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80 series Dash warning lights

trev.w

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Earlier this week all warning lights came on the dash,tried cleaning and making sure connector wasn't loose,no joy,so took alternator of and got it tested and repaired cos the regulator had gone and the rectifier i think he said,Iput alterntor back on and fired it up,lights still on,but as soon as I rev it they all go off,drove it it and its OK no lights and voltmeter shows its charging,but as soon as I turn engine off then back on the lights come on again until I give it a rev again any ideas anyone ?
 

Grimbo

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Check fan belts are tight...obvious I know ;-)
If all good take it back to the guys who repaired it...... explaining the problem .... it should be a warranty repair .
 

trev.w

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Already spoke to him ,gonna see him Monday,he's definitely fixed the alternator cos lights wouldn't go of and it wasn't charging before the repairs,hopefully sort something out with it later
 

Grimbo

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He's made it charge .... I often see the same issue on old tractors where the charge light will stay on until you rev the engine...
Only other thing to check is the multi plug that plugs into the alternator has good clean contacts ...I have seen them get damaged by heat especially if the diode pack or regulator has gone.... check the smaller of the wires for a good clean connection
 

Jake the Peg

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Follow the cables up from the alternator, there is a multi plug, I think under the air box, check the condition of them, and also the fuseable link at the passenger battery, although Im sure if it’s failed it won’t charge at all. Are your batteries ok?
 

StarCruiser

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Test voltage at battery terminals. Should be 14.4V or a hair under, not over just after starting. This issue, as already mentioned, is often associated with slack belts but they usually let you know by squealing. Other issues are dirty slip rings, a different regulator or stuck brushes (which usually means no charge) corrosion on the plug in the rear of the alternator is not unheard of depending which one it is.
 
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trev.w

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I checked voltage at batterys when engine not running it was about 12.5v,then when engine started it goes up to 14+V,this must mean system is charging i think?belts are ok and I cleaned the ug at back of alternator when it first packed up,also checked the multi plug under the air filter,never looked at the fuse able links tho,Drivers side battery relatively new,but other one isn't but both give same readings on multimeter
 

StarCruiser

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Charge sounds fine (though the tenths of a volt matter here) but if you have mismatched batteries you are asking for trouble. Batteries should always be changed as a matched pair from the same manufacturer. Would it cause the fault you’re describing? I doubt it but hey, every day’s a school day.
Sounds like an alternator regulator issue with it not picking up the lower voltage on tickover. I suppose that’s something else to check that it’s not too low. But that would’ve shown up before. Fuseable links will either work or not usually so I doubt it’s one of those.
 

trev.w

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Lights only on at first start up once you pull away or rev it lights go out and stay out even when idling,its just that initial start up ,going to see the guy who repaired the alternator tonight see if he has any thoughts,got me stumped
 
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Grimbo

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It's either the "exciter" wire to the alternator or an internal fault with the alternator ...
 
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trev.w

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Exciter wire?where is this and how to check it
 
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Grimbo

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It's one of the small wire's in the multiplug that plugs into the back of the alternator ....with the plug pulled out the alternator one of the wires will be 0 v with ign off and with ign on you should see battery voltage at the same wire .... it should also be able to draw a small current so try wiring up a 1 or 2 watt bulb using that wire as a supply ...it should light up , do not use anything bigger . Remember a multi meter only shows the presence of a voltage not the ability of the circuit to do any work... ie draw any amps .
Personally I think it's a fault with the alternator
 
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trev.w

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Ok I will give it a go,alternator seems to working fine,charging etc,just those lights on initial start up
 
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frank rabbets

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This used to happen back in the day when there was an alternator relay. The red light stayed red until you bliped the throttle, the relay switched and the light went out indicating the alternator was charging. Not related/clue??
 

Grimbo

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Internal in the alternator now frank and "solid state" not a relay......hence my thinking it's the alternator .
 

frank rabbets

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I thought as much but also thought it might be an early enough 80. Time has obviously passed me by lol.
 

Grimbo

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I just get confused.... ;-)
1 minute I'm looking at some massive bit of kit full of processors , CAN controlled functions etc and then today I've sorted out 2 tractors with charging faults ( MF135 and Ford 5000 ) with dynamos and VCR's ..... and have to remember to polarise the dynamo as one is negative earth and the other + earth and tried to start an old International B450 that hasn't run for 40 years....
 
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