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Alternator Exiter Wire Issue?

Discussion in 'Mondial' started by Bell Bloke, Jul 28, 2019.

  1. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Hi Chaps and Chappettes, hope you are all well and making lots of Mondial Memories!
    We've been busy using Kato clocking up the miles, having lots of trouble free fun until.....now.
    Minor issue I'm sure but electrics are not my thing really so here goes.
    The very cheap alternator a bought 4 years ago stopped charging, so blaming that I replaced it with a Bosch one and having fitted it today it also does exactly the same thing.
    1.Symptoms are start Kato, voltage to battery reads 12.3 volts and then drops steadily down to 11.2 ish as it's running.
    2.Before start up the battery light is ON and goes OFF as it is started- so that's correct.
    3.Voltage actually at the alternator is the same as at the battery- so that;s good too.
    HOWEVER on measuring the voltage at the D+ terminal with ignition ON the voltage is only 1.6volts! Is that correct shouldn't it be 12 ish volts? I have to be honest I don't really understand how alternators work or regulate the voltage so as no to overcharge the battery.
    Your high voltage input would be greatly recieved Folks!
    All the best Bell.
     
  2. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    OOps sorry misspelt the title!!
    Also forgot to add importantly that the 'Exciter Wire' that goes to D+ is only giving 1.6 volts with the ignition on but not engine running...
    Shouldn't it be 12volts? and if so why does the battery light work as it should..
    Regards Bell
     
  3. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    Normally the voltage regulator is an internal part of the alternator- are you getting the alternator warning light on ?
    With the engine running you should be getting about 14.4 volts across the battery terminals as you need more than 12 volts to push it in.
    Looking at the wiring diagram ( do u have a copy) the power cable from the alternator goes to the starter motor ?and the starter motor cable goes to the battery- ie in series. Check the condition of the connections at the starter motor as it will stop the battery charging if dirty or burnt.
    What do you mean by the exciter wire going to D+
     
  4. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    Look on left side of engine bay for a connector block with 2 wires- 1 x white and 1x yellow with green stripe( this is connector C3) check the connection on the yellow green wire
     
  5. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    OK Mike, I'm there and it's corroded, am cleaning it up now. What else does this plug do, when I dissconnect nothing changes which can't be good ha ha.
    I noticed that the battery light doesn't light when unplugged also. Regards Bell.
     
  6. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    I can e mail u the diagram if u dont have it
    It is just a terminal block and the white wire is the 12 volt signal to the solenoid to engage the starter, the yellow green goes to the alternator. The diagram shows another connector in the yellow green line between the one u r in and the alternator. Might be an idea to connect a multi meter to the wire- disconnect the yellow green from connector in engine bay and from alternator- should be next to no resistance between them. The light will not be on as the circuit is open when yellow green disconnected.
    I am thinking you need to clean main power cables on starter motor solenoid next
     
  7. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Hi Mike, right I'm back on it this morning and I did what you said and the feed from the front of the car is good with a fairly healthy 11.6 volts on a 12.2 volts at the battery. However when the plug is connected the feed to the alternator is only 1.6 volts! So I just need to find out where it's being lost now- I don't think it's in the plug now. However this has massively narrowed down my problem to just the engine bay wire run. I can't thank you enough for all your help in pointing me straight to the problem area. So now I guess it's the starter motor area? I will report back asap. All the best Bell
     
  8. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    #8 mike32, Jul 29, 2019
    Last edited: Jul 29, 2019
    Send me an e mail address and will send you the wiring diagram as shows it very well
    Take the small wire off the alternator- with the key on, you should have the battery voltage on the alternator end- compare it to battery volts. This wire is telling the alternator the system volts- ie the voltage sensor i think.
    Next look at fuse box- look at the last vertical row of relays on the right hand side, to the right again is a vertical connector- should be 2 red wires 51+52. Check they are good connections. This is supplied from the small red wire on the positive battery terminal, which splits into 2 wires 51+52. Should read battery voltage
    Any volts you are measuring on the alternator line should be present battery volts, if not you have a bad connection. If this does not work the ignition switch may be part of the problem as this is in the circuit
     
  9. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Thankyou Mike that's brilliant. I will try and get back on it today if possible, in the meantime I'll send you my email address. All the best Bell
     
  10. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    You can buy the wiring diagram book off me if you want as i dont have a use for it any more. Cost me £70 over 22 years ago.
    Wiring diagram for 3.2 mondial- reprint by mar parts ltd. pt no 95990845
    Make me an offer and can be in the post today
     
