What can cause a DC relay to click on and off continuously?

[silverman166]

My caravan is equipped with two 02.024b 12v dc 30A mini change-over relays which are designed to operate only whilst the caravan is being towed ie activated by the voltage supplied from the car only whilst the engine is running. One enables the caravan battery to be charged and the fridge to keep cool whilst towing, whilst the other cuts out other electrics within the caravan whilst towing.

The caravan battery is used to power a motor mover to enable me to park it at home, but I find that the battery has insufficient charge after a 3 hour journey home, despite having been fully charged whilst on site.

I've found that the two relays are clicking on and off continuously every few seconds, but when testing each relay via a 12v battery when removed from the van they seem to be OK.

Would a poor earth connection within the van produce this effect, I'm wondering, but quite how or why I'm unsure?

Any suggestions gratefully received.

 

[Bluejets]

Bad earth connections in automotive are a fairly common problem and can lead to all sorts of feedback problems.
It is almost impossible to say just which bad earth could end in your present situation but it certainly sounds like it.
The every few seconds sounds like it running back through an indicator relay.
The bad earth though could be anywhere and the wiring diagram is not much assistance as the actual wiring may follow different paths.
Auto leckys usually have a 6th sense for tracking these things down.

 

[silverman166]

Thanks for your most useful comments, Bluejets. Looks like I've got a lot more investigating to do!

 

[silverman166]

PROBLEM SOLVED!!
Took some finding, but eventually I deduced that two connections to the relay were incorrect, so not an earthing problem at all.

 

[Bluejets]

All being equal, it's almost impossible for us to diagnose incorrect connections.
It's the reason that it is often asked to supply what you have rather than what it should be.

 

[silverman166]

Yes, I fully appreciate what you're saying, and apologies if my approach caused disgruntlement.