Hi, might be long if your dinner's ready

Polar white auto sedan, 182k;

I've come to expect a peaceful transfer of power from the battery to the engine on this car, but last Saturday evening I was travelling down my lane on an emergency errand for sour cream for our pierogies when a turn of the headlight switch incited a riot on the dashboard.

The left side flickered, then illuminated, followed by a slight pause and then a click after which the alt., brake warning and parking brake lights joined in the fracas. Somewhere in the middle of this the speedo spiked to 30, then fell back and the engine quit.

I think I turned the headlights off, although I'm not certain, but I did turn the key off and then back on to engage the dash lights. I got the same light show, no fuel pump response, yet cranking the starter produced a second or two of running before stalling again. Further cranking had no effect.

My main focus was on a waiting dinner and the general store about to close, so I walked the 200 meters back to my yard and engaged alternate transport. I wished the car a pleasant evening and hopefully a dry night because the power windows were in on the plot.

The following morning I visited the car, but to my disappointment the dash lights came on normally, the fuel pump signalled, and the engine started up as if nothing had happened. I resisted turning on the headlights until the car was back home, but when I did they behaved themselves.

Through the day I started the car several times hoping to confirm that the headlights were triggering the reactions. At a last attempt at about 5 o'clock the bad behavior returned. The headlights did trigger it, but this time it also included a loud buzzing coming from the dash area whenever high or low beams, or the stalk flasher were on.

Suspecting the headlight relay for the buzz, I consulted Bentley who advised it was under the center vents. I tore the center consul apart without locating it. Dinner time again so one more night with the windows open.

The next morning was the same as the last. No buzzing, everything normal. I went ahead and found the relay anyway, up by the brake pedal where the Haynes manual said it would be, and it looked good with no signs of overheating.

I probably should have checked the vehicle grounds earlier, but I did so now and when pulling on the big blue wire hidden under the battery it offered no resistance. It came out completely and cleanly broken off from it's terminal.



The only other circumstantial evidence I have is that both times the fault appeared at end of unusually hot days, and did not appear on much cooler mornings. My questions are - would the broken ground explain the symptoms, and what might I check if the fault returns ?

Peter

Just an anecdote -

One winter night my '90 744TI stalled a couple of times. I then figured out that the car stalled when I turned on the high beams!

Its in the FAQ

I cleaned the ground in the left front fender and all was well.

As for grounds, it is a decent idea to add a couple to your car, especially engine to body.

At the Swedish Car day, Lars Anderson transportation Museum near Boston, I looked at a few souped up SAABs - They all huge ignition wires and grounds, stereo wires as well.

In case you're interested here are similar symptoms for a 960 with a bad battery cable
https://www.brickboard.com/FAQ/700-900/960_90Info.htm#DriveabilityRottenBatteryCables

As much as that article carries on to desribe how to repair or build your own battery cables, I think most of us would suggest going for a new pre-made cable. Battery cables are not created equal when it comes to quality and construction. It's sometimes hard to tell from the pictures. Genuine Volvo cables are well built, but can be expensive and many are no longer available. I'd prefer a good used Volvo one over half the aftermarket stuff I see.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

"Suspecting the headlight relay for the buzz, I consulted Bentley who advised it was under the center vents. I tore the center consul apart without locating it. Dinner time again so one more night with the windows open."

That's where it moved in '91. In '90 it was under your feet.

"...big blue wire hidden under the battery..."

That's the battery cable's chassis ground. Without it, every load on the alternator referenced to the car body needed to return through the radio noise ground strap (firewall to cam cover). The fuel injection returns through engine block grounds (at the fuel rail mounting screws). The battery negative to alternator connection looks like it is OK, assuming you saw no trouble with the battery cable's big lug bolted to the block.

No excuse for 187 minutes of open windows if rain predicted.

PS - I believe any large load grounded at the body would have done the same as your headlights, for instance the heater blower. No indictment of headlights.
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Art Benstein near Baltimore

"Freedom of speech gives you the absolute right to pose any question you like based on whatever unsubstantiated assertion you choose."

Ok Art, my apologies to the headlamps.

With all the commotion on the dash, I don't think I immediately connected activating the lights to the breakdown. It was only later in the evening when reflecting on the incident that I put those things together.

I think it likely that I did not turn the lights off when trying to restart the vehicle, and that it would have run if I'd done so. They were turned off when I returned in the morning but I would have done that instinctively.

There had been a sharp 90 degree bend in that ground cable where it joined it's terminal which may have had something to do with the failure. The cable is not long enough to avoid that bend. There was no sign of corrosion. I noticed on my 91 that the terminal was repositioned kinklessly to the inner fender. It may have been off for quite a while. The blower hasn't been on since April, and the lights not since May when my daughter was visiting and gallivanting around after dark.

I still wonder why the fault wouldn't show up in the mornings. Would a 50 degree rise in temperature change the resistivity of the alternate ground enough to put it over the top ? This car has a braided ground strap from the wiper motor to the strut tower. Is that an add on by a PO ? I don't see it on either my 90 or 91 wagons.

Thanks for the explanation. I feel better for it.
Peter

I stand corrected.

Or did that change at some point, Art? I just looked at my 242 and it's like I said.

As usual, this is all very confusing.
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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Yes, Don, I was puzzled by your response.

Just checking, green book shows battery cable colors in 1980 to be the same as those in 1990: Red is positive and blue is negative.

However, in a pinch, I might use a good blue one found in salvage for the positive side, but I'd sure as hell do something to flag at the battery end.. Yes, I know, they all have red part number labels.
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Art Benstein near Baltimore

"Smedley had become the Clint Eastwood of chicken crises." -Kenn Amdahl

Art, I completely forgot that the positive and negative cables changed sides at some point. Not that that has much to do with this discussion. But it's all coming back to me now.

And the color should have been a dead giveaway. Of course, my '89 had the pigtail off the negative cable. But I was thinking pigtail = hot wire to the junction box.

I think if I had seen the eyelet it would have jogged my memory.

Getting old sucks.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

I stand corrected.
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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

That is not a ground wire. That wire provides power to the junction box on the left side of the engine compartment. If it's broken a lot of stuff won't work. It must have been hanging on by a few of strands of copper wire, hence the weird behavior, and broke completely when you removed it. You wouldn't be able to start the car with it completely broken or disconnected.

Take heart! It's an easy fix.

Edit:

As I read your post again, "...when pulling on the big blue wire hidden under the battery it offered no resistance. It came out completely and cleanly broken off from it's terminal," makes it sound as if this was not connected at all. That sucker is always hot and you don't want it just lounging around like that.

Was there another wire of approximately the same gauge from the + battery terminal to the j-box? Maybe some jack leg fix by a previous owner or mechanic?


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Hi Peter,

You found the troublemaker.
Fix that busted ground before running the car again.

Bill