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Electrical relay

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prb51

prb51

Luke Skywalker
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I've an issue with a modern car...with a multi function elec relay.
I have intermittent turn signals, if I mess with the relay connection I can 'revive' them...
Do relays sometimes work then not or are the alive/dead units.
I'm thinking it might be the cnnection below the relay box.
 
I hope someone that knows about relays jumps in here, as I have questions regarding the addition of relays to my LBC, purportedly to make old switches and wiring last longer. Thanks for posting.
 
The earlier relays were electro-mechanical with no solid state components. They were reasonably reliable and cheap to replace. Think of the horn relay in a TR-6, fairly primitive.
Modern relays can be electro-mechanical, solid state or a combination of both and can be expensive to replace. If you have the type that plugs into a socket and operation is intermittant, you may have a bad connection caused by misaligned pins. Pull it out of the socket and look at it under a mag. glass. You may be able to carefully straighten any bent pins.
 
Dale said:
I hope someone that knows about relays jumps in here, as I have questions regarding the addition of relays to my LBC, purportedly to make old switches and wiring last longer. Thanks for posting.
Click to expand...

Adding a relay is easy. They work as a switch to switch power directly from the battery to a device, like a horn or headlight. Without going into wiring diagram (since I don't have time to diagram right now), here's how they work:

1) One wire for 12v+ power is attached with a fuse to the battery or fuse panel. One ground wire attached to earth (a metal part of the body.)
2) The hot wire from the original switch that presently routes to the device (like the headlamp or fog lamp) goes to the relay and acts a a trigger. So when you switch the original switch, it powers up the relay to and it triggers the relay. Then the relay switches 12V from the wire that comes from the battery in 1) directly to
3) the output wire of the relay. This goes to the headlamp or fog lamp or whatever.

The advantage of this is that the POWER needed to power the device bypasses your wiring harness. The power used through the original wiring harness is minimal since the only LOAD on the wiring is that needed to switch the relay. The relay itself handles the load (most are rated for 30-40amps).


Read through this when someone posts a diagram and you'll quickly understand the mystery of relays solved.

hth
-Pete
 
prb51 said:
Do relays sometimes work then not or are the alive/dead units.
Click to expand...
Relays can certainly be intermittant; either broken conductors inside the case or dirty/burnt contacts. Sometimes, wiggling the wires can move the internals enough to make them touch down. But I'd say the odds are slightly better that the problem is external.

Dale, you might want to start a new thread with your specific question. Lots of folks on here with experience (I'll be adding some relays to my TR3 soon to convert the tail/turn lamps into tail/turn/brake lamps without modifying the original harness or lamps), but it's a lot easier to answer a specific question.

One good example (with pretty diagrams) is at
https://www.danielsternlighting.com/tech/relays/relays.html
 
I too have added relays for the headlamps on the TR4 (to spare the switch the full load) and to the brake lights on the TR3 when I added addtl lights.

Open a new thread and I will post some pics if what I did is of any help.
 
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