Dave Clasper Posted September 17, 2021 Author Share Posted September 17, 2021 Hi. Well the CB I was given appears a dud (ignition light stays on all the time). Just want chech the amp meter is wired correctly. Basically a thick cable from from one of CB, B terminals to meter, then thick cable return from meter, connected to two brown wires (I assume these originally connected to One of CB, B terminals and go to main lighting switch and fuse box). Looks easy to remove amp meter, by just reconnecting brown wire straight back to B terminal?. I had heard amp meters were a bit complex to wire in?. I did a voltage test of the two dynamo cables bridged at the CB end and these were the same readings as direct from dynamo, so ok I reckon. I also cleaned the contacts on my original CB, though change. Also I assume CB earthed ok as ignition light goes out at above idle?. So, as everything works, though only from battery current, would it be a good bet to CB is the culprit?. If so I will buy a new CB, As no time to adjust mine. Does this sound an ok plan?. Thanks, Dave Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted September 17, 2021 Author Share Posted September 17, 2021 Won't let me edit. I meant to say" reconnect brown wires", to CB, rather than "wire" Quote Link to comment Share on other sites More sharing options...
glang Posted September 17, 2021 Share Posted September 17, 2021 Hi Dave, theres two ways to install an ammeter. One, as you have it, which shows the total electrical load (always positive) and the other which shows only battery load. This second is a bit more complicated to connect but the gauge will show positive and negative depending on if the battery is charging or not. The ignition light is connected between the dynamo output and battery so when the voltage of the first matches the second it goes out. I dont think the earthing of the CB will affect this although of course it will stop it functioning correctly. If your ignition light doesnt go out and as youve shown the dynamo is good then the problem is the CB is not supplying the field so as to increase the dynamo output. If the connections on to the CB are good then its voltage and current regulator contacts arent both closed as they should be. You could test this by disconnecting the CB and measuring the resistance between D and F which should be zero... Quote Link to comment Share on other sites More sharing options...
daver clasper Posted September 17, 2021 Share Posted September 17, 2021 Thanks for patience Glang. Just checking that you knew the ignition light has always gone out (except with the CB that was given to me) Quote Link to comment Share on other sites More sharing options...
glang Posted September 17, 2021 Share Posted September 17, 2021 It sounds like youre better off with the original CB as at least thats giving an output. With this I think the next step is to check its output voltage which in your case just means disconnecting (and for safety insulating) the ammeter cable from the CB, B terminals. Then run the engine (the battery will supply all the circuits via the two brown wires that are connected to the other side of the ammeter) at 2200rpm while measuring the voltage on terminal D to earth. You should see around 15v,,,, Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted September 27, 2021 Author Share Posted September 27, 2021 Thanks Glang. Will give that a go Quote Link to comment Share on other sites More sharing options...
Ben Hutchings Posted October 18, 2021 Share Posted October 18, 2021 Itching to know what the outcome was. Have a friend with a very similar problem 😅 Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted October 19, 2021 Author Share Posted October 19, 2021 Hi Ben. Not had chance to do the check Glang mentioned above. Hopefully soon and will post the findings Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted October 30, 2021 Author Share Posted October 30, 2021 Hi. Just done the above Disconnected the A.M cable from B terminal. Pulled the D cable connection back a tad, so I could connect M.M + and connected M.M - to battery earth This resulted in no ignition light and no starter? Put it back as before and got power back again Ta Dave Quote Link to comment Share on other sites More sharing options...
glang Posted October 30, 2021 Share Posted October 30, 2021 Sorry Dave, I looked at the wiring diagram again and before your ammeter was fitted 3 brown wires went to the CB, B terminal. Now I think youre supplying two of them through the ammeter and the 3rd (battery supply) must still be connected to the CB, B? Of course if this is the case on disconnecting the ammeter cable nothing will work so you need to also disconnect the battery supply brown from CB, B and connect it to the ammeter brown. Then you should have the ignition light and be able to start the engine while measuring the CB output voltage on the B terminal (even better than D terminal because it will prove the entire system).... Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted October 30, 2021 Author Share Posted October 30, 2021 Thanks Glang. Will try that, and thanks for bearing with me on this one. Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 3, 2021 Author Share Posted November 3, 2021 (edited) Just to be clear Glang. The single brown cable from terminal B (battery), to connect to the amp meter cable removed from other side/connection of B terminal,and leaving the other end of amp meter, still connected to the two brown cables, that I think were originally (before amp meter fitted) connected to the other side/connection of B terminal. So now measure votage from the now bare, CB,B terminal I think! Ta Edited November 3, 2021 by Dave Clasper Quote Link to comment Share on other sites More sharing options...
