Ign light need some thoughts

priobe · #1 (**permalink**) 12-09-2009, 10:10 AM

Hey all,

I was thinking of using a light to indicate when my ignition switch is on.

I would like to have this light on when the key is on but turn off when the motor is running.

I was thinking of using a relay turn on the light then taking a signal from the oil pressure to have the light turn off. I am thinking when the pressure is above 5 psi it will then turn off the relay controling the light.

Is there a easier way of doing this?

Gunner · #2 (**permalink**) 12-09-2009, 10:19 AM

I haven't looked at the wiring diagram for the details, but this is exactly how the IGN light in ERAs works. (Also in most vintage cars of my experience.) Does your EM use a different wiring harness from most Cobras?

EDIT: Unless I'm misreading the ERA wiring diagram, the IGN lamp is wired to the I terminal of the voltage regulator. Nothing else is connected there and the other side of the lamp appears to go to ground. Maybe it is that simple - I don't know offhand what the I terminal of the VR is for.

VintageUpgrades · #3 (**permalink**) 12-09-2009, 10:24 AM

Do you currently have a "charge" light or are you running a one wire alternator?

priobe · #4 (**permalink**) 12-09-2009, 02:04 PM

Well, I actually made my own harness from scratch. I did not like the design of the ERA's or EM's ( nothing personal).

I am not using a charge light. The Alt is a Nippendenso 130 amp alt. with 3 wire plug and main output.

strictlypersonl · #5 (**permalink**) 12-09-2009, 03:56 PM

If you use a standard low oil pressure warning light switch, no relay will be necessary. The light will also double for its original purpose: Low oil pressure warning, which ain't a bad thing.

Maurice Butler · #6 (**permalink**) 12-09-2009, 11:23 PM

Quote:

Originally Posted by priobe

I am not using a charge light. The Alt is a Nippendenso 130 amp alt. with 3 wire plug and main output.

The charge light provides an import function of providing a small amount of power to kick start the alternator when the engine is up to idle speed.

The single wire alternators have this built in and is one of the reason the battery goes flat quicker when not being not used than the alternators with charge light.

PANAVIA · #7 (**permalink**) 12-10-2009, 01:29 AM

Quote:

Originally Posted by priobe

Well, I actually made my own harness from scratch. I did not like the design of the ERA's or EM's ( nothing personal).

I am not using a charge light. The Alt is a Nippendenso 130 amp alt. with 3 wire plug and main output.

Priobe,

I completely understand your thoughts on this -- I am still looking for the perfect harness. --

my mods to my SPF harness make me close to happy. --

you mention a 130A Nippendenso Alt -- care to share a PN >?

Steve

priobe · #8 (**permalink**) 12-10-2009, 06:24 AM

Panavia,

The alt that I am using is from a 1992-96 SC 400. You can pick one up at your local auto zone.

I choose this alt because it is very reliable.

CHANMADD · #9 (**permalink**) 12-10-2009, 09:34 AM

How is the ignition light wired in the Lexus...it has one I know that?

Gunner · #10 (**permalink**) 12-10-2009, 09:39 AM

Quote:

Originally Posted by priobe

Well, I actually made my own harness from scratch. I did not like the design of the ERA's or EM's ( nothing personal).

A lot of work but these are simple cars and doing it yer own damn way counts.

Do you have a connection to the VR I terminal? You might try that to see if it works the way you want. I notice Bob didn't comment on it one way or the other. Adding an oil-pressure warning is certainly worth consideration, but I don't know that I'd make it do double duty. A red alert should remain a red alert and never go off because of a minor electrical issue...

strictlypersonl · #11 (**permalink**) 12-10-2009, 11:27 AM

A low-oil-pressure switch will do exactly what priobe wanted, and give the added function of warning about low oil pressure. I see no downside.

The reason I didn't encourage using the alternator function is that I am not familiar with that particular alternator wiring.

Gunner · #12 (**permalink**) 12-10-2009, 02:47 PM

Quote:

Originally Posted by strictlypersonl

A low-oil-pressure switch will do exactly what priobe wanted, and give the added function of warning about low oil pressure. I see no downside.

The only thing I see as a downside is combining two warnings, one minor, one disastrous, in the same indicator. Others may not see it as a problem.

Quote:

The reason I didn't encourage using the alternator function is that I am not familiar with that particular alternator wiring.

It appears to be a stock ERA wiring setup. Do I have something non-original on 707 or is it just a variant you're not familiar with? What other ways do ERAs have the ignition warning light come on correctly?

strictlypersonl · #13 (**permalink**) 12-10-2009, 04:28 PM

All late ERA 427s have the ignition warning light circuit based on a Ford alternator. I don't have a Lexus wiring diagram handy, so I'd rather stay silent than confirm my ignorance.

Gunner · #14 (**permalink**) 12-10-2009, 05:08 PM

Ah, I see. But a Lexus alternator doesn't preclude using a Ford VR... I guess it would make a difference if he's using something else. Priobe, is your system all in the alternator or are you using a separate VR?