1996 Miata Excalibur Fuse Blowing

Hi everyone!

I'm installing an Excalibur 1860 in my Miata and I have an issue.

I converted a negative output(Channel 3) to positive through a relay in order to trigger my pop-up headlights(raising and lowering, not illuminated). It works fine.....once, then the 10a fuse in my fuse box blows.

Is this a problem with tapping into a 12v constant source that doesn't have a high enough amp fuse? Is it a problem with my relay not having a diode? If it's the lack of diode, which pins and direction should the diode be between?

My relay is set as follows:

pin 85: (-) trigger from alarm
pin 86: (+) 12v constant
pin 30: (+) 12v constant
pin 87: (+) pop-up headlight output

Thanks for your time and help!

You will need a 5 pin relay, wire thus:-
Cut the headlight motor wire you joined to.
87a to car side.
30 to headlight side.
87 and 86 joined and connected to battery via a 15 or 20 amp fuse.
85 from alarm input.
Diode, 1N4004 across 85 and 86, band to 86 to protect your alarm.
The reason , that headlight motor wire is sitting on ground at rest, you need to separate the motor up wire from its ground source.
This is exactly how a window motor, door lock, or trunk release is done.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thank you very much for your thorough reply!

Question: So the constant 12v needs to be a direct shot to the battery? No taping into existing 12v constant lines under the dash? Miata has the battery in the trunk so it makes it a little more challenging.

look at the fuse box, there should be one large gauge wire thats constant 12v.

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Ted
2nd Year Tier 1 Medical School
Still installing as a hobby...pays for groceries
Compustar Expert

X 2 with Ted.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks.

Is it OK to tap into any other 12v constant under the dash or is it preferable to get it from before the fuse box? It's extremely tight near the fuse box.

The thicker the wire the better, also spreads the load. Isn't there an engine bay fusebox with a constant feed?

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Hi again!

I have a couple more questions that I could use some help with...

1. My Miata has a door trigger wire(-) and a trunk trigger wire (-). Can these be combined and connected to the Door Trigger(-) input of my alarm?

2. My alarm has the following to trigger the dome/supervision light:

Light Relay N/O (+/-) Input BLACK/ Red
Light Relay N/C (+/-) Input WHITE/ Red
Light Relay COM Output GREEN/ Violet

My Miata has a RED / white wire for Dome Light supervision.

How should that be connected?

1) Yes but diode separate, 1N4004, bands towards switches.
2) Not sure, BLACK/ red to ground, GREEN/ violet to door trigger AFTER above diode connection.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Question:

My alarm has a "4 Pin Door Lock Port". One of the wires is a constant 12v output. Can I just tap into this to power my headlight relay?

Thanks!

No it's probably fixed time at 0.8 seconds. If you can set it to 3.5 seconds you're in with a chance, if so give me the wire colours and functions.
Although with 4 pins I very much doubt it, you'd need 6 wires to have internal relays and do this function.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Isn't there a separate headlight switch on that model, bet it's a momentary NEG at the switch to control it, TEST.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

I just looked at the install manual, lock outputs are low current NEG.
Check the headlight lift switch if you have one, above the radio slot (years since I've done a Mk. l)
Test if it's a POS or NEG output from the switch when you press it.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

it wouldn't be wise to pull power from the 4pin lock plug, to power your headlight relay. Use a 12v source that's of capable current load.

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Ted
2nd Year Tier 1 Medical School
Still installing as a hobby...pays for groceries
Compustar Expert

I think the switch is low current but our OP must test, I also THINK it's momentary and logically it would be NEG but again, it's 11:30pm where I am and at leas 3000 miles away so our OP has to again, TEST.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Headlights should be on their own circuit (for obvious safety reasons).
And at least their power fuse should be self-resetting circuit breakers (ditto) except if individually or separately fused.

Note that I'm speaking generally for headlight circuit fusing - not separate or additional headlight controls.

