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Solid State Relay to control a "Lift" pump

Off Topic Discussion

If it's not really about tuning or wiring. Then it belongs in here.

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Ok this what I have ... 1 x Hella Solid State Relay with pins connected as follows: "87" = Fuel Pump  "86" = ECU aux2   "85" = n/c   "30" = switched 12v   ... the Fuel Pump is earthed to the chassis.

Problem is, as soon as the key is turned on the pump runs ... I want it run only if rpm is 500rpm or higher ... 2 reasons, 1 safety and 2 it is only a "lift" pump supplying a Surge Tank.

I am picking I have the relay pins connected incorrectly but can't find any info that works .... any ideas ???

This is how I have aux 2 configured.

Attached Files

Hi Lostsoul,

With SSR's you need to double check how they are wired, I've attached a few different ways and from the look of things there is a requirement for a diode added to the system and permanent earth on one pin, I think this is because there is so little current needed to switch the relay.

I have a few of the Hella relays to test this out but haven't had the chance as yet

Attached Files

Thanks for that, if a diode is required, my understanding is that it should be placed on the pump side of the relay between the +ve and -ve wires ... ??

to hijack this thread slightly,

i emailed the attached to haltech and they said it will be fine.

my question is when do you or don't you need a fly back diode?

its strange haltech don't need a diode.

what is a good diode to use as a flyback?

Attached Files

I use the Hella solid state relay on my installs. Problem is, as soon you turn the ignition of the, ecu connects to ground and the pump start to run. I us a second conventional relay to open the connection between ECU and SSR.

This thread just brought mo to the idea to connect a pullup or a diode like Haltech does. That should stop the SSR switch when ignition is of.

Do you guys think that this is going to work?

I use a SSR to PWM my cooling fan via my ViPeC V88. I fried two relays in the past. Once due to not using a flyback diode, and the second time due to not wiring it correctly. But I believe that the diode Chris refers to above is not a flyback diode, which is on the hi-power side, but to do with the low voltage control signal.

what diode should i use on the hi power side?

driving a fuel pump so is a 1N4004 ok?

im wiring it how haltech recommends except adding a fly back diode on the high current side and hopefully that works.

I bought my relay from this company and they recommended a relay for my cooling fan, though I do not recall the size.

Sorry to hijack also, but..

why would you need one on the Hi-Power side voltage spike?? do factory cars with variable fuel pumps have these diodes stock? are they a physical module like a relay you have to wire in? or on the PCB of the ECU?

i have 3 narva's hooked up in succession to 3 fuel pumps hooked up and working through the haltech fine, does the haltech have a flydiode built into it?

@ topicstarter : i would use a pullup resitor like 10K ohm so your digital state stays 'high' when unpowered.

@ the others : questions are a bit vague but a flyback is used when closing/interupting something like a coil. wich creates an induction peak. easy checkable with an oscilloscope.