glang Posted November 3, 2021 Share Posted November 3, 2021 Thats it Dave. The power will come from the battery on this last wire and flow through the ammeter to the two brown wires connected on the other side which then supply all the car's circuits. You then run the engine and see what voltage the regulator is controlling at.... Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 4, 2021 Author Share Posted November 4, 2021 Thanks Glang. It would the same to connect single brown (battery) to the two brown cable connector and bypass the A.M. This is just a bit more simple, connection wise. Ta Quote Link to comment Share on other sites More sharing options...
glang Posted November 4, 2021 Share Posted November 4, 2021 yes same except ammeter wont read anything but ok for test purposes. Just remember nothing should be connected to the CB, B terminals and the disconnected brown wire going to the ammeter will be live... Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 4, 2021 Author Share Posted November 4, 2021 (edited) Did the voltage test at 2000 rpm. Slightly under 14 V at B terminal. Also the same reading at D terminal. Did notice the shorter and longer tube/cable thingies on the bottom of C.B, got quite hot to the touch, while doing tests. Don't know if this is relevant? Thanks Edited November 4, 2021 by Dave Clasper Quote Link to comment Share on other sites More sharing options...
glang Posted November 4, 2021 Share Posted November 4, 2021 yes those are resistors that protect the contacts from sparking so the CB has to stand away from the surface of the bulkhead and allow cooling air to circulate behind it. The reading you got is good being steady but a little low as the manual says it should be over 15v with an ambient temperature of 10ºc (or 15v at 20ºc). This means you need to adjust the voltage setting which is done by turning anticlockwise the pressed metal cam of the coil at the opposite end of the CB from B terminals. There is a special tool to do this but I was able to move mine by hand although not with the CB bolted in position. Mark the cam before you start and then move it as small an amount as possible and repeat the test. Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 4, 2021 Author Share Posted November 4, 2021 So, even though the test shows just over 1 volt short, this maybe explains why all the the previous volt tests I have ever done, only shown around 12.5 from the battery at idle (rather than around 13.5 as is the norm?) and battery always needs a charge, especially after using lights etc. I didn't quite understand what you meant, when explaining the simple way my V.M is wired (always shows the - amps bieng used, and never goes into the + side of the gauge). Is this correct for this wiring, or because the battery isn't charging?. Any answers to help me, get my head around it please Thanks Quote Link to comment Share on other sites More sharing options...
glang Posted November 4, 2021 Share Posted November 4, 2021 Yes I think what youve found could explain perfectly the issue youve had for so long and an increase in the CB voltage setting cure it👍 The way your ammeter is wired means it shows the current going to power the car so always a drain (-ve) regardless of whether its coming from the dynamo or battery. The current going to or from the battery (via that last brown wire on terminal B) doesnt go through the ammeter. If you want to monitor the battery current you need to swop the brown wires around so that the two on the ammeter are on terminal B and the battery brown is in their place on the ammeter... Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 5, 2021 Author Share Posted November 5, 2021 Thanks so much Glang for all your help with this. I will be needing to use the car a fair bit in the dark evenings and no time at all, to play around with the C.B, so have bitten the bullet and ordered a new one, as it seems likely this is the issue and worth it to me, to take a punt I reckon. Cheers Dave Quote Link to comment Share on other sites More sharing options...
glang Posted November 5, 2021 Share Posted November 5, 2021 Ok Dave and please let us know what voltage you get with the new unit... Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 5, 2021 Author Share Posted November 5, 2021 (edited) Will do Glang. That would off an already good charged battery, when idling as first port of call? Edited November 5, 2021 by Dave Clasper Quote Link to comment Share on other sites More sharing options...
glang Posted November 5, 2021 Share Posted November 5, 2021 Well best after a good run and with engine revs at 2k, then you should see over 14v👍 Quote Link to comment Share on other sites More sharing options...
Dave Clasper Posted November 13, 2021 Author Share Posted November 13, 2021 (edited) I wasen't able to go for a good run, though these are the readings across the battery, with the existing and then the new CB. Battery fully charged and not kept outside Old CB Idle=12.73 2000rpm=13.96 2500rpm=14 New CB Idle=12.86 2000rpm=14 2500rpm=14 I also did V test at new CB,B terminal at 2000rpm which = 14V (I think this should be around 15V? (didn't do this test on the existin CB this time, though was about 13.95 when I tested before). Temp outside today was 14 degrees I did notice the very apparent clicking of the contacts on new CB, never heard them on old box, could just be a different sound insulation factor?. So maybe slightly better results, though not correct. Maybe time for an alternator? Thanks Dave Edited November 13, 2021 by Dave Clasper Mistake Quote Link to comment Share on other sites More sharing options...
glang Posted November 13, 2021 Share Posted November 13, 2021 oh dear that doesnt sound much different does it. Was the voltage you measured at B done with nothing else connected to the terminal? The reading in the manual of about 15v should be achieved at 2200rpm. Perhaps giving it a decent run with lights on is the next step to see what battery volts are afterwards.... Quote Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.