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Problem with 12v relay

Started by _Chriskoss-79uc_ , Nov 03 2008 12:58 PM

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28 replies to this topic

#1 _Chriskoss-79uc_

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Posted 03 November 2008 - 12:58 PM

Torana wouldn't start this morning

I have electronic ignition and a 12v relay.

The old power wire that used to go to the coil, but goes into the relay has power
But the new 12v wire FROM the Relay TO the coil has no power

Does this mean the relay is out...
All has power but that new wire going to the coil.
Can't see why it wouldnt have power
Even the fuse from the battery to relay has power

Any tips

Thanks

Edited by Chriskoss-79uc, 03 November 2008 - 12:58 PM.

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#2 _The Baron_

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Posted 03 November 2008 - 04:47 PM

Give the relay a flick with your finger or replace it.

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#3 _Chriskoss-79uc_

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Posted 03 November 2008 - 04:57 PM

Thanks Baron..

So it'd be the relay then right..? seeing as everything has power besides the output wire

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#4 _SS Hatchback_

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Posted 03 November 2008 - 09:54 PM

join the wire that comes from the battery to the one going to the coil and if it starts then your relay is gone but going by what you are saying it sounds like the relay is gonne anyway, just remember to disconnect the battery from the coil when your done

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#5 _The Baron_

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Posted 03 November 2008 - 10:12 PM

^^^ What he said.

Has it run with this setup before?

Has the relay contact burnt out due to the contacts not being rated high enough for the coil current?

Got a mate who is electrically savy?

Pity you are not in Adelaide, I could look for you!

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#6 _Chriskoss-79uc_

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Posted 03 November 2008 - 10:52 PM

Yea Baron, been running the relay for a month or 2 now.

Terry (ALX76) has told me relays do blow out, but after 10-20 yrs or so.
Just weird that this one is new.

I've wired the relay up as per diagram, so it should be running fine.

It doesn't matter the thickness of the wires does it mate?. is that what you mean by contact rate (Im totally clueless with electrical stuff)

Cheers

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#7 _SS Hatchback_

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Posted 03 November 2008 - 11:08 PM

Yea Baron, been running the relay for a month or 2 now.

Terry (ALX76) has told me relays do blow out, but after 10-20 yrs or so.
Just weird that this one is new.

I've wired the relay up as per diagram, so it should be running fine.

It doesn't matter the thickness of the wires does it mate?. is that what you mean by contact rate (Im totally clueless with electrical stuff)

Cheers

No what he meant is the amp rating of the contacts of the relay, if your relay is rated at 20amps and your coil draws 25 amps then it will burn out your relay contacts in no time.

The thickness of wires does matter also because you can burn the wires out with to much current , again its like the relay you need to have the correct rated cable for the amount of amps drawn by the item. Hope that helps

Read my other post and test that first, good luck and let us know how you go.

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#8 _Chriskoss-79uc_

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Posted 04 November 2008 - 09:11 AM

Hey SS-hatchback..

I tried what you said.. still won't start.

So I put the test light on the wire from the battery to relay.. it has power before it hits the fuse in the circuit.. this mean the fuse is blown (well obviously)

Thing is, its blown many times now, like 2-3..

Does this mean the rating for the relay is too much, how can I fix this problem?

Cheers

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#9 _The Baron_

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Posted 04 November 2008 - 11:36 AM

Fuse rating?

Any details on the relay?

The common Hella relays are normally good for 30 amps.

Next thing to do is disconnect the coil wire at the coil +ve, replace the fuse (if needed) and switch on the ignition.

Did the relay click? Any power at the coil wire?
YES power= maybe the coil is burnt out and causing a short resulting in the fuse blowing.
NO power=Check power is comming from the battery to the relay.
YES= relay is stuffed
NO=fuses is blown again=check wiring for insulation damage.

It is also critical the wire can handle the fuse capacity selected.

Edited by The Baron, 04 November 2008 - 11:37 AM.

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#10 _Chriskoss-79uc_

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Posted 04 November 2008 - 12:43 PM

Im using pretty thick wire, so it should hold it.

Anyway, I went and bought two new fuses and a new relay.

The old relay was still clicking, it couldn't be stuffed.

I replaced the fuse with 1 of the new ones.. nothing

Then replaced with another new fuse, exact same.. car started

Wierd.. lol

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#11 davelh

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Posted 04 November 2008 - 04:00 PM

What size fuse are you using, it may well be under rated for the application.
Maybe try a slightly larger fuse, depending on what size your wiring is, but say, an increase of 5 amps?

Dave

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#12 _Chriskoss-79uc_

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Posted 04 November 2008 - 04:12 PM

Thats a good idea mate.

On the relay diagram it said to use 20amps so I just use the 20 amps one (yellow fuse)

But if it blows again I may go 25 then

Thankyou all, much appreciated

Edited by Chriskoss-79uc, 04 November 2008 - 04:12 PM.

