Should there be voltage (1 Viewer)

[jolly janner]

On the relay box should there be voltage to the orange and red wire when the engine is running

 

[mitzimad]

you would think so as its marked dplus

 

[funflair]

you would think so as its marked dplus

I thought that at first but it’s quite a heavy cable for D+ so is it?

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[Lenny HB]

I would expect 12v but that box may be fed via another relay box. Converters do weird things with the D+ wiring.

 

[autorouter]

you would think so as its marked dplus

The D+ label has a 5 next to it. I think it's for the 5A fuse, the other 3 fuses also are labelled like that.

Having said that, if the relays are triggered by the D+signal, that will switch the power contacts, which will switch on voltage when the engine is running - for the fridge or split charge relay, for example.

If it doesn't switch on and you think it should, worth checking that D+fuse.

 

[jolly janner]

The D+ label has a 5 next to it. I think it's for the 5A fuse, the other 3 fuses also are labelled like that.

Having said that, if the relays are triggered by the D+signal, that will switch the power contacts, which will switch on voltage when the engine is running - for the fridge or split charge relay, for example.

If it doesn't switch on and you think it should, worth checking that D+fuse.

I’ve checked the fuses and I’ve disconnected the box .I then false fed the red/orange lead with 12v which made the step auto retract which it has not done as it should I’ve ordered a new box hope it works

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[autorouter]

Probably it's one of the relays that has failed. It might be the same relay that cuts off all the habitation circuits when the engine starts. Is that happening as it should?

Probably the relay will just unplug to replace it. If it does the habitation circuits as well as the step, you'll need a 5-terminal relay, not the more common 4-terminal type. They look very similar, the 4 terminals are exactly the same, but there's an extra one on the 5-terminal type.

If you unplug the relay you can test it by feeding 12V to the coil terminals, which should make it click. Then test that the power contacts switch when it clicks, using the ohms range of the meter, or continuity test if the meter has that option.

 

[GeoffnDee]

Have you confirmed that power is going into the interface unit , from the base vehicle, when the engine is running ?

 

[jolly janner]

Probably it's one of the relays that has failed. It might be the same relay that cuts off all the habitation circuits when the engine starts. Is that happening as it should?

Probably the relay will just unplug to replace it. If it does the habitation circuits as well as the step, you'll need a 5-terminal relay, not the more common 4-terminal type. They look very similar, the 4 terminals are exactly the same, but there's an extra one on the 5-terminal type.

If you unplug the relay you can test it by feeding 12V to the coil terminals, which should make it click. Then test that the power contacts switch when it clicks, using the ohms range of the meter, or continuity test if the meter has that option.

Relays are soldered and yes the habitation does not get cut off as it should on starting engine

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[Lenny HB]

Relays are soldered and yes the habitation does not get cut off as it should on starting engine

That only happens on Brit built vans.

 

[autorouter]

As GeoffnDee says, if you can get to the soldered relay terminals, power should be reaching one of the terminals (the COM one). It should also be reaching one of the other terminals (the NC one). It should flip to the other terminal (the NO one) when the D+ signal triggers the relay as the engine starts.

If no power at all, maybe the relay is OK and there's a problem further back with the power feed.

 

[jolly janner]

As GeoffnDee says, if you can get to the soldered relay terminals, power should be reaching one of the terminals (the COM one). It should also be reaching one of the other terminals (the NC one). It should flip to the other terminal (the NO one) when the D+ signal triggers the relay as the engine starts.

If no power at all, maybe the relay is OK and there's a problem further back with the power feed.

New box installed step now auto retracting on starting engine also the habitation 12v switches off as it should