Relay Question

[madzie71]

Mga paps,

What is the common cause of busted relays?

I was checking my cars lights this evening when I suddenly found out that the fog lights and the secondary horn (Stebel Nautilus) would not function.

The setup is that both are turned on via Bosch SPDT 30A relays (one for the fog lights and one for the horn). The relays have separate switches (dapat lang naman... hehehe) which get its power from the accessories (ACC) of the car. I installed a 10A fuse before connecting them to the accessories (ACC) cable. From the batteries each connection is also protected by a 30A fuse.

This is how the relays were connected:

85 - ground
86 - +12 from ACC
87A - +12 from battery
30 - +12 to fog lamps/horn

I just find it strange that both relays would be busted at the same time. BTW, the fog lamps were installed about a month ago and the horn two weeks ago.

Is there something wrong with the connections I made to the relay? In my readings naman, 85 and 86 terminals can be interchanged as well as the 87 and 30 (since I am just using a single-pole connection).

Should I install a diode (maybe 1 or 3 A rating) to terminals 85 and 86? I did such in the audio setup to run the remote terminals of two amplifiers instead of getting the power-on signal directly from the HU.

Sensya na medyo mahaba... thanks in advance...

[StraightSix]

Tama naman wiring mo ... other than the overrated fuses.

Automotive relay coils usually need less than 1A, so 10A is an overkill. I don't have a Bosch SPDT right now, but a Bosch SPST needs only 150mA. With a 10A fuse the coil may fail without the fuse popping.

The Nautilus is rated at 18A, so a 20-25A fuse might be more suitable than a 30A fuse.

As for your fog lights, a pair of 55w lamps will need just about a 10A fuse.

Placing a diode across the relay coil might help, but AFAIK it only prevents any spike produced by the coil itself when turned off from going back to any semiconductor circuit and damaging it. You only have a mechanical switch ...

Moisture and heat usually cause a relay to fail, besides overvoltage and current overload. Make sure all connections are tight and soldered, if possible.

HTH