  11. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Hi Mike mine is a 3.0 QV. All the best Bell
     
  12. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Well Mike, I'd just like to say thankyou for singlehandedly helping to sort out this issue. The circuit diagrams which you labelled for me and sending me to the plug in the engine bay pretty much got me straight to the issue and I have to say it's an odd one.
    The actual reason for the alternator not charging was that the 12volt exciter wire to the alternator that read 1.6 volts not 12 was obviously the issue.
    You telling me about the engine bay plug meant I could get a 12volt reading there, and thereby cut out all of the loom back to the fusebox and ignition switch.
    This meant that the issue was between the engine bay plug and the alternator. What I found was that 2 inches of the exciter wire at the alternator end, although not broken at all and looking to be in good condition had gone very high resistance. Once I cut out the bad bit and replaced the plug I got my 12 volt feed back and obviously everything is now working great. However I've never come across a wire that looks to be good in everyway but is actuallly acting like a resister!
    No doubt electronics Gurus will see this all of the time...
    Anyway many thanks again Mike, I'm just in time to take Kato to the steam fair tomorrow...excellant!
     
  13. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    I have had my head out the door listening for the alternator running, nice to see it sorted.
    I dont think the electrics on the 3 and 3.2 will differ much- last chance on the wiring diagram book then !!
    Steam fair- great as i am a time served Steam Turbine engineer.
     
  14. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    ARRRGG!! Out today and not working again....
    OK latest tests reveal.
    1. New alternator when current measured from the alternator itself is NOT generating.
    2. It's an exciter wire issue I'm sure.
    When the exiter wire voltage is measured (igtnition ON) it reads only 1.6 volts however disconnect it from the alternator and it goes upto 12Volts.
    In other words under load the voltage drops. This must mean high resistance SOMEWHERE...
    3. Engine bay plugs are good so the resistance must be further along towards either the FUSE/RELAY board or the IGNITION switch.
    That's unless there are any other plugs I don't know about along the way.

    So, not understanding much about electrics I'm guessing that the voltage to the alternator must be 12volts with the ignition on?

    Also I've looked for the YELLOW/GREEN banded wire at the fuseboard and can't find it, any ideas Guys?
    Hi Mike, it looks like I'll be needing that diagram if you think it will cover the 3.0 car :)
    All the best Bell
     
  15. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    Take the alternator out and have it tested, if the volts are falling off the cliff it might be a problem inside the alternator.
    Other idea is to run a temporary wire from the battery terminal to the alternator- if the present wire has a fault on it, it will drop the volts. As you take the wire off the alternator they is no current flow as open ended wire, and you will get 12 volts at no load.
    I will have a look to see what yellow/ green does. Earth ?
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,326
    Texas
    Full Name:
    Steve Magnusson
    #16 Steve Magnusson, Aug 11, 2019
    Last edited: Aug 11, 2019
    +1 -- that would well match your symptom/measurements. This link should get you a pdf copy of the euro version Mondial QV wiring diagram (see Fig 1):

    https://www.dropbox.com/s/shgl3mh5nmmfqcw/Wiring Diagram Mondial QV Euro Version.pdf?dl=0

    Interestingly, this signal doesn't pass thru the fuse-relay panel, but it does pass thru the C5 connector, C3 connector, and one unlabeled connector in the engine bay.
     
  17. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    Looking at the diagram wire GV also connects to the monitor check control which i assume is the display on the central console. Shows 3 sets of terminals- all 1 to 6.
    GV is connected in and out of the 2nd set, on terminal 1
    GV being the wire between the battery and the alternator
     
  18. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Just to say Chaps that the alternator is brand new and is doing the same as the old alternator that was probably OK in the first place...
    The other stuff I will check out and report back. Cheers Chaps :)
     
  19. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    How long did the alternator work for after you changed that bit of wire
     
  20. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    Hi Guys, sorry but the weather here has been awful and I need to get Kato outside to work on him.
    The alternator was working for about 10-20 miles and then the voltage drops off. I think though that is related to the fact that I
    charged the battery, so it's a kind of false positive.
    I will get back on it as soon as possible and report back. Many thanks Chaps.
     
  21. mike32

    mike32 Formula 3

    May 13, 2016
    2,080
    Uk
    I had my head out the door listening for Kato running, to no avail
     

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