Multifunction (high beam / turn signals) switch keeps failing

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Multifunction (high beam / turn signals) switch keeps failing

January 27, 2015, 02:11:18 AM

I've got an '87 T-bird, non auto dimming. So nearly a year ago the multifunction switch inside the steering column went bad, rendering my headlights unable to turn on. At first a few clicks of the high/low would get them to come on, and then that failed. Long story short, after the one that lasted nearly 30 years went kaput, I've gone through 3 aftermarket switches. Does anyone have any idea if I'm just using a py brand, or if there could be something causing them to fail prematurely?

Multifunction (high beam / turn signals) switch keeps failing

Reply #1 – January 27, 2015, 08:27:27 AM

You need to slave the switch out to reduce the current it sees. Another words slave the headlights and your issue is over

Multifunction (high beam / turn signals) switch keeps failing

Reply #2 – January 28, 2015, 03:40:40 AM

Does your car have lamp out warning system, or not?

Multifunction (high beam / turn signals) switch keeps failing

Reply #3 – January 28, 2015, 10:01:10 AM

New headlight bulbs recently? Every time I see a failed multifunction switch, I pull out the headlamp bulbs and find 85/100 watt bulbs, or blue coated poser bulbs. The system is already running near it's engineering limit for amperage, these push it over and stuff starts to melt. By all means, slave the headlamps and run stock bulbs, they'll be brighter that way without pulling wild amperage through the harness and switches, but keep in mind, that the electircal system in that car doesn't have a lot of overhead for extra draw.

Multifunction (high beam / turn signals) switch keeps failing

Reply #4 – January 29, 2015, 12:56:21 AM

I do have a lamp out warning, and the last time I saw it lit up was after someone backed into my tail light and demolished it. I've since had it replaced by a body shop as they also did some other repair.

The driver side headlamp housing bracket is loose, and it wobbles. It also tends to go through bulbs fairly often, which I assumed was due to the shaking (the bulbs are always shattered), but perhaps it could be related?

Multifunction (high beam / turn signals) switch keeps failing

Reply #5 – January 29, 2015, 01:22:21 AM

Quote from: TOM Renzo;443500

You need to slave the switch out to reduce the current it sees. Another words slave the headlights and your issue is over

Quote from: TheFoeYouKnow;443545

New headlight bulbs recently? Every time I see a failed multifunction switch, I pull out the headlamp bulbs and find 85/100 watt bulbs, or blue coated poser bulbs. The system is already running near it's engineering limit for amperage, these push it over and stuff starts to melt. By all means, slave the headlamps and run stock bulbs, they'll be brighter that way without pulling wild amperage through the harness and switches, but keep in mind, that the electircal system in that car doesn't have a lot of overhead for extra draw.

How do you "slave" the headlights? I'm having this same problem with my Ranger.

Multifunction (high beam / turn signals) switch keeps failing

Reply #6 – January 29, 2015, 04:26:53 AM

To "slave" the headlights is to rewire them such that the stock wiring serves only to activate high current relays which would then power the headlights, providing a more direct, low resistance path for power to the lights. This reduces current through the headlamp switch and multifunction switch, as well as usually having the side effect of brighter stock lighting.

Multifunction (high beam / turn signals) switch keeps failing

Reply #7 – January 29, 2015, 07:26:53 PM

You can do it with two 30A Bosch relays (this is just what I keep on hand in my garage) on the 87-88 cars as well as the 83-86 cars. This is a simple calculation by taking the wattage of the bulb(s) you intend to use and dividing that by the voltage. I would calculate all of this based on 12 volts since it is a 12V system even though the alternator will bump it to 14.5V. The lower voltage will create a higher amperage draw so that is the safer calculation. So for a certain watt (W) bulb in a certain volt (V) system the formula to calculate amperage (I) is as follows:

I = W / V

I believe a stock bulb in an 87-88 car the low beam is 45 watts and the high beam is 65 watts. So for a 87-88 car you will have 90W on low beam and 130W on high beam. This equivalates to 7.5 amps of draw on the low beam and 10.833 amps of draw on high beam.

With the 83-86 cars I am pretty sure that the outside headlight is 40 watts on low beam and 55 watts on high beam and the inner headlight is 50 watts on high beam. So for the four headlight cars this would mean you will have 80W on low beam and 210 watts on high beam. This equivalates to 6.667 amps of draw on the low beam and 17.5 amps of draw on high beam (remember all four headlights are energized with high beam).

Wiring the Relays
To power the relays you would want to run a wire from your battery to #87. I would use a minimum of a 10 gauge wire to each one and fuse it according to the power draw that relay will see. So from the calculations above a 10A fuse on the low beam will work in either case. For the high beam relay you can opt to use a 15A fuse for the 87-88 cars and a 20A fuse on the 83-86 cars. All of this is assuming stock wattage bulbs so do the calculations for your application.

