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This is givin me a freakin headache, whats the deal?

Posted By: StrokerPost

This is givin me a freakin headache, whats the deal? - 08/15/10 04:54 AM

Was rewiring a guys race car, he had no relays and no circuit protection on the fuel pump, water pump or the fan. So I give everything its own relay and circuit breaker, the only thing I did different than I've always done is instead of switching the small HOT wire, I wired it to switch the ground off the relay cuz thats what an article I read said was the proper way to do it. The only "common" connection here is the power point on the firewall, the main feed from there to the breaker and then to the relays for the the w/p and fan come off that. The main feed to the fuel pump comes off the batt. Ok, the problem I have is I turn on any one of the toggles for those components, THEY ALL COME ON!! Why is that? Again, the ground off the relays, not the hot wire, run through the toggles and then to a chassis ground. Even if I pull the ground off the toggle that goes to the chassis for 2 of the 3 circuits, EVERYTHING comes on. What gives? Is it not possible to have more than one relay on a car wired in this way? Is it in someway "backfeeding"? I'm at a loss. I used the same brand stuff I always use, just wired it a bit diff. I wanted to get some input before I went and ripped out several hours of work to wire it the way I normally do it.
Thanks,
Ken.
Posted By: StrokerPost

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:09 AM

BTW, this is the diagram I'm working from, its wired just this way.
Posted By: Dunnuck Racing

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:19 AM

My guess is they are all grounding through the mounting brackets.Try leaving them loose and see if they work,if they do,just mount them to a plastic panel.
Posted By: StrokerPost

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:26 AM

Quote:

My guess is they are all grounding through the mounting brackets.Try leaving them loose and see if they work,if they do,just mount them to a plastic panel.



You mean the toggles? I used lighted toggles that have plastic bodies. The 30A relays are also plastic bodied.
Posted By: Dunnuck Racing

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:31 AM

I was thinking the relays.I have bought some before that had a plastic body,with a small metal mounting bracket.If you mounted them to metal they would ground through the bracket.
I just assumed that is what you were using.
Posted By: Twostick

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:40 AM

That is the correct way to wire them and you can have more than one because my highway tractor has about 20 circuits wired like that. The relays run on switched ground. The only difference I see tho is the primary side of the relays on mine get their power from a separate circuit on its own 5a breaker. Don't know if that matters or not. I think whatever it is it will be ground related. When you step on the brakes and the dash lights come on it usually means the brake lights lost their ground and draw back thru the tail lights which will light up the dash.

Kevin
Posted By: Bob_Coomer

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:56 AM

is it possible that the relays are wired to a normally closed circuit, which powered they would be then open or "off"?
Other than that just use your volt meter and check continuity between the ground and the relay too check to see if its already grounded?
Posted By: HEMIFRED

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 07:05 AM

a race car should only have one relay on the fuel pump. with relays too many wires too many things to go wrong. a good switch, correct wire size and a fuse are all you need
Posted By: StrokerPost

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 07:06 AM

Quote:

is it possible that the relays are wired to a normally closed circuit, which powered they would be then open or "off"?
Other than that just use your volt meter and check continuity between the ground and the relay too check to see if its already grounded?


DING, DING, DING, DING...... I think we have a winner. Just for grins I went back out and simply reversed the positions of the wires on each toggle and now everything SEEMS to be working normally. I still cannot wrap my head around why, but, for now its working. The only "problem" is that with no power lead going to the switches, the lighted switches...arent. Didnt think about that, so, its either leave it like it is, or rewire it the way I used to do it and have the lighted switches. Oh well, thanks guys for throwing some brain cells at this.
Ken.
Posted By: Quicksilver440

Re: This is givin me a freakin headache, whats the deal? - 08/15/10 05:03 PM

Quote:

is it possible that the relays are wired to a normally closed circuit, which powered they would be then open or "off"?
Other than that just use your volt meter and check continuity between the ground and the relay too check to see if its already grounded?



Can he replace the relays with ones that are normally open "off"? And everything would work correctly? Maybe I don't understand his setup....
Posted By: jamesc

Re: This is givin me a freakin headache, whats the deal? - 08/16/10 12:41 AM

without seeing an exact schematic of what you had i can't say for certain but i would be very suspect it is/was the lighted switches and the way you had it wired causing the problem. if one side of the lamp is grounded and the other side connected to the relay (the terminal you're grounding) the lamp will often pull enough to energize the relay coil and turn it on.
Posted By: Leon441

Re: This is givin me a freakin headache, whats the deal? - 08/16/10 01:50 AM

Without seeing a schematic of the lighted switches can't say for absolute sure. But, I will bet the problem is in the switch panel. Just take the wire off the switch and ground it. This way there is nothing to backfeed. If 12 volts from the light portion of the switch goes to the coil on the relay you meant to ground to activate you now have 12v on each side of the coil. No potential difference, I MEAN VOLTAGE.

Leon
Posted By: Thor500

Re: This is givin me a freakin headache, whats the deal? - 08/16/10 02:58 AM

Quote:

a race car should only have one relay on the fuel pump. with relays too many wires too many things to go wrong. a good switch, correct wire size and a fuse are all you need


I agree
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