Ok, this is a little goofy.....

J

joeychgo

Guest
My Mark normally has the headlights on at all times...

A WEEK AGO, I got in and immediately got a message warning to check exterior lamps --- and they were both unlit. However, when I actually turned the switch - they lit fine, same with the brites. But they dont come on unless I turn the switch.

Then, a day later, they came back on again all by themselves...No idea why.

Now they are back off again..... Again, no reason I can notice.

HELP!!!!!!
 
RE: Ok, this is a little goofy.....

Assumption number one - you have Daytime Running Lamps(DRL). Assumption number two - it is a malfunction in the DRL.

My '93 EVTM has the following troubleshooting tips for 'Daytime Running Lamps(Canadian Vehicles Only)':

1. Blown Fuse
2. Open Ground Connection
3. No reduced voltage input to DRL module
---Check Fuses
---Check ground connections
---Check 57(BK) wire for an open
---Check HEADLAMPS fuse by operating 'flash-to-pass' function in the multi-function switch
---Check Horn/DRL fuse, DRL resistor and 932(GY/W)wire for opens
---Check Park Brake Switch and 512(T/LG) wire for a short to ground

Now we'll assume all the fuses are good. BTW, check the fuses in question with another fuse - blown fuses has been known to blow and test good with a test light or ohm meter! Yes that's true.

That leaves basically ground connection(s), DRL resistor or wiring and Park Brake switch or associated wiring.

Since it seems to be intermittent, one could rule out a bad DRL resistor(however circuit 932 wire(GY/W) could be intermittently open).

The ground point in question for the DRL circuit is G301. That is located on the "RH side of floor pan, front of RH front door". Bad grounds may cause intermittent functioning of circuits. This ground may be in question if any reason for dampness and subsequent corrosion(i.e. cabin leak or history of bad heater core).

IMHO the most likely culprit was previously mentioned, the Park Brake Switch. Do you normally use the Park Brake? The switch is closed to ground with the park brake applied grounding circuit 512 to the DRL module through pin number 1 on connector C229. This disables the lights. Either disconnect the park brake switch and test the DRL function or check circuit 512 for a ground with an ohm meter. This could be an intermittent short to ground as well.
 
RE: Ok, this is a little goofy.....

I've checked EVERY fuse but only by pulling them out and looking at them. Ive double checked the parking brake. Can you be more specific as to how to find that ground you mentioned?
 
RE: Ok, this is a little goofy.....

Short of tearing my car apart and taking digital pics, the next best
thing is to post diagrams from my EVTM. I looked for better pics in
the service manual to no avail.

OK, that being said, first the ground(G301):

http://home.earthlink.net/~japeters01/_uimages/G301.jpg
This looks to be low on the passenger side door pillar or perhaps the
door sill. If on the door pillar, ir would be behind the kick panel
(or carpet) or if on the door sill it would be behing the sill plate.
It will be a black wire(s) with a ring terminal secured to the body
by a hexhead bolt/screw. Usually these ground bolts have a greenish
coating to negate corrosion. Obviously you would be looking for an
open circuit preventing a good ground.

This ground is from circuit 57(BK)(pin 6) on the DRL connector(C229):

http://home.earthlink.net/~japeters01/_uimages/C229.jpg
The DRL resistor is on circuit 932(GY/W)(pin 4) on the DRL connector.
This feeds a reduced voltage to the DRL module from the DRL resistor
which BTW is located way up front behind the grill I believe. Check
this circuit for opens.

Then finally the Park Brake Switch and circuit 512(T/LG)(pin 1) on
the DRL connector. Connector 252 connects to the switch on the park
brake lever assembly:

http://home.earthlink.net/~japeters01/_uimages/C252.jpg
You can disconnect this connector(C252) and isolate the switch for
testing. The switch is closed to ground with the park brake lever
depressed and open(no connection to ground) with the park brake fully
released. Check the operation of the switch and look for a short to
ground on this circuit.

The block diagram for the DRL circuits
http://home.earthlink.net/~japeters01/_uimages/DRLcircuit.jpg
shows the relationship of all the components to the DRL module.

From the manual:

How The Circuit Works

With the Ignition Switch in RUN, the Main Light Switch in OFF or PARK
and the Park Brake released, the Daytime Running Lamps (DRL) Module
illuminates the Lo Beam Headlamps at reduced power.

Power for the Lo Beam Headlamps is provided by the Horn/DRL Fuse.
Current flows through the Horn/DRL Fuse, the DRL Resistor and the DRL
Module to the Headlamps. The DRL Resistor reduces power to the Lo
Beams.

When the Main Light Switch is switched to HEAD, the DRL Module
switches full power to the Lo Beam Headlamps through the Headlamps
Fuse, the Main Light Switch, the Multi-function Switch and the 188
(W/BK) wire.

The DRL Module also controls the Brake Indicator. If the Park Brake
Switch is closed, the DRL Module will turn off the Lo Beam Headlamps
and ground the Brake Indicator.

--------------------------------

Note the last paragraph. Does the Brake Indicator work? If it does, I
would lean towards the DRL resistor circuit. The brake indicator lamp
should be lit whenever the park brake is applied or the ignition
switch is in start position. Be wary however that the switch
could 'bleed' enough to ground to disable the DRL but NOT illuminate
the Brake Indicator lamp.

And finally:

----------------------------

Daytime Running Lamps

Canadian Vehicles Only


The Daytime Running Lamp (DRL) system is designed to turn the low-
beam headlamps of the vehicle ON, when the following conditions are
met:

*The ignition switch is in the RUN position.
*The parking brake is fully released.
*The headlamp system is in the OFF position.

The DRL system incorporates a fuse in the power distribution box, a
relay located on the RH side of the instrument panel behind the glove
compartment and a resistor mounted to the right end of the front
bumper bar. The wiring is connected to the 14401 wiring assembly. The
DRL output cannot be measured using most multi-meters nor can the DRL
be adjusted.

---------------------------

I hope this is of some help.
 
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