trickle volts trigger relay

Hi,

Fitting after market driving lights to work only with high beam on a 1987 Subaru Leone. It is not the usual easy relay hook up as both pos+ and neg- is switched by factory headlight switch. Simple relay in use for the driving lights.Battery pos to terminal 30, dr lights to terminal 87 terminal 85 is on the earth wire of the headlight, terminal 86 is getting the 12 volt power from high beam circuit but the problem is that high beam circuit also gets 1.3 volts trickling in when low beam is only one switched on. This 1.3 volts is triggering the driving light relay when on low beam. relay used is jaycar cat# SY4077. Is there an electronic component that can be added between terminal 86 and its wire to stop the 1.3volts triggering until 10 yo 12 volts is supplied.

thankyou

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my other car is a SUBARU too!

You can try adding either a diode (or two) in series to create a voltage drop or just use a standard Bosch style automotive relay - they usually need around 9 vdc to trigger.

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Kevin Pierson

Thank you. By adding a diode or two in series that would be in the wire that has the 1.3volts is it and not between 85 and 86? Any suggestion as to what type or size of 'diode'. My use of diodes in the past is limited to a crystal radio 34 years ago. I understand what they do, maybe not exact use or placement.

I will try a Bosch style relay next as the tyco and ford do the same. I was surprised the relay pulled in in the first place then more so to find the voltage only 1.3. exclamation mark

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my other car is a SUBARU too!

A 1A diode inline with the 1.3vdc wire should work great.  The current draw of the relay should be less then 200mA so 1A is a good number.  The diodes, in theory, will drop the voltage going across them by ~.7vdc.  Two of them in series will drop ~1.4vdc.  That is why you may need two, it all depends on the actual voltage drop of the diode you use and the min pull in voltage of the relay.

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Kevin Pierson

Bosch is now Tyco.   But we all still call them a Bosch relay.   I am surprised that it is energizing with that low of a voltage.   Each diode you put in series will drop about 1/2 of a volt.

The pull in voltage of a 12V relay has to be more than 1.3V. The drop out voltage is lower than the pull in voltage, but I'd expect even that to be more than 1.3V.   Are you measuring this directly at the relay coil?
If you disconnect the relay, what voltage do you measure on the coil inputs at the time you notice the problem of it energizing?