gives you a starting point

 

When revved and then dropped does it still continue to charge or does the car cut out as soon as you stop revving?

It shoulden't cut out tbh even if it wasen't charging at all, the battery has the power the fuel pump etc needs to keep it running, so not convinced thats the issue (Unless of course the battery is in a poor state of charge then it woulden't start at all though)

Martin

 

Doesn't give me any voltage at the back of the alternator on idle not tried that when revving it though,

 

Does the battery light come on when the ignition is switched on? When you say revved how many revs are we talking?

Martin

 

is the alternator belt tight? is the battery good cus if its in poor condition it may not accept a charge
also does your battery light come on with the ignition on and engine not running

 

When you drop the revs it still charges for around a minute at 13volts but then drops to around 11 odd volts really confusing also when it is starting to charge at the 13 odd volts the battery light comes on in the car?? But when it drops volts(not charging) it goes out?

 

No the batt light doesn't come on when only the ignition on, I font know how many revs this is at as don't have a rev counter in as old dials,
Cheers

 

Where was the alternator from as from what your saying I suspect that tbh?

Reason I ask about the light is if that dosen't work then you will have a no charge situation, something most woulden't think of but it's actually a critical part of the charging circuit, however revving hard enough can start the charge process.

Yes 11V= no charge that is the battery power your seeing, for it to charge you have to see 13V+ so as to overcome the internal resistance of the battery.

Martin

 

Yeah belt deff tight man and no batt light doesn't come on withthe ignition?

 

check for a break on the small wire on the alt this controls the batt light as marty says the alt wont start charging unless this works unless revved high enough

 

Then that is a problem, check the blue wire on the back of alt although it must be connected as you say the light illuminates when running?

Martin

 

Any idea how I go about the problem with the batt light not on with the ignition? The problem is I'm only using the engine loom of the efi to basically run the engine and so on but using the original loom from dash and switches to work the lights and so on if you know what I mean this may be the problem? Really hope not lol

I don't think it can be the alternators reason being I've tried 2 on mine that I have seen working/charging on another car

Cheers mike

 

are they the right alternators for the loom tho? perhaps wires could be wrong way round to what they should be have you tried the original engines alt on your new engine?

 

The light gets it's power via the ignition switch the same as the rest of the warning lights, the earth is the blue wire which goes on the back of the alt when stationary this acts as an earth hence the light illuminates, it also excites the field windings in the alt which in turn starts the charge process, when charging the terminal where this wire connects changes so it has the same power at the alternator output terminal and thus the bulb is now receiving two lives and so the bulb extinguishes.

I think I know exactly what you have done it's just come to me, you have connected this wire to the W terminal, this is an 8V output for electric chokes or tachos on diesels which explains it lighting while the car is running (I am tired LOL ), have a look on the back of the alt for another terminal should be D connect this wire to here and I can gurentee this will sort your problems.

That being said if the car is revved to around 4000+ RPM it should start charging.

Martin

 

That's what I have on and connected up at the moment mate, i have the old alternator on with the original wiring connected, doesn't matter if I change it around

Cheers mike

 

So what terminal do you have the blue wire on?

Martin

 

Yeah I can kinda catch onto what you are saying lol I am also tired would it be easier If I take a picture of where the wires are connected at the moment and what it looks like etc..? This would be tomorrow right enough

 

LOl ok, also have a look on the back looking for a D terminal which the WL connects to in most cases, my guess is you have it connected to wrong terminal, W most likely.

Martin

 

There's 3 terminals 2 big terminals and a smaller one, the blue wire is skinny so put that to the small terminal and the thick red wires to the bigger terminals?

Cheers mike

 

Yes the other 2 terminals are most likely D and W and the WL will be connected to one, like I say I think you have this on the wrong one. The thick cable can only connect to one and usually has a nut holding it in place this is terminal B.

Martin

 

sorry about the quality of the photo's there off my phone, hopefully by looking at these someone can point me in the right direction?





cheers

 

You have the W terminal (You can see it marked on the photos) look around and see if there are any more markings, what power does the W terminal have when running?

Martin

 

im not sure what voltage w terminal has when running mate ill go out the now and have a look to see if theres any more letters on terminals etc... and get back to you

cheers

 

right the only other letter on there is a b ill edit a picture to show you which one

cheers

 

What car is this alt off? That does not look like a standard MK2 alt to me, the B is normally the output to the battery and D is for the WL or could be W, the three spade terminals look as if this is something you have done, I am wondering if this is a modern smart charge alt as this has a 3 pin connector and you have wired into this?

