This morning I used my '78 242 to take our Daughter down to the School Bus Stop. As I was backing in to park I noticed the Brake Lights were not working. All other lights were fine. After the Bus left I started the Volvo and drove home. Later, when it was lighter outside I checked the fuses. Fuse number 9 was blown. Replaced the fuse and tried to start the Volvo...cranked but would not fire, and no lights,(idiot lights) working on the dash panel. Checked again, and #9 blown again. This time left the fuse box cover off after replacing the fuse. As soon as the key went into the ignition slot the fuse blew. Blew even before turning the key??? Take out key and fuse is ok until key is inserted. Tried again and the same result. My rear light panels are old and need replaced, but I can't fine any bare or loose wires. Any ideas? I'm not much of a wrench, but in 50 years of driving have never encountered anything like this. Any thoughts would be appreciated, and Thanks!, Mike.

 

thats a sure sign of a short circuit somewhere between that fuse and wherever it goes. probably somewhere in the middle, the insulation has cracked off, or been worn through, and the wire is touching the car chassis.

according to the 77/78 240 series greenbook, fuse 9 goes to the 'daytime running lights' (flips to page 11,12...). lets see, from the fuse panel, its a white+red wire that goes to the headlight switch pin 15. when the light switch is OFF, pin 5 powers a Green wire to the bulb failure sensor module pin 5, and in turn two Green-Red wires come off pins 3 and 4 on the failure sensor and head for the front of the car where they connect to two brown wires that go to the daytime running lights, which are little bulbs in the front headlight buckets. SOO... somewhere in that wiring you likely have a short.

when the main light switch is off, fuse 9 also powers light switch pin 58 which has a white wire to fuse 11 and 12, and powers the parking, side marker (if any) and tail lights through a whole PILE of wires. license plate lights, too.

when the light switch is NOT off (eg, its in parking OR headlights) then pin 58 gets powered from light switch pin 30 which is wired to the main positive terminal (always)

so... if you turn your headlights on before turning on the key, does this fuse 9 still blow immediately? if so, the problem is likely in the wiring to the front DRL's.

 

Thanks Pierce. Please remenber I'm a simple man. On the fuse box door it says 9 is for the running lights, but the owners manual says seat belt indicator, and ignition. Even with the fuse out the headlights and side marker lights still come on with the light switch. There is a red wire, (aftermarket), near the battery,with a ten amp prong fuse that is blown. It looks to be for a pair of behind the grille lights the PO installed, but have never worked for me. Could it be a short in the rear lights as they are blinking on and off, and are duct taped down? I'll search some more before having it towed to a shop, (ouch!!) Mike.

 

the "running lights" that fuse 9 powers are a separate small bulb thats stuck into the back side (top? bottom?) of the headlight reflector bucket, and causes the bucket to light up whenever the car is switched on.


lights that blink on and off without blowing fuses aren't shorts, they are intermittent circuits. thats probably unrelated to this fuse 9 thing.

 

I replaced the parking light lenses the other day, so that may be it. I don't think I've ever seen the reflector buckets light up when the car starts on any of the 240's I've owned. Are the bulbs under the lenses, or behind the bucket? I'll go out and look, but I won't know anything until tomorrow when I can buy more fuses. In looking for the problem I've gone through three boxes. I'll let you know, and I really appreciate your help, Mike.

 

I've never had a 240 that old (ours is a 87) but on other european vehicles of that vintage (and my 1996 BMW motorcycle), its a little bayonet bulb, smaller than the typical taillight bulb, that's stuck through a hole in the reflector along side the main headlamp. according to the greenbook wiring diagram, on an 78 242, ....

... WAIT a minute. ...

US Model 240's of that vintage had a single round sealed beam headlight, didn't they? this DRL circuit probably isn't even hooked up. look for a green-red wire along each fender that goes to a small connector just behind the headlight....

hmm, or maybe its in the top half of the corner turn signal? the circuit placement diagram is pretty vague.

 

Pierce, there is a green and red wire on the pass side by the headlight, but the two wires are bare at the ends and not connected to anything, nor can I see where they ever were hooked up. There is a black wire loose also, and a blue ( I think) wire that has some bare spots in the insulation. I taped them up, but still blows fuse 9, I found an extra in the jockey box. When the fuse blows there is a noticable spark, and pop. I'll keep looking in the morning. Thanks so much for your assistance, Mike.

 

ok, a fuse that goes pop-spark! definitely means a direct short to ground somewhere on that circuit...

black wires are /usually/ but not always ground.

the fairly thick blue wires to the two headlight sockets are your low beams.

 

have the same ride and will take a peak at those wires...green and red by passenger front lights?

 

according to the greenbook TP-12504/1, 77 and 78 240 DRL's are different.

the 77 didn't run the 'daytime running lights' through the bulb failure sensor, the 78 did. the 77 has brown wires from pin 5 of the headlight switch directly to the DRL bulbs. the 77 drawing shows a inline connector on these brown wires just behind the headlight/cornerlights on each side, and the wires running straight back along the fenders to the firewall, and towards the left-center of the firewall where they go through to the dash.

these wires are only powered when the headlight switch is in '0' (OFF), and the ignition key is in II or III.

on the 78, headlight switch pin 5 goes to the bulb failure beercan. green-red wires go from the beercan through the firewall along each fender to the headlights, and there's an inline connector on each side somewhere just behind the headlight, with a brown wire forward of that to the actual light.

neither diagram makes it clear if the DRL bulbs are in the corner lights or in the main headlights. as I previously said, EURO lights from that generation frequently had a bulb in front of the headligth stuck into the reflector assembly, but US sealed beams deleted this.

these are NOT the same as current DRLs which usually use the headlight low beam..

 

I took some pics
green and red to headlight and there is a black one grounded to the fender behind the windshield bug squirter motor thing...you got a bout 4 grounded wires there...

 

Well, thanks to you two, I followed all the wires, and taped some bare spots. The PO had installed small behind the Grille lights, and as they didn't work, I removed most of the wires, and taped the rest. Installed a new fuse, and she fired right up. I am in your debt. Pierce, I found a small hole in the back of each headlamp housing, as you noted, where I'm sure a tiny light bulb would have gone, although no indication of there having been one installed. Analogies, thanks for the photos. It looks like our 242's are the same color. I'm getting ready for ipd, and although mine is mostly original paint, its time for a respray. I hate the color, and am wanting to go to a dark green. I know I'm in for more work, and will have to leave the engine bay the rust color. I'm also having the interior redone. I know a color change hurts value, but on a car this old does it really matter? Both your opinions would be appreciated. Also, let me know if either of you is coming out to ipd in May. I owe you guys!! Take care, and thanks for being there, Mike.

 

per the greenbook,

on the headlights, the red wire is the high beam, and the blue wire is the low beam, those are 1.5mm wires. all the other light wires are 0.75mm

the front parking lights are white on the left and green on the right side.
the front turn signals are green on the left and blue on the right.

 

I would love to go to IPD but I am way out in California.

my 242 is painted dark blue or midnight blue and it does give it a euro look...I do like the green color very much....

 

IPD is in Oregon. Next state up the coast, heh.

yeah, California is a big place. hah, its 700 miles and 11 hours drive for me.

Santa Cruz, CA to 11744 NE Ainsworth Cir, Portland, OR 97220 - Google Maps

 

For some reason I was thinking of Washington....well 750 miles 15 hours for me.