fridge van ign on wiring

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=119457
Printed Date: May 15, 2024 at 3:22 PM

Topic: fridge van ign on wiring

Posted By: ashbash171
Subject: fridge van ign on wiring
Date Posted: January 19, 2010 at 8:11 AM

Hi there ive got a merc sprinter fridge van and i need a way to wire up the ignition so that when i start it up i can flick a switch and the ign will stay on when i take the key out and also need the so when i press the brake it cuts out
Any help will be much appriciated
Ashley posted_image

Replies:

Posted By: hotwaterwizard
Date Posted: January 19, 2010 at 8:23 AM

ashbash171 wrote:

Hi there ive got a merc sprinter fridge van and i need a way to wire up the ignition so that when i start it up i can flick a switch and the ign will stay on when i take the key out and also need the so when i press the brake it cuts out
Any help will be much appriciated
Ashley

pulse on pulse off

a push button to turn it on and the break switch to turn it off

posted_image

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: dualsport
Date Posted: January 20, 2010 at 7:47 AM

hotwaterwizard wrote:

That'd do it, but the diode up top needs to be flipped around to latch-

Posted By: ashbash171
Date Posted: January 20, 2010 at 4:05 PM

Many thnx john but i am not clued up on relays, car electrics fine but relays not, could you simplify for eg where it says latch unlatch??????

kind regards
ash

Posted By: hotwaterwizard
Date Posted: January 20, 2010 at 9:15 PM

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: hotwaterwizard
Date Posted: January 20, 2010 at 9:22 PM

Dualsport --The top Diode is not there to Latch

it is there to isolate the load from the latching circuit.

The Load may keep the contacts latched without the reverse Diode.

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Posted By: ashbash171
Date Posted: January 21, 2010 at 3:55 AM

Many thanx for that John, will try it at weekend and let you know how i got on
Ash

Posted By: dualsport
Date Posted: January 24, 2010 at 10:14 PM

If the latching input is momentary, what keeps the coil of the left relay on when it's removed?

If the diode is placed as shown, it would block the current from the 12V input from flowing back through the 87A-30 contact path of the second relay, which is needed to latch the left relay.
If you want to isolate the load, you could put the diode in series with the output rather than between the relays, but then you'd have to make sure the diode is sized to handle the load. Might have to be pretty hefty if it's a fridge.
Doing away with the diode altogether would be another option. I wouldn't think the load would source 12V, so it really shouldn't be a problem.