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Need a 2 second delay on a 12volt wire


dr_bowtie
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E-Fan%20Diagram.jpg

 

 

 

 

Ok here is the thing....this is my set up sort of...as you can see I have a Thermal Switch that turns on my Electric Fans whent he water temp of the engine gets up to 170f....

 

the probe wires are on a probe that senses temp then basically touches the 2 wires together to create a circuit that turn on the 12v positive trigger wire (Green wire). This trigger wire energizes the relay windings that closes the relay to send power from 1 red wire to another thus turning on the fans...

 

now the switch appears to be voltage sensitive and the load of trying to start the fan drops the voltage just enough to mess with the switch turning on the trigger wire full....thus rapidly turning the trigger wire off and on and making the relay stutter thus burning up the relay contacts in a month or so...

 

 

what I need is to somehow put a Delay on the trigger wire in between the Thermal Switch and Relay....so that when the Thermal Switch turns on the trigger wire (Green wire) it actually takes a few seconds before it actually turns on the relay....that way the switch fully energizes the trigger wire Before it triggers the Relay....

 

any idea what I can splice into the Green Trigger wire between the Switch and Relay to give me that few seconds....feel free to redo my MS-Paint drawing to show it

 

 

 

E-Fan%20Diagram1.jpg

 

this is sorta what I need to do... :)

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Is a two second delay going to solve the problem? You are just making the fan start two seconds later than the thermal switch tells it too, will this not still drop the voltage at fan start and cause the same problem?

 

It may be noise related if the fan motor is putting a load of s**t on the 12V rail. It may just be worth trying a large value electrolytic, 4700uF 16V, and a 0.1uF disc capacitor across the thermal switch control board as close to the supply as possible. It may help, it'll cost next to nothing and I think it's worth a try before any major mods.

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@ Psy....

 

the Thermal Switch is adjustable...I can turn the fans on/off anywhere from 100f to 260f....thats not the issue....the issue is the relay stutter that fries the contacts over time...this causes the relay to stick on...or not come on at all...

 

 

@ Paul...yes this will fix the issue...

 

I have a light on the fan wire mounted on the dash...with the fan unhooked the light instantly comes on with no load on the relay...but with the fan hooked up the relay can stutter turning the fan on...mostly at idle sitting still as my engine is designed with an under drive pulley to turn the alternator slower than a normal V8....this is to reduce the load on the 6-cylinder engines...

 

it stutters more the more accessories I have on...with the AC on and on max with the fan on high it will do it off idle too...its voltage sensitive...if I unplug the fan and watch the Thermal Switch turn on the trigger wire and then count to 2...and plug the fan it...the fan starts with no stutter...

 

its like the probe is right at the limit where where it almost trips on or off but cant make up its mind....its not temperature sensitive and I played with the temp adjust 20 degrees and its got the same issue...

 

if I could hold the voltage a constant 14.2volts with all accessories on and at idle it wouldnt do it....but the voltage drops at idle because the alternator is turning slower than other engines and this cannot be changed...

 

now I will say this....with the engine OFF and the key on and only running on the batteries voltage of 12.9volts the relay/switch stutters turning the fan On and Off....not just on like whent he engine is running with all accessories on....

 

Make sense...

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I am not sure how to get a 2sec delay in it.

Only thing I could possibly think of would be to put a toggle switch inline. When it hits the temperature flip the switch off for 2 sec. then toggle it back up.

This would be a pain in the butt though.. I will ask around I have some buddy's who are super good with wiring. maybe they will know how to delay the current.

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