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Posts: 21
Joined: Thu Jul 18, 2019 6:36 pm
Location: Perthshire


Post by Mossop » Sat Nov 02, 2019 1:47 pm

Hi folks looking for some advice, I've got a 990 selectamatic , when I purchased the tractor the warning lights were all smashed so I have bought replacements from Barclay Williams , after rewiring when I connect the battery all three glow dimly , when I switch ignition on two of the lights go out and the hydraulic light glows brightly , I also noticed the dynamo starts to feel warm , I haven't done anything except wire up the lights according to the wiring diagram , done a continuity test all ok , help much appreciated as electrical to me is like understanding wizardry , thanks

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Joined: Mon Oct 13, 2014 8:20 am
Location: Vallentuna, Sweden

Re: Electrics

Post by rid54 » Sat Nov 02, 2019 3:31 pm

Something is obviously amiss here. The warning lights are all fed with +12 V when ignition switch is in the "run" position. They should all glow "brightly" at that point, as long as the engine is not started. With ignition turned "off", they should all go out.

The lamps are grounded by their respective chekup duty; that is:
the oil lamp is grounded by the oil switch when there is no oil pressure; oil pressure good = no light
the hydraulics lamp is grounded by the "suction switch" that tells you if the filter is clogged; filters good = no light
the charge warning lamp is grounded through the dynamo armature; dynamo charging = no light
There is no normal situation when the lamps glow as soon as the battery is connected.

If hooking the wires up according to the diagram doesn't make things work OK, one may have to consider if modifications have been introduced, that have changed the actual layout from the original build. Is the dynamo the original dynamo or has it been exchanged for an alternator? Are all chassis connections (earth, battery negative) healthy? If there actually is a dynamo (original setup), is the regulator OK?

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Joined: Thu Jul 18, 2019 6:36 pm
Location: Perthshire

Re: Electrics

Post by Mossop » Sat Nov 02, 2019 3:49 pm

Hi , yeah it's definitely a dynamo , has had a new starter by previous keeper , as said all the warning lamps were broken when tractor was bought , for some reason the yellow hydraulic light has three wires, brown and green joined together with a brown and yellow then a green cable but that is the way I cut them of the original lamp holders

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Location: South West Finland

Re: Electrics

Post by ollek » Sat Nov 02, 2019 5:08 pm

There is a diode in the system. The diode is fitted in one of the ground leads for the hydraulic warning light lamp. The diode is open for ground trough the diode to the alternator when the alternator is not charging. This enables the driver to check that the bulb is OK as the light will be on when the key switch is in the on position, without the engine running. The other ground lead from the lamp is connected to the suction switch under the pto housing. The lamp will go off when the alternator starts to charge and the voltage is the same on both sides of the diode. The hydraulic filter is blocked If the lamp turns on when the engine is running.

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Joined: Wed Sep 24, 2008 8:17 am
Location: Suffolk

Re: Electrics

Post by SteveCollett » Sun Nov 03, 2019 9:35 am

it is quite common for the hydraulic filter light to stay on for a protracted period if the oil is not hot, in fact commonly all day if on light work. This is not an issue just shows the oil is not going through the filter that fast.
Ollek is correct that it does show the filter is blocked if the oil is hot

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