Driving lights staying on ???????????

Are you using the old style with the points contacts or the new ones with the blade fuses ????

Old ones regularly needed a points file stuck through them in damp conditions ......

Mine has 2 blade fuses; (both 20amp)

Now there's a name from the past "New Era"

I used them years ago on a couple of earlier landcruisers I owned.

They seem to develop that problem over time were one, the other or both relays stick.

I went away from them for that reason.

I think what happens is they metal core of the relay coil is closer to a mild steel than the high silicone steel generally found in motors, contactors, relays and transformers.

Over time the core appears to me to become a permanent magnet of just sufficient strength to hold the relay closed without power on the coil.

If my theory is correct Bill you could recover the relay by running it with the switching wires reversed in polarity for a while.

Hang on, that may be difficult as I just remembered the New Era uses the case as the negative. It still could be done but it's not a matter of just swapping a couple of wires.

Geoff

Thanks Geoff.....I "think" you might be referring to the older style "New Era" jobbies. The current batch aren't earthed through the shell/body/mount, but I have never dismantled one to see what state the contacts are in.

I guess I may have to replace it with 2 separate Bosch or similar type single relays.

Cheers mate

Roachie

Hi Bill,

As I said earlier, I went away from the New Era's for the exact reason you are describing.

But if they've redesigned them so that you can reverse the polarity of the coils I'd give it a go!

You've got nothing to lose and it's a heap cheaper than buying new relays!

Looks like I need to revisit the New Era's as that was my biggest problem with them, apart from that I thought they were reliable and very well made.

Geoff

Why would fuse rating have any impact ?

The fuse has to be rated to take the continuous current - when the contacts weld shut, the current drawn is exactly the same as when the relay is switched on normally.

Hi Mike R,

Simple. The fuse fitted may be rated a bit higher than recommended. Excess current *could* conceivably "weld" the relay contacts shut but not necessarily blow the fuse straight away. Hence the lights stay on, because the switching cct of the relay is ineffective as the contacts are already stuck together keeping the lights on..

Hypothetically, if you had a relay designed to handle a continuous load of 25 Amps, but had it in a cct with a 35 Amp fuse, what would give out first? I'd suggest the relay contacts would. It could possibly weld the contacts shut but not actually self destruct in the short term. Given that the contact area of a relay is likely to be tinned, it will melt long before the copper it is attached to - and weld themselves together.

Fuses by nature are designed to blow very quickly and save the cct their installed to to protect from damage. On the other hand, a relay is designed to handle large currents (within their design limits), and are usually over slightly engineered to handle a current above what their ultimately advertised to handle. Therefore, they might not self destruct straight away. But if the wrong fuse of a higher rating is placed in the cct, the relay *could* become
the "weak link".

Fuses are by default, designed to be the weakest link in the chain. They are designed to blow (go open cct) before anything else in the cct is affected. But if a fuse of an excessively high amperage is fitted to a cct not designed for it - all bets are off.

Apologies if I have over simplified for you, but this but an option for Josh to look at.

Cheers, Matt

. . . so if a fuse had blown, he should have taken it as a warning to put in a higher rated relay ????

Mike R,

Higher rated relay? No, (and my name is Matt by the way),

Given your detailed responses elsewhere in this thread, you know what I'm about to say.....................

A typical spotlight relay is 25 Amps. A pair of 100 Watt driving lights are ~ 16 Amps.

I'd be looking at why the relay welded itself together. And that in itself is hypothetical until such times Josh informs us otherwise.

But simple logic dictates (at least, in the world I live in), you'd check the fuse first (and if I saw something bigger than 25 Amp I'd be concerned), then the relay, then the lights (and associated wiring), and all earthing points including the battery and lights themselves.

Hey, I'm probably wrong, but it's all part of fault finding - and the idea of that is to systematically eliminate components of the cct until you isolate the culprit. Yes?

Matt.

Yep - reminds me - just bought a relay the other week to get some air horns going that I've had for years - surprisingly cheap for what they do - 30A about $14 I think.

Jaycar sell a 150 amp relay for $19.

http://www.jaycar.com.au/productView.asp?ID=SY4073

My Driving lights seem to flash on for a second when I turn on the headlights everytime ?
this is happening with a brand new twin blade fused New Era Relay.
What the ?????