Roger Levy

I drove the car today at slow speed, either first or second gear,
flicked on the high beams and it immediately stalled out so the problem
seems to have nothing to do with the overdrive relay. The car is
perfectly normal with headlights, it's only the high beams.

I looked for ground wires and the only one clearly visible was coming
directly off the negative battery post and it was attached to a
structural member near the right front wheel well. Things were a bit
cluttered on the left side and I didn't see any grounding there or near
the firewall which is a typical location on other cars. Do I have to
start removing stuff to see other ground wires?

Any wire I could see, ground or otherwise, appeared to have completely
intact insulation and no corrosion at contacts. There's not even a
trace of corrosion at my battery posts. I know that faulty grounds are
widely believed to be the root cause of many Volvo problems but thinking
a bit analytically it doesn't seem like a bad ground, which implies an
open circuit, could be the cause of this problem, i.e. switch on high
beams, open circuit in the headlight electrical path => car stalls makes
no sense. I could see some sense to a short being involved but I would
expect a fuse to blow in that case.

Any other ideas group?

Roger

don hodgdon wrote:
> "Roger Levy" <rhl@i3e.org> wrote in message
> news:42kWd.69462$8a6.29701@trndny09...
>
>>I'd like to follow up on two concerns cited by James and Michael. I
>>have an 87 740GL sedan with auto, 159K miles, that I've owned 5+ years.
>> It's running very nicely but it has two problems I'd like to fix. 1)
>>The roof liner is sagging in the rear, and 2) last week I flicked on the
>>high beams and the car immediately downshifted! I flicked them on and
>>off a few times and the car downshifted each time then it stalled while
>>traveling at 40 MPH. BTW, the car had an alternator problem several
>>weeks ago which I fixed by replacing the brush/regulator module and the
>>battery was fully charged when the stall occurred.
>>
>>You guys said the liner and wiring harness are tough problems. I'm
>>guessing that the high beam issue indicates a short. Do you have
>>recommendations?
>>
>>Roger
>
>
> I'd say the cheapest and easiest things to check would be the grounds. All
> sorts of strange things can happen on a 70 when the grounds start to fail.
> There are strips near the front of each inner fender where many of the
> underhood grounds are attached. Clean all the contacts and check the
> connectors for corrosion.
>
> You say the car downshifts when you flick the headlights...does the tranny
> actually downshift or is it the overdrive cycling on and off?
>
> Don

Michael Pardee

"Roger Levy" <rhl@i3e.org> wrote in message
news:ak9Xd.92191$g16.33954@trndny08...
>I drove the car today at slow speed, either first or second gear, flicked
>on the high beams and it immediately stalled out so the problem seems to
>have nothing to do with the overdrive relay. The car is perfectly normal
>with headlights, it's only the high beams.
>
> I looked for ground wires and the only one clearly visible was coming
> directly off the negative battery post and it was attached to a structural
> member near the right front wheel well. Things were a bit cluttered on
> the left side and I didn't see any grounding there or near the firewall
> which is a typical location on other cars. Do I have to start removing
> stuff to see other ground wires?
>
> Any wire I could see, ground or otherwise, appeared to have completely
> intact insulation and no corrosion at contacts. There's not even a trace
> of corrosion at my battery posts. I know that faulty grounds are widely
> believed to be the root cause of many Volvo problems but thinking a bit
> analytically it doesn't seem like a bad ground, which implies an open
> circuit, could be the cause of this problem, i.e. switch on high beams,
> open circuit in the headlight electrical path => car stalls makes no
> sense. I could see some sense to a short being involved but I would
> expect a fuse to blow in that case.
>
> Any other ideas group?
>
> Roger
>
That sounds like shorts in the harness, all right. The insulation in areas
where it is protected is usually okay, so the problem is probably going to
be under the hood. A visual inspection of the small wires where they leave
the covering of the bundles may show up something. Try not to disturb them
more than necessary - you don't want to lose more insuation than necessary
until you reach the point of replacing the harness - but gently separate any
wires that seem too chummy with wires beside them.

If still no go, another thought: does the engine still stall if you unplug
the high beams? If not, I'm thinking the high beams are loading a voltage
down. I've had a lot of trouble with that separate terminal lug on the
positive post of the battery - one time it even caused the engine to die
when making left turns!

Mike