Hi-

I bought a 1987 245 with 86k last October from someone who (it turns out) wasn't taking very good care of it. (And yes, I did get it for cheap). In November, I had both the battery and the alternator (a factory rebuilt Bosch) replaced. Just a few weeks ago, I noticed that the battery indicator light on the dashboard sometimes (but not all the time) glows dimly right after I start the car. The first time this happened it went out after 2 minutes, but now IF it happens (about once a week) it stays on the whole time the car is running for short (half-hour at most) trips. Also, even when it glows dimly, the car starts and runs fine. Only once has it "flashed" to bright, but then went back to dim. Like I said, it doesn't happen all the time, but I'm at a loss as to what is causing it and am concerned there is something more wrong with the car.
I generally don't trust mechanics, and would really like to get to the bottom of this myself, but am not totally sure where to start - instinct says to check the wiring harness and alternator connections. Where else should I be looking? I was hoping to use the car for some longer roadtrips this summer, but right now I just can't trust it. Please advise!
Thanks,
Kathryn

Hi Kathryn -

First of all, 86K on an 87 car sounds great - but the electric speedo/odo used from 1986 on has been known to act up. The odometer quits, or slips. Any evidence of that? If the inside of the oil filler cap has a lot of crud on it, that's a clue to higher mileage. Also the condition of the pad on the driver's seat - seen from underneath.

With new battery and alternator one would think things are OK. The alternator is mounted on rubber bushings, so there must be a grounding wire. It is black, usually connected to a bolt on the back of the alternator and the other end to one of the bolts holding the mount onto the block. Easiest to check with the oil filter removed - as during an oil change.

The other wires on the alternator are the aforementioned thin red wire, and a fat red wire. The fat one carries the heavy current to charge the battery, and usually doesn't go bad. The thin one has been covered - BTW it can be bypassed if it's bad somewhere in the harness.

The alternator drive belts can look tight when they're not. Push hard on them halfway between the alt. and the water pump, and if it gives over a 1/2 inch, they need tightening.

Cleaning the battery terminals is a snap using a brush thingie made for that job. Be sure to jot down your stereo tuner pre-sets first, as they may be lost when the battery is disconnected.

Good Luck,

Post back with how things go.

Bob

:>)

Thanks for the suggestions!

I haven't noticed the speedo/odo acting up, and I checked the foam under the driver's seat like you mentioned, and it looks fine. No crumbling or anything. Oil filler crap had a little crud the last time I changed the oil, but nothing extraordinary or alarming. (I guess the wife of the brother of the guy I bought it from did most of the driving, soccer-mom kinda stuff.)
Battery terminals are pristine, since it's a new battery. And the belts only give about 1/4 inch. No glazing or fraying that I can discern.

That said, I also checked the wires from the alternator, but couldn't get a good look at the black ground wire. The fat red one seemed ok, but the thin red one had some electrical tape around it about 2.5 feet down the line from the alternator, so it looks like it's been spliced already. Also noticed corroded wires on the battery ground cable (they were green where the plastic covering wasnt' protecting them), so I'm replacing that today. Is the wiring harness the sum of these 3 (1 black, 2 red) wires? What should I do about the thin red wire?

I also just bought a digital voltmeter, but haven't had the courage (or a friend with spare time to help me) to check the battery & alternator voltage. Any suggestions/tips on how to measure? How do I measure the alternator? (I'm a little clueless about electronics - it's been awhile since my high school physics class). Thanks again for your help.

-Kathryn

Hi Kathyrn -

So the "Tests" to see if the odo is accurately reflecting the actual mileage are OK. Good on Ya, mate!

I asked because I recently picked up a 1984 245GL as I needed a wagon, the odo sez 81K, the PO's history was incomplete, the leather on all seats is dust - sheepskins in place - BUT the oil cap was very clean, and the under-seat padding was as 81K. Since I have a non-op 1983 245GL with perfect same color leather seats, I went ahead and got the 84.

Now, about the alternator. Three wires, as you said. The factory color codes are RED - for the fat wire attached to the alt. with a nut on a stud, RED - for the thinner wire attached to the alt. on a spade lug, and BLACK - for the ground wire that is usually attached to the alt. under a frame nut and goes to a bolt that holds the mount onto the block. If your alt. has another colors, post with where they go.

There is another wire in the neighborhood. It's black, and goes to the oil pressure sender. It can go bad, too. If it grounds, the oil light stays on all the time. Not to be ignored if the light comes on while driving, but look at the wire right after checking the oil level.

All these wires are in the under-the-engine front harness, unless a PO has re-wired some of them. The thin red wire: You mentioned it has a splice some 2.5 ft from the alt. Where does the wire go after that?

