Help troubleshooting turn signal flasher unit

89 245. 130k, dealer maintained and very clean (including all grounds
and fuses I have checked). The flasher unit began ticking erraticaly
without firing any lights a week ago. It quickly progressed to an even
speed of about double it's normal blinker rate. I have replaced the
flasher, most bulbs on the car and cleaned up a bunch of grounds and
fuses, (even though none of them seemed to need any cleaning) and the
flasher has gone back to erratic misfiring. I want to approach this
more scientifically. I picked up a "Bentley" service manual and have
been studying the wiring diagram. What I can't seem to figure from the
wiring diagram is what voltages shoud be present at what points in the
circuit.

What is the cheapest electrical test meter that I can get to be able
to hunt down this problem?

More im importantly what should I test for at the flasher? There are
three connections labeled "31", 49a", and "49" on the wiring diagram
and on my flasher. "31" seems to be a ground. The other two I am not
sure what I should be lookin for there. I want to know what reading I
should get at each of these three connections when the hazards and
blinkers are not engaged. Then I may be able to follow the source of
the error on down the line. I assume that a voltage is being applied
to the flasher when there should be none causing it to fire.

Am I correct in thinking if there was a short to ground somewhere
fuses would be burning out or something worse?

In addition, the bulb out warning light has been acticg up and
sometimes the rear window defroster is triggered by pressing the
brake.

Please help because I love this car and really want to iron these
things out.

Danny

 

Danny

Terminal 30 on the flasher unit, is 0 volts (ground), terminal 15 is fed
battery voltage via the hazard light switch, from fuse 13 when the switch is
released, and fuse 9 when the switch is on, terminal 49a of the flasher is
what goes to the bulbs, the flasher starts when it senses that there is a
return path to ground through a bulb, (do not directly ground 49a, you'll
fry the relay), and obviously 49a then goes live (battery voltage), switches
off, goes live, switches off, ...... The indicator bulbs are connected to
terminal 49a via the indicator switch.
The seatbelt warning lamps are usually driven by the same relay, but the
bulbs are controlled by switches in the seats and belt receptacles.
Before you start ripping stuff apart and probing around with a multimeter,
try changing/testing/servicing the hazard light switch, a bad connection
here would provide a bad power supply to the flasher relay, possibly causing
false firing, also spin the above mentioned fuses in their receptacles to
clean the contact surfaces.

The bulb warning lamp issue has been well addressed by other posters, but
can be caused by using mismatched bulbs, or possibly in your case the fact
that as you mention, the defogger lamp activating with the brake; other
posters and I have to agree, have suggested checking the wiring loom where
it crosses through the tailgate hinge from the body to the tailgate, this is
a bad failure point, wires bend, break, insulation fails, wires touch, check
it to eliminate it, otherwise you'll keep being referred back to it.

Good luck, Ken

 

Thanks a million Ken

I have checked ALL the things suggested in other posts. I have checked
cleaned and spun all fuses and their seats. I have checked the wiring
as it passes into the tailgate and it seems immaculate. I have
replaced bulbs in pairs , cleaned receptacles and cleaned ground
connections.

From my understanding of your answer, the flasher is always being fed
live voltage, and it clicks only when it senses a path to ground
through a bulb. Since all bulbs, including seat belt warning, are
working, and none of them light in accordance with the flasher "ghost"
clicking, it seems that there must be a leak to ground. But you say
that grounding terminal 49a will fry the flasher so I am still
mystified. I have replaced the flasher itself to no avail. Is there
any way of testing the hazard switch or should I just replace it? I
don't think it is faulty, I think it's a sneaky little glith in the
wiring but I don't know how to scientifically discover it?

Danny

 

Check the tailgate harness where they go through the hinges for broken wires
also check the hinges for a broken ground wire some hinges have a ground
wire but my guess is the tailgate harness going through the hinges
Glenn

--
"*-344-*Never Forgotten"
Is for the New York City Firemen who lost their lives on September 11,2001.
The official count is 343, but there was also a volunteer who lost his life
aiding in the initial rescue efforts. And I will never forget them as long
as I live,
nor should any American.
"Mow Green"

 

With the ignition on, the flasher relay is fed a positive supply from the
hazard light sw, with the ignition off, the relay is only fed a supply when
the hazard light switch is activated, since you've changed the flasher, that
should have eliminated it being faulty, if you don't get a flashing seat
belt warning at the same same time as the 'ghost' clicks then it sort of
eliminates the seat belt warning system, directly earthing 49a probably
wouldn't fry the relay but it would blow a fuse.
You can eliminate (or prove) the hazard switch by temporarily bridging the
white and green wire attached to terminal 30 of the hazard sw to the white
wire attached to terminal 49 of the hazard sw, use those clip on wire
connectors, this will by-pass the switch, the hazard lights will still work,
as will the flashers, but the extraneous ticking may just stop, do not leave
this 'bridge' permanently attached, a study of your wiring diagram should
show you that the flasher relay now has a permanent supply from fuse 9, it
won't cause any harm, but, it's not how it's meant to be.
I'm still worried about your mention of the rear screen demister switch
illuminating when you press the brake, this indicates a definite leak of
supply from the brake lamp wires into the demister supply wires, there is NO
other way that the lamp could otherwise illuminate in this scenario, and
unless the wiring has been tampered with, the loom going to the tailgate is
suspect, no matter how immaculate it looks.

Hope this helps and isn't too complex,

Ken

 

Ken, thanks again for your attention. I replaced the hazard switch
yesterday with no improvement, although over the last few days the
'ghost' clicks have become less frequent. I am enjoying sorting this
out and it seems to me, based on my deepening understanding of how
this system works that there must be an intermittent, high resistance,
leak to ground between the output of the flasher unit terminal 49a and
ground. Does that sound right? If so, maybe the best course of action
is to disconnect sections of wiring and replace with new wiring from
that point (terminal 49a) forward until I have removed and replaced
the leaky bit. What do you think?

As to the rear demister, everything looks immaculate at the hinges but
I will begin to dig deeper. Otherwise, things are not so immaculate
back there. The original owner had trailer lights installed and I can
see it is incorrect (wired so as to guarantee bulb failure warning
circuit will fire) and sloppy. I have disconnected it for the time
being and will rewire properly in the future. Furthermore, my Bentleys
manual, owners manual, and fuse panel cover all agree that the left
and right parking lifgts are to be fed off two different fuses (15 &
16). Mine is not only fed off one fuse, but fed through a single
connector to the fuse panel. What I mean is that I cannot simply take
the tang that supplies the left side and move it to the other fuse
because that single tang with two white wires, feeds bothe the left
and right side parking lights.

Thanks again for your help, when this all gets sorted out I will
actually think of you everytime I flick on the blinkers and they turn
off in silence!!!!!

Danny