My 1987 740 manual with push button overdrive and turbo, made in Sweden, is my pride and joy. However last winter I had to jump it all the time to get it to start so I put a new battery in. Seemed fine. Then it sat for about a month+ and I tried to start it up yesterday, no juice. Jumped it, put the battery charger on. But I'm thinking something is draining the juice. Friend put a tester on the alternator and said that part was fine. When I had it running, I did note that when the lights were turned on, the needle indicating battery power really dropped down low.

Any ideas? I'd like to keep it but it's also starting to get really weird millage, sometimes down to 12 or 16, then will jump up to about 26 mpg, no reason, same driving, same roads, etc. Has about 290,000+ on original engine.

I got talked into getting a 2005 Subaru outback wagon, AWD, looks nice but it only gets 20 mpg and that's only if I drive like an old woman. I don't want AWD!

So if I were to trade off the 1987 for a diff Volvo wagon, any recommendations?

Maybe I'm missing something...

"Friend put a tester on the alternator and said that part was fine"
What did he actually do to come to that conclusion?
Was there a load on the alternator when he tested it?

"when the lights were turned on, the needle indicating battery power really dropped down low"
I think you mean the volt meter, not battery power meter. Still, this indicator is inconsistent with what your friend found.
Did he test it on the car?
What did the volt meter show while he was testing it?

Do the lights brighten if you rev it up a little?
If you turn on other accessories (while the lights are on) do the lights dim?

I don't think the mileage inconsistency has anything to do with your charging issue.
Could you have calculated it wrong?
Did you fill up with E85 by mistake?
Could the mileage recorded been off by 100 miles or so?

"talked into getting a 2005 Subaru outback wagon...only if I drive like an old woman"
I've been accused by my wife and daughters that I drive like an old woman. They've never been in the car with me when I'm alone though...
I still have no interest in a Subaru. Currently have RWD with snow tires.

"if I were to trade off the 1987 for a diff Volvo wagon, any recommendations?"
No. Because full size wagons with a stick are a dying breed in the US.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig

OK, so yesterday I drove the Volvo and noticed the battery indicator gauge on the dash held pretty steady at the mid-point, went down if turned on the lights and went down when I pushed in the OD button. Sometimes the car doesn't shift immediately into OD and I noticed that even when it didn't shift right away, battery gauge dropped as soon as I pushed in the button. Any idea what's up with that?

Thanks for any more help you are able to give.

Judy

If this is a parasitic drain as opposed to a charging/voltage issue, you can remove 1 fuse at a time(start with the circuit that feeds your glove compartment light) when you are going shut the car off for a couple days. Eventually you will find the circuit with the "parasitic drain" because when you pull the fuse for the affected circuit and leave her to sit....the battery will not drain(with that 1 fuse removed).

Still waiting for voltmeter checks. And your wiring. Look at the grounds on top of your manifold. It the insulation is breaking down, then you have the old harness. Some 87s got the new improving wiring harness.
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Not been able to get voltmeter checks, all I've got is the needle in the battery gauge in the dash, goes from 10 to 16. However yesterday I drove the Volvo and noticed the battery indicator held pretty steady at the mid-point, went down if turned on the lights and went down when I pushed in the OD button. Sometimes the car doesn't shift immediately into OD and I noticed that even when it didn't shift right away, battery gauge dropped as soon as I pushed in the button.

I know I've got the old i.e. bad wiring harness.

Without voltmeter checks, you're just guessing. I would say you OD not shifting immediately has nothing to do with your volt gauge. Venturing a guess, alternator. Original? Brush replacement is pretty simple.
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yeah I know I'm guessing.

I've replaced the alternator once, about 5-6 years ago. Suppose I could do it again but I'm not convinced that's the problem.

Anyone want to buy a really sweet red Volvo w/some issues?

Hello Jaloring,

A shorted alternator diode could slowly drain the battery away (by not able to properly charge the battery during each use).

See:
http://www.aa1car.com/library/battery_runs_down.htm

You'd need a voltmeter to test for this. Or you could bring the car to a alternator repair shop to diagnose. If you choose to do the first, set the voltmeter to AC (alternating current reading), engine running, one probe to the B+ terminal on alternator and another probe to ground (alternator body). Probe polarity doesn't matter as AC goes both ways.

The reading should be less than 0.5volts. If more than that one or more of your diode(s) may have shorted.
Yes the car could still run with parasitic AC in the system but the delivered voltage going to be less than 14volts leading to undercharged battery (plus low reading under load at the in-dash voltmeter).

Hope this helps,
Amarin.

Thanks so much, now I understand why a voltage test is important. It'll take me some days to find the right place. Will let you know the results.

You have an 87 740. Thus, you have terrible wiring. These are known for that.

I just read a thread elsewhere in which, same year car, he chases electrical things with new parts of all sorts, only to find degraded wiring inside the harness sleeves. With your range of issues I think you'd best look at grounds and the wires themselves.

so many questions.

ok, wasn't really a friend, was a worker at a local NAPA store who claimed to test the alternator when I was trying to determine if the battery was bad. Ended up replacing the battery.

as for lights: when they are on, the needle on my dash gauge drops a bit; the gauge goes from 10 to 16, w/o lights on it runs at the half way point, I'm saying 13, when lights are fully on, drops to probably 12, if only parking lights then not so much of a drop. I wasn't able to get a volt meter to really do more accurate of a test.

I suppose someone could have siphed gas but that would be highly unlikely. I live in rural W. Montana and the car is either at my house in the country or right out front my office in a small town where that would be noticed. I've been keeping mileage records for many years and so I think I have a good handle on the calculation and I'm saying it fluctuates a lot and does not get near the mpg it used to. I used to get 28 mpg real steady 8-10 years ago. I will admit that I've been a bit cheap on the quality of the gasoline however.

I do agree that the Volvo wagon must be saved. Just wish I knew more mechanic stuff. I've got another headliner for it and had dreams of changing that out and getting a good paint job on it but seems like I keep having driving, etc., issues.

Thanks guys.

First you need a voltmeter to check the battery, static, at idle and reving up the throttle. Post the numbers here. What method did you use to measure miles per gallon?
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Will get to measuring later today and post results. MPG measured by keeping
track of gallons and miles driven, I always fill it up so is easy to do
that.

Never seen a car drop that much in mpg then go back to normal. Are you sure no one is siphoning gas from you?
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