The second I connect the battery a noise comes from somewhere near the differential. The key is in the off position, and I have systematically removed all fuses. Does anyone know what this might be. It sounds like it could be a fan or pump possibly.

maybe a bad rear wiper motor???

Something else at the rear that could run is an electric antenna motor - with something damaged in the mechanism that does not allow the antenna to move.

You should be able to find the source of any noise!

Try using a 4 foot length of heater hose with one end at your ear and scan around with the other end.

As you know, many think that you are a suspicious character.

What do you think?

"What do you think?"

You're right. Electric radio aerial. Perfect explanation.
--
Art Benstein near Baltimore

"Any intelligent fool can make things bigger and more complex. It takes a touch of genius - and a lot of courage - to move in the opposite direction."
-Albert Einstein

I have arrived!

An attaboy from Art Bernstein! ( one of my Volvo heroes )

Come on James. You were here long before I stuck my nose in.

I don't care what our OP comes back to say it was (if said at all) after methodically removing all the fuses. Your thought was beyond my ability to guess. This and I even just recently had an electric aerial apart on the bench in an effort to help someone up in Canada.


--
Art Benstein near Baltimore

My dog is worried about the economy because Alpo is up to $3.00 a can.
That's almost $21.00 in dog money.
-Joe Weinstein

Hi,

Stick an ampere meter in between the negative cable and the negative post on the battery and find out how much the drain is drawing. This checks the whole car.
This will give you a clue to what item or items are doing the drain.

When you first replace the cable there will always be a tiny spark due to the dash clock or the computer charging up their capacitors. It should only be a few milliamperes at best fir a second or so.
You want to see only a steady reading in the neighborhood of .002 -.050 parts of one ampere max.
You have to watch which scales are being used or if on the auto seek scale, watch the decimal point movement.

If you can hear noise from the differential, that at the back of the car, while at the front of the car with the battery, you have a lot better set of ears than me!
If you are walking around, then yes, I believe it's a pump or something.
That should not happen unless a relay is stuck closed and the other poster it pushing you to the right place.
Unless the wiring is totally screwed up there is no way they should run with the switch off.

Get back to us with more clues, as there is a logical reason for this when it comes to electricity!

Phil

I ran into this once, where it was the fuel pump. The occasion was an impromptu stop at a local garage after seeing a 245 parked in front for months. I was curious, and that day had the time during business hours to make a visit.

Turns out the car had the shop stumped. Wasn't that easy for me, either, but I got it going for them. The issue with the fuel pump coming on with the key out was a jumper wire (like what we'd use to bypass the fuel relay) was run between 4 and 6 behind the fuse panel by someone even before the shop took on the project.

Cars this old can't be trusted to have the wiring they were born with. And in a 1987, the failing insulation on the main engine wiring harness could do all that on its own, without monkey business. Look under the vinyl sleeves.

By the way, the ammeter readings you note, Phil, are not so steady if there's a working clock in the dash. Boing, boing, boing.
--
Art Benstein near Baltimore

Why does the seven segment display have decimal point at the right?

Hi Art, maybe I have arrived too!
Sousa's post was humorous but accurate on getting that "oh, I feel great feeling" having The Volvo guru recognizing the "probability" of a good answer.

Yes Boing Boing is the way the clock works. Like a pogoing stick, that needs just a little more effort on the down stroke, to make it go again!

My intent was to explain the "tiny little spark" when the battery is first connected.
I know you know and so do some others.
Some observant people see it, but that is far as it goes!

Not everyone get an education by pure unadulterated and simply explained facts these days.
Most books do get carried away with too much theory and we nod out. Or some give it the so called "hood wink" and say, oh, I got all of that, BS!
Believe tme that there are plenty of those standing around in a stupor!

It's these tid bits we pick up in life that are seen to work that get the most easily remembered.
Even though we may not know exactly where they come from.
I'm dropping hints of what I can, like a dirty little bird does (:) and see if it helps to get a reaction of, "Hey, I found and fixed that!"
I feel it how we get self-confidence to do more and then dig into more details!
Not just wait for an answer but become self reliant.

The stuff just doesn't get poured into out heads or comes in a pill today! I doubt it ever will, IMHO!
So much to learn and so little time! Once you get to reading for the things you want, the more you find that out!
Some ancestors wrote and speak very loud on good subjects to save us the time.

It is really just the capacitors everywhere taking that first sip of power.
Once the capacitor is charged it acts like an open circuit and that small drain, goes away.

It the overall specifications, of what could be on, I was suggesting in order to find a culprit.
This is then the beginning of that person to looking into how the systems work together!
We started grade school with little square building blocks.
I think DVOM's should be in their hands today!
They will have good reasons to learn numbers and the math of what's really in the cosmos!

Anyway, with our playtime here on the BB, we might be able to remove some of the fears, in Volvo drivers, for that mysterious electricity stuff!

Phil

Sounds like a fuel pump is running. Check and or pull the relay that sits on the fire wall below the glove box. Even easier would be to pull the 25 amp fuse by the PS reservoir