Run a chassis ground (I usually use the same green machine bolts on the top of the core support that ground the stock head light harness) to #85 on the relays.

I would go to the parts store and get the headlight pigtails for your specific application so you are not cutting up the stock wiring harness. They are about $4 for the low beam and high beam both on the 83-86 cars and about $8 for the high/low beam pigtail on the 87-88 cars. From here you can use a male spade crimp connector to plug into the stock headlight harness to get the turn on signal from the low and high beam wires to trigger the relays. You would go from the low beam on your stock harness to #86 on the low beam relay and from the high beam on your stock harness to the #86 on your high beam relay.

To power the low beams on either the 87-88 or the 83-86 cars simply run two 18 gauge wires from #30 on the low beam relay to each low beam bulb connection point.

To power the high beams on an 87-88 car simply run two 18 gauge wires from #30 on the high beam relay to each high beam bulb connection point. To power the high beams on an 83-86 car simply run two 14 gauge wires from #30 on the high beam relay to each inside head light high beam bulb connection point. Jumper from each inside high beam head light over to the outside head light high beam connection point next to it with an 18 gauge wire.

There is not a lot of draw for each low beam bulb (less than 3.5 volts for 83-88 cars) and the voltage drop in 5 feet of 18 gauge with 5 amps of draw at 12 volts is about 0.33 volts. There is a little more draw on the 83-86 cars per side for the high beam bulb (less than 8.25 volts) than the 87-88 cars (less than 5.5 volts) and the voltage drop in 5 feet of 14 gauge with 10 amps of draw at 12 volts is about 0.26 volts.

Do depending on where you mount the two relays you will only use one side of the head light harness to trigger the relays. The amperage required to trigger each relay is around 0.300A so you can run 18 gauge wire from the stock head light harness to the relays. From this you can see how this reduces the loading on the head light switch and keeps the head light switch connector from melting at the head light switch. Hope this picture helps illustrate the wiring references to the relay:

So you can see that at rest (i.e. #86 not energized) #30 and #87a are common. When the relay is working (i.e. #86 is energized) #30 and #87 are common. This is how you are getting the battery 12V+ over to the head lights when the head lights are turned on and selected between high beam and low beam.

Hope this makes sense and helps a few understand how this works. You can buy already built wiring harness with relays to do this but I like building them so I know how to fix them and it only costs me about $15.

Darren

Multifunction (high beam / turn signals) switch keeps failing

Reply #8 – January 29, 2015, 10:00:37 PM

That is a very good post. It needs stickied.

Thanks for writing it up.

Multifunction (high beam / turn signals) switch keeps failing

Reply #9 – January 29, 2015, 10:33:49 PM

I felt like Will Ferrell when he answers the debate question in Old School minus the blacking out part.

Darren

Multifunction (high beam / turn signals) switch keeps failing

Reply #10 – January 30, 2015, 10:17:37 AM

here is the how to choices

Relay adds to remove heat from headlamp and ignition switch
http://www.foxtbirdcougarforums.com/showthread.php?35095-Relay-bank-mod-COMPLETE-for-IGN-switch-Headlamp-and-Marker-lamps

results of my headlamp modification
http://www.foxtbirdcougarforums.com/showthread.php?35224-After-my-headlamp-modification&highlight=

HIGH BEAM *with * low beams on modification ~just an easy jumper wire. ((applicable to those with auto lamps only))
http://www.foxtbirdcougarforums.com/...054#post408054

headlamp rework and remirror the insides, clear coat the outter lense
http://www.foxtbirdcougarforums.com/showthread.php?34549-Re-mirror-headlamp-interior&highlight=

Multifunction (high beam / turn signals) switch keeps failing

Reply #11 – January 30, 2015, 08:55:03 PM

Here is how i do it . This is on a MUSTANG Similar to a TC
No complications simple clean and neat. No need to build a POWER plant relay setup.

Multifunction (high beam / turn signals) switch keeps failing

Reply #12 – January 30, 2015, 09:56:55 PM

Quote from: Aerocoupe;443660

I felt like Will Ferrell when he answers the debate question in Old School minus the blacking out part.

Darren

lol

Multifunction (high beam / turn signals) switch keeps failing

Reply #13 – January 31, 2015, 06:56:12 AM

Ya, this is how it should look like. Other option is to have a high beam relay on a wheel well next to the battery.

My first question, if his car has lamp out warning was quite important, because if it has not, he can use two relays on the wheel well and call it a day. If his car has this system, the relay must be connected prior system's measuring points and therefore it has to be wired inside the cabbin just after the headlamp switch, which means the headlamp switch powers up the relay and all the current goes through the relay and not the switch. The other relay just switches between low and high beams.

Multifunction (high beam / turn signals) switch keeps failing

Reply #14 – January 31, 2015, 08:24:01 AM

Bingo!!!!!!!!!!!!!!!!!!!!