We're talking about the motors that raise the headlights Peter.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Cool. I just dropped in and just saw something about tapping "headlights" to door lock or something.

Of course if raisers require +12V to stay up, my reply is still valid.

Thanks for the replies everyone. I took a little break for the weekend but I'm back at it...

I hope I answer correctly:

There are effectively 3 headlight switches in the '94-'97 Miata/Eunos.

1. The rotary switch in the end of the turn signal stalk that pops the headlights and illuminates them.

2. A momentary switch of some sort is also inside of the turn signal stalk for when you pull it towards you to trigger "flash to pass". This raises the headlight and flashes the lights. The headlights stay raised for as long as you hold back the stalk, then they retract about a second after you let go. This is the line I am tapped into for my alarm. This is where the factory alarm was tapped into for this feature as well.

3. There is a button on the center of the dash that raises the headlights and keeps them up(but not illuminated). This is mainly used to wash the headlights without having the lights on. This is a NEG switch.

Question:

How does tapping into the constant 12v at the ignition harness sound? It's certainly capable of the handling the current and it's wonderfully close to where I want to mount my relays. It's quite tight under the dash.

Thanks again!

I'll also add that I am only interested in popping them for that short period of time that the "flash to pass" offers so the shorter the trigger time, the better. The .08 is perfect.

It works fine as I tested it(except for the blowing of the fuse), I wired up the 5-pin relay like Howie said to prevent that. Now it's just a matter of finding a solid and easily tappable constant 12v source for that relay. Think I'm tapping into the ignition constant 12v as I said. It' around 14ga wire so current-wise it should be solid, right?

Thanks!

Yes provided you aren't running the remote start at the same time.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Well, I have been plugging along and I am almost finished except for one thing...

I installed a truck release solenoid. The standard cheap one that you see everywhere. Problem is, my alarm will not trigger it. I have tested it to be working.

The RED / white wire from my alarm is for "Trunk Release/2nd Channel (250mA -) Output.

I installed a relay, most likely incorrectly, as follows:

30 & 86 - Joined and connected to battery with 30 amp fuse.
85 - RED / white wire from alarm - output
87 - To solenoid

The other prong from the solenoid is grounded to chassis.

Thanks again!

You're wiring is correct, test.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Damn it.

Well with any luck it's just a bad relay. I'll check it again tonight.

You have to hold the button for about 3 seconds before the trunk pops. It's not like the door locks.

Worst case scenario, no quenching diode on the relay, 1N4004 across 85 and 86, band to 86 and you might have fried the alarm outputs.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

So for some reason it was blowing the fuse with the relay connected:

30 & 86 - Joined and connected to battery with 30 amp fuse.
85 - RED / white wire from alarm - output
87 - To solenoid
The other prong from the solenoid is grounded to chassis.

I changed it to:

87 & 85 - Joined and connected to battery with 30 amp fuse.
86 - RED / white wire from alarm - output
30 - To solenoid
The other prong from the solenoid is grounded to chassis.

It works fine now. Any explanation for this?

No except faulty relay? According to ISO
85 = coil -
86 = coil +
87 = power output
30=power input
Except nearly every one wires them the way you did the second time

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Hmm, is it a problem the way I have it running right now since it's working?

Not at all when only using 4 pins of 5 or a 4 pin relay unless it has a built in quenching diode (will show a flow picture on its side), 30 and 87 are interchangeable, = each side, input and output of a switch.
Placing a switch, such as a small push button, one side to ground, the other to 85 will also make an internal trunk release.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

I seriously must me cursed...

I thought everything was fine. Go out to my car this morning and the battery is dead. The trunk actuator seems to be the source of the draw. But why????

Again. This is how my trunk actuator

87 & 85 - Joined and connected to battery with 30 amp fuse.
86 - RED / white wire from alarm - output
30 - To solenoid
The other prong from the solenoid is grounded to chassis.

Good grief.

What makes you think it's the solenoid or relay?
And 15 amps should have been adequate.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.