None of the lights work

dbraddock · Post by **dbraddock** » 05 Jul 2015, 12:46

Not sure if I am doing this right. The battery in the Volvo is dead right now so I jumped it with my other car. WITH the cables still hooked up I was getting a reading at 12.5 at the battery and the alternator. Once I took the cables off it dropped to 8 at the battery and alternator, within 30 seconds the car died.

matt122s · Post by **matt122s** » 05 Jul 2015, 13:20

I'm pretty sure you need a fully charged battery to perform the alternator output test. The proper alternator output is between 13.5 and 14.4 volts at the positive battery terminal at idle. If it's below 13.5 volts then it's not enough to charge the battery and it won't keep the car running, especially if you put on the car accessories.

dbraddock · Post by **dbraddock** » 05 Jul 2015, 13:24

I hooked up the battery from my z and I am getting the same reading at the battery as I am at the alternator, 12.5. I don't see the ground for the alternator. There is the positive red cable and there is a another wire that splits off the same harness that connects next to the positive. The only ground I see appears to be running into the compressor.

Post by **abscate** » 05 Jul 2015, 13:47

The alternator probably grounds through the case not a direct wire. Loose or missing ground straps will give you problems, though. Do you have a wiring diagram?

Post by **BEJinFbk** » 05 Jul 2015, 13:49

With low voltage, a lot of weird stuff can happen.
Any decent parts store can get you started with a
charging system diagnosis using a specialized tester
in their parking lot. Just be careful about getting in
a hurry and spending a lot of money before you're
sure of what's going on.

Get some data and post back - We can help.

If you're seeing less that 13.8 from the alternator
when the car is running, it has a problem. It may be
as simple as a new voltage regulator.

The regulator for your Volvo is a replaceable part of
your alternator that monitors the car's system voltage
and tells the alternator whether it should be producing
power or not. It's MUCH easier to swap the regulator than
the entire alternator. If you still have a factory alternator,
it's an even lot better idea as many of the rebuilds out there
are absolute junk. The OEM is worth keeping if possible.

The cables, connectors and battery are the other major
parts of your primary power system. Be sure that all of these
components are solid before you dig deeper into the first things
that you described. Search "Voltage Drop" to learn more.

A good charging system may well alleviate the other issues.

dbraddock · Post by **dbraddock** » 05 Jul 2015, 14:43

the lights issue is solved. With a good battery I am getting a 12.5 reading at the alternator. Basically Im getting the same reading at the battery as I am at the alternator both with a good and bad battery.

I wasn't aware that the regulator can be replaced separately, it appears to be an easy removal of just two screws. The alternator is bosch and I believe to be original but it might have been replaced with an oem for all I know.

Post by **erikv11** » 05 Jul 2015, 15:18

You want to do that test with the car running: V at the battery and at the alternator. If the alt is bad then it could be killing your battery(s).

Replacing the voltage regulator is a standard fixit for the alternators on these cars, just be sure you put in the same kind as came out. There are a few different types of regulator and they are matched to the alternator. You can replace the voltage regulator on an NA pretty easily without even removing the alternator from the car.

dbraddock · Post by **dbraddock** » 05 Jul 2015, 15:28

That's great news, maybe Ill make a trip to the junk yard and grab a few. Is the difference by serial number or are they physically different?

You guys are awesome, thank you all for quick responses. Your help has been truly priceless

matt122s · Post by **matt122s** » 08 Jul 2015, 06:19

Hi dbraddock,
I was doing some other work on my '95 850 recently and I had the alternator out. While it was out I replaced my voltage regulator and both bearings. The regulator is really easy to change with the alternator in or out of the car. I bought my voltage regulator from a seller on Ebay called "california_alternator_starter" . Super easy to deal with and it was a great price and shipped to Massachusetts quickly. It was around $20.00 and included free shipping. I hope that helps, it doesn't sound like this is your daily driver so you might be able to wait.
Matt

Post by **erikv11** » 08 Jul 2015, 08:27

dbraddock wrote:That's great news, maybe Ill make a trip to the junk yard and grab a few. Is the difference by serial number or are they physically different? ...

They VRs are physically different, really you want to eyeball the one in your car to be sure, or else you could grab a whole alternator from the junkyard.

Check this post, it is long but it has detailed info about the two most common types of VRs on the 850s: https://www.matthewsvolvosite.com/forums ... =1&t=61610

None of the lights work

Re: None of the lights work