Martin

 

yeah you are correct it isnt a standard alternator but this was meant to be for the mk2 from the local motor factors, it did have a 3 pin connector but that got chopped off at some point and never found this is why i had to put the spade connectors onto the wires??? this alternator worked perfectly before on the ohv engine
cheers mike

 

Strange as I am pretty sure with that 3 pin config that would be a "Smart Charge" alt.

The B terminal usually would connect to the batt with a ring connector and the other terminal is for the WL, this is the standard setup for a standard alt which does not have the 3 pin connector.

Martin

 

Ok man I have an xr3 alternator there do you think I should put that one on and wire it up?

 

It's worth a try to tbh as a test if nothing else, that should be exactly the same setup wiring wise as the original would have been.

Martin

 

Sure it doesnt go onto this terminal i've ringed?

 

From what I remember mate when I took it off there was nothing on there? This is really annoying in the way it worked before but not now lol

 

Take the blue wire off and, with the ignition turned on, touch it to the earth of the engine. Get someone to check if the ignition light comes on then. If it does (which I suspect it will), then the fault is internal in the alternator.

Also, put a jump lead from the negative battery terminal to the engine block itself then run the engine. If the earth is missing from the engine to the car body, you will get this sort of issue as well as the circuit cannot be made without going through another part of the engine, normally the throttle cable or similar, creating a higher resistance which needs to be overcome.

Where have you connected the red wires to? They should go back to the battery via the starter motor.

The alternator you have there is a 45/55A one. These use a "block" connection, the 70A ones use separate bolt connections.

The "W" output will be almost opposite the "block" connection area (bottom of your picture), nowhere near where you are working.

Is the alternator turning the right way? If the alternator is running "backwards" (i.e. opposite direction to what it is designed to do), then it will not charge correctly and will try to drain back through the diodes in the alternator, hence the power loss.

 

That explains the exact alt then, what is said above sounds the most likely about the alternator running backwards, although there was a thread recently with someone asking if they could run in reverse and a couple of people said they could but it's something you can easily answer to if it's changed direction?

Martin

 

Yeah the alternator turning the correct way, yeah the red wires go back to the battery via the starter, I know the alternator has an earth from the block as put my power probe on the body of the alternator and it was an earth,I am going to try earthing that blue wire while some one checks the batt light comes on what's the story if I earth it and it doesn't come on?

Cheers

 

If you earth it with the ignition on and the battery light does not illuminate, then you have no power to the dash clocks (check the fuse which corresponds to a picture of the brake pedal) and the light is picking up power from a back-feeding alternator. If it does illuminate, then either the wire is on the wrong terminal (it looks like the right one to me) or the alternator is not functioning internally.

The basics of the alternator are that when power is supplied to the blue wire without the alternator turning, the light will be on. When the alternator starts turning (engine running) and a certain rpm is reached (usually around 600rpm max) there is enough power being generated to overcome the low-voltage diode in the diode pack and the light goes out as there is no longer an earth. The alternator then regulates between the low-power diode and the high-power diode as required. There is a third diode which prevents a back-feed when the alternator is not working (i.e. engine stopped) which prevents it from draining the battery.

When the alternator is @ a certain speed (normally over 1500rpm engine speed depending on alternator pulley size compared to crank pulley size) the alternator has enough internal "energy" to overcome the diodes automatically and will "self-charge". This is normal. This can be seen if running with a lot of power being drawn @ night when on idle, then increasing the revs slightly and the headlamps increasing in brightness. On a good battery, you would not notice this increase.

The alternator can work fine but have a diode faulty (intermitant or continuous) which will bring on the battery light, but charge within the limits.

There is a lot more to an alternator than this, but I have tried to put it in layman terms, so the above is more about principle than exact science before anyone tries to correct me on anything.

 

Thanks for all the help lads still need to rev it to get it charging but it charges on idle after that, happy enough with it doing that

Cheers again

 

Then it has to be the bulb causing the problem did you check if it worked? Will be very simple to sort, you really want it sorted as revving is not ideal, plus you have to rev hard to do so, around 4000 RPM

Martin

 

i never checked the warning light by giving the blue wire an earth as was working on my own when doing it today and couldnt check lol
think there was also maybe too much load on it for start up as had the fan hardwired from when i turn the ignition on

cheers

 

Have you tried putting that blue wire on the terminal I highlighted for you yet?

This is the one marked B, and following advice further up the page, you need it on this one...