The dimly lit battery warning light means, almost without exception, that the alt. is not charging enough. (Bright means no charge at all.) So the question is what sorts of things keep it from fully charging?

The ground wire is usually go or no-go, no halfway stuff. Same for the fat red wire, except that to get the charge into the battery, the battery cables have to be OK. You found that the ground side had some corrosion. The red on can also get corrosion up under the red covering.

The thin red wire is critical for with no voltage from it to the alt. there will be no charging. One check to do is to put the key in position II, the bulb check position, and then disconnect the wire from the alt. If the lights stay on, that wire is grounded someplace where it oughtn't to be. For the system to work, the ground has to be ONLY through the alt. rotor, NOWHERE else.

Digital voltmeter. I am still using a pre-digital Radio Shack cheapie, so any tips I have are just general. (1) Read the book about testing voltage. (2) See if you can test the voltage from a AA flashlight battery. A new one will read 1.5 to 1.65 volts. If you connect the test leads backwards, nothing gets hurt. You can do this holding the battery and one lead in one hand, touch the battery opposite end using the other hand.

Then check the voltages as suggested in the other posts. Across the battery terminals. Then from the battery red terminal to a nearby screw head on the body. Large voltage difference is a clue - check the ground strap between the firewall and a rear nut on the valve cover.

Post back with how things go. I have the Volvo Service Manual Wiring Diagrams for your car and can look further. BTW - you might consider getting said manual. Look at http://www.volvotechinfo.com/index.asp to see if they're available. Pricey but a very worthwhile purchase for your Volvo Library.

Good Luck,

Bob

:>)

bob-

ok, let's see, where to start... no other wire colors from the alternator than the 2 red & one black wire. (i STILL can't find the black ground wire coming from the alternator - i haven't attempted jack stands & removing the splash pan to get under the car for a good look yet. the ground wire that had some corrosion was the one from the battery - cleaned it off with baking soda and water and a toothbrush. there is also some minimal corrosion on the red battery cables tho). but as for the 2 red alt. wires - the fat one looks fine, no corrosion or anything. looks new even. as i mentioned before, the thin red wire looks like it was spliced and wrapped with some electrical tape about 2.5 feet from the alternator. after the tape, it's about another foot or so to the little gray box located right next to the firewall (there are about 8 connection points in the box - 2 across, 4 down - and the red wire is stuck into the 3rd one down on the right side, if that means anything).

i didn't disconnect the thin red wire and put the key to position II to test it yet (i need the car tomorrow and wouldn't have time to fix the problem anyways...maybe i'll attempt it tomorrow night.)

oh, and now for the questions:
exactly how do i measure the voltage coming out from the alternator? should the car be running? the positive point from the voltmeter should be touching what on the alternator? the black voltmeter wire should be touching a screw on the body frame, right? or do i connect from the battery to the alternator? also, do i measure this in dcv or acv or something else? what is the proper alternator voltage reading?
also, how do i measure the voltage of the ground strap running from the valve cover to the firewall? i got a reading of 0, but i might have not read it right - the red point of the voltmeter should touch the valve cover nut, right? what kind of reading would you expect to get here? i don't see any corrosion here, but it is awfully grimy looking.

the voltage between the battery terminals is 12.5, which is good. i tried measuring from the battery red terminal to a screw head on the body (with car not running), and got 0.05. you mentioned a large voltage difference is a clue - but a clue to what???

for what it's worth, havent' had any problems with the oil light going on either.

thanks for your patience - this is the first car i've ever owned!! i'm learning tons...
-kathryn
ps. just bought my first socket set - it's so exciting.

hot sake,

Check the little red wire attached to the back of the alternator.

I have an '86 and it suffers from the same wiring harness decay syndrome as your year, I believe. The little red wire often breaks free from the connector, or the insulation decomposes (it runs under the front of the engine - brilliant engineering on that one!). A nastier problem can be that it looks like it is attached but has become corroded inside the female connector.

Clean/replace the connector at least and perhaps the harness that runs under the front of the engine.

Good luck!

TomD

i had this problem on an '84 245. mechanic repaired it by making more tight a ground wire (or some other sort of wire) to the alternator. i know this isn't a huge help, but it seems to me your instinct to check the alternator connections is a good one. good luck!
-chris
'84 264 Diesel

The first step should be to check the voltage at the battery between the hot and any nearby screw on the bot, and the between the battery post. You should see the same voltage , 12.5 - 13.25 vdc.
If the voltage is different, pull and clean both the negative battery lead AND the bolt making the body ground connection. While you're at it, pull and clean the ground cable to the engine block. You should see a voltage improvement. If not, I'd suspect the battery ground cable is breaking down.
--
There are no stupid questions only those that are not asked.