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#13 _SS Hatchback_

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Posted 04 November 2008 - 04:54 PM

ChrisKoss, good to see you have it starting now. The problem with placing a 25 amp fuse in a 20amp rated relay is that the relay will burn out before the fuse. The idea of the fuse is to be the weakest link in the circuit so if you have a problem rather than burn wiring or relay the fuse will blow. Try to check how much current your coil draws and if it is higher than the rated relay then go a bigger relay and a bigger fuse, ie
If it draws 21 amps then instead of just puting a 25amp fuse in , buy a 30 amp relay and then run a 25 or 30 amp fuse.
You can check the current draw using a decent multimeter , wouldnt cost too much to have auto elect check this for you if your not sure how to do it. Basically just needs to place the meter in series with the wire going to the coil.

What colour was the original fuse you took out? Im assuming its the blade style fuse. Basically just asking what The Baron was suggesting whether it just was a wrong rating fuse and now it has the correct one in.

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#14 _Chriskoss-79uc_

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Posted 04 November 2008 - 05:19 PM

It was yellow, so 20 amp as it says on the fuse itself, and yes its the blade style fuse.

Ill take a pic soon of the fuse holder thing I'm using.
All my gear is just from dick smiths, cheap and nasty crap.

Got alot of holidays now that i've finished year 12, maybe I should get on wiring all this stuff up neatly.

Thanks again all

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#15 _torbirdie_

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Posted 05 November 2008 - 05:17 AM

It was yellow, so 20 amp as it says on the fuse itself, and yes its the blade style fuse.

Ill take a pic soon of the fuse holder thing I'm using.
All my gear is just from dick smiths, cheap and nasty crap.

Got alot of holidays now that i've finished year 12, maybe I should get on wiring all this stuff up neatly.

Thanks again all

Is it just a normal commodore bosch electronic dizzy and coil?
If its blowing a 20A fuse then something is not right.
5-7A should be all that it draws.

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#16 _The Baron_

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Posted 05 November 2008 - 08:20 AM

^^^Yes I agree.

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#17 _Chriskoss-79uc_

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Posted 05 November 2008 - 10:54 AM

Yep, normal Commodore HEI ignition..

It isn't wired up all 'professionally' though.. could that be why.

The fuse has only blown once mind you, so if it happens again I'll know somethings not right

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#18 davelh

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Posted 05 November 2008 - 04:23 PM

Fuses can blow for no reason, vibration is a big killer, so it could be you just got unlucky.
You should also look at how you have wired the relay up, i dont have much knowledge on the HEI coils, but from the sounds of it, 20A may be a bit much.
Also, when dealing with that sort of current, DO NOT put your multimeter in series with the circuit, until you make sure it can handle the current, and that it is fused - you may kill the multimeter or the circuit.
Also, make sure you put the lead back in the correct socket on the meter after checking for current, otherwise next time you check for volts, you will short something out.

Is your coil performing as expected? I would also think that high current draw may be caused by shorted windings in the coil, hence the higher current draw. Perhaps if it happens again, borrow another coil and test that out.

Dave

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#19 _Chriskoss-79uc_

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Posted 05 November 2008 - 04:30 PM

I have several coils, and the ones used in the commodores (non oil type) seem to work better than the oil-filled coil (I have one of those too)

It could also be the module perhaps.

Ahh, 1 of the bad points of having HEI.. alot of things can go wrong

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#20 _Stuart_

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Posted 10 December 2008 - 10:16 PM

^ If done correctly alot less things should go wrong with HEI compared to points. Otherwise why would it be such a good upgrade.

Also I've heard that you should run a 30A cable to the coil, so you need a 30A rated relay/wire/fuse.

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#21 Rockoz

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Posted 10 December 2008 - 10:35 PM

Just a guess on what chris has said so far. Check the actual fuse holder and its contacts and connections. Some of the cheaper ones will over heat at only low current draws. A bit like the problem that VK and VL owners experience with headlight fuses when they up the wattage.

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#22 _torbirdie_

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Posted 11 December 2008 - 09:09 AM

^ If done correctly alot less things should go wrong with HEI compared to points. Otherwise why would it be such a good upgrade.

Well it depends on your application:
There appears to be a lot of problems with some sorting out their power supplies, which is just a once only thing.
Electronic ignition is basically zero maintenance, but that doesnt equate to 100% reliablity. Two components, the reluctor coil and the module can fail basically at any given time, and there is no easy roadside fix.
Points sytems need adjustment every 5000km and possibly will fail beyond 10000km. But once set, they are right to go and wont be the source of any random break downs in the between times.

Also I've heard that you should run a 30A cable to the coil, so you need a 30A rated relay/wire/fuse.

You heard wrong. 15A wire will be fine, current draw is ~7A. Its not going to hurt to use 30A wire though and any relay should be up to the task.

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#23 MRLXSS

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Posted 11 December 2008 - 09:17 AM

I have my 12V to the coil wired up like this

http://www.gmh-toran.......ticle&id=23

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#24 _Stuart_

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Posted 11 December 2008 - 10:50 AM

^^ agree

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#25 _Chriskoss-79uc_

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Posted 11 December 2008 - 11:01 AM

I tried the single wire way a long time ago, but didn't seem to be giving the coil any extra voltage, but I didn't have a test light at the time so there was no way I could tell if it was actually connected properly. Now I do, so I'm going to try the single wire method 1 more time, as the fuse keeps blowing in my relay setup and I can't figure out why.