1999 S70 Charging Issue

[volvooh]

I replaced the alternator in my 1999 S70 over the weekend. I had it initially checked at an Autozone as a bad voltage regulator. The charging system was not keeping up with the cars needs and weekly required a few hours on a battery charger. If not, low voltage issues such as shifting problems arose but went away after charging. At no point though did the battery light come on (does come on at start-up)

So I found a pull off alternator at a local yard and installed. I went ahead and invested in a multi-meter. When I put it on the battery it read about 12.3 Volts. After starting, it read about 12.8V under load (all accessories on). Similar tests on my other Volvo 70 models came in at 13.3 to 13.6 under a similar load.

So I started to play around a bit. I found that when I tested the positive cable coming off the alternator while grounding on the battery it had a similar reading, about 12.8V. However, when I changed the ground to the engine while still testing the positive cable coming off the alternator, my reading jumped to 13.8 V. Somewhere I am losing about .75 to 1 volt.

Going back to the battery, I tested the positive side to the to grounds that come off the battery that are fastened in front of and below the battery box. Going directly to those grounds I am only getting a reading of about 5 volts. So clearly, I have a grounding issue. Upon further inspection, I noticed the ground fastened to the frame has an additional leg, meaning, it goes from the battery to the frame then off some where else- I am assuming the engine block, but that has been severed (looks melted).

So my question is- does any one know where that leg would go, and can I simply run my own ground cable from the battery to the engine or frame?

[abscate]

You need good grounds from engine to frame, battery to engine, battery to frame.

Probably best to get a notepad and a wiring diagram, locate all the ground wires, and replace them

[Ozark Lee]

Typically there is one real heavy gauge wire that goes from the terminal to the block and then a secondary that taps off of the battery terminal itself and goes to the chassis. As Steve pointed out, they are both important as are the braids that go from the block back to the firewall. From past experience I have not done real well with trying to make battery cables using the after-market battery terminals that you slip the wire into and then bolt down a clamp to make the connection. That type will work in a pinch but after a couple of months the connection tends to corrode and things get bad again.

From a wallet perspective even after-market negative battery cable assemblies cost just shy of $100.00 but that isn't something that falls into the OEM only category IMHO. If you can get an OEM cable in the same price range then I would certainly do so but if the OEM is twice the money then I would use an after-market like Dorman or someone similar that has factory made terminals without any real reservation.

...Lee

[benpineapple]

I was having similar issues recently, ended up being a combination of corroded grounds point and a bad battery terminal I had spliced on to the old battery cable. If I were you, I'd clean up all ground points, then measure voltage. If you're still seeing a drop, even if it's a bit less than the initial 1-.75, I'd replace the cables.

Make sure you get the body ground that is tucked next to the air filter box on the driver's side. I didn't see it until I pulled diagrams that said it would be there.

[volvooh]

Thanks for the insights. I'll be sure to clean-up the grounds by the battery cables. Any one know where the ground attaches to the engine block?

[benpineapple]

Ignore arrows, only overhead pic i could find. Ground cables that go to the block are circled in red. 10mm bolts on either side.

[Ozark Lee]

The main (real heavy gauge) cable bolts to the block by the starter, more or less below it as I recall.

...Lee