West Coast Fieros Homepage
Forum Home Forum Home » Technical Topics Forum » Technical Questions and Discussions
  New Posts New Posts RSS Feed - Headlights
  FAQ FAQ  Forum Search   Register Register  Login Login

Headlights

 Post Reply Post Reply
Author
Message
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Topic: Headlights
    Posted: 03 April 2010 at 5:57pm
Hey there. I can find a wiring diagram on this but nothing that shows me the internals (Coils/contacts) of the isolation relay and individual headlight relays. I'm chasing a strange fault.


History:

The 84 I bought had the motors disconnected, so now it's time to get the headlights working again.

Symptoms, first problem:

I found the car with both motors disconnected at the headlight relays.

I plugged in the drivers side motor at the and the motor spun continuously. I changed that motor with a spare I have and that fixed this side.

So the first problem is fixed.

The other motor runs ok when plugged in.

Symptoms, second problem:

So, now the trick is that the headlights will go up, and will sometimes go down. Sometimes when I turn the switch off, the lights hang up, and the lights themselves dim, but do not extinguish. The voltage on the yellow wire (Main output to the headlights) dropped to 8V from 12V with the switch off. I checked the grounds and they are ok. It is definatley a +12 source issue.

I suspected that the switch is faulty (Leaking +12V), so I changed it with another I have. The same fault happened, again intermittently.

So, I figured I have two bad switches. I took one apart and it looked ok, and tested out fine with an ohm meter.

The one wire which I'm not sure of the function of is the white wire. It is +12 from the switch when in the off position, and open circuit (0V) when the headlight switch is on. It goes to the isolation relay. If I jumper this wire to a solid +12, I can't make the headlights screw up. They work great. So what is the white wire for???

Its obviously switched for a reason, but I can't figure it out without more info.

Any insight greatly appreciated.

Thanks,

Chay
86 SE 3.4
Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2010 at 9:10pm
Found it:



The white wire is the headlights close hot lead. It supplies +12 to the motor in the opposite direction to close the doors. I think I'll eliminate the switch contact by jumpering the orange to the white. My rational is that when the switch is off the white wire is +12, and when the switch is on, the white wire is backfed to the switch by the yellow wire, so why did they switch it in the first place? I don't know.

Chay
86 SE 3.4
Back to Top
Dr.Fiero View Drop Down
Senior Post God
Senior Post God
Avatar

Joined: 12 February 2007
Location: Canada
Status: Offline
Points: 1726
Post Options Post Options   Quote Dr.Fiero Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2010 at 9:10pm
I'll try to find my 'good' diagram, but in the mean time...

There's a diode in the isolation relay.  Seen it go bad many times.  Looks like a 1N914 or similar.

Pop the tops on all 3 of them, and file the points.  They're pretty exposed to the weather.

Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 8:59am
If that diode failed short circuit then the relay would hang eh?

I think it's a failed switch though because if the diode failed short it would hang for sure when I jumpered the white to +12

If the diode failed open the doors would never open...so that can't be it.

I'll check it out though.

Chay
86 SE 3.4
Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 9:40am
Thinking a little more, you may be onto something there.

The lights won't come up without the white being powered up. The lights go on and there is an audible click (The iso relay turning on) however.

That would tend to implicate the diode as well, or the contact on the cathode side of the diode.

Thanks again,

Chay


86 SE 3.4
Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 11:15am
Ok, I give up. I have the iso relay out, how do i get the top off without wrecking it?  Does it just pry off?

Thanks,

Chay
86 SE 3.4
Back to Top
Dr.Fiero View Drop Down
Senior Post God
Senior Post God
Avatar

Joined: 12 February 2007
Location: Canada
Status: Offline
Points: 1726
Post Options Post Options   Quote Dr.Fiero Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 1:16pm
There's a couple of small tabs there.  Just get two really thin screwdrivers under the edges and pry out a tiny bit.  It'll drop right out sometimes.  Sometimes you have to tug it out, if they used a lot of the black goop.

Here's a color version of your pic (for anyone else who finds it easier):


Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 5:51pm
Yup, 1N4005 (1A general purpose rectifier) failed to short.

I replaced it and now I'm waiting for some epoxy to harden (I split the case a bit getting it off) and then I'll try it out. I'm cautiously optimistic.

Chay
86 SE 3.4
Back to Top
CFoss View Drop Down
Senior Member
Senior Member
Avatar

Joined: 13 February 2007
Location: Canada
Status: Offline
Points: 580
Post Options Post Options   Quote CFoss Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 6:22pm
Works great! Saaawweeet.


Thanks again,

Chay
86 SE 3.4
Back to Top
Dr.Fiero View Drop Down
Senior Post God
Senior Post God
Avatar

Joined: 12 February 2007
Location: Canada
Status: Offline
Points: 1726
Post Options Post Options   Quote Dr.Fiero Quote  Post ReplyReply Direct Link To This Post Posted: 04 April 2010 at 7:03pm
Great!  Glad it worked for you.  Far from the first one I've seen die - won't be the last.

Had one die (shorted presumably) where the relay got so hot you could barely touch it.  Would kill the persons battery after a day or so of being parked (go figure). 

Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.