Gentlemen,

What kind of voltage out-put should I be getting, at the battery & alternator, with my 1990 240?

Thanks as always, Jon

When the weather was cooler i was getting a consistent 14.4-14.5V at the battery with the car on.
Now with the summer weather it is at 14.4V with a cold start but once hot, it will drop progressively down to 13.9V-14.0 V. This doesn't really matter cause even with all the accesories and a 1200W RMS amp, the alternator still puts out a steady 13.8V.


As long as you are anywhere between 13.8-14.4 V you will be fine.

A quick check on the condition of your battery and charging system requires a voltmeter, and a helper.

Check voltage at battery with engine off, and no accessories on.
should be about 12.6V (2.1V/cell * 6 cells in battery)
could be a little higher or lower depending on ambient temp
must be over 12V or something is wrong with battery.

Check voltage at battery with engine off, and headlights on.
voltage may drop a little, maybe to 12V, but not much more.
if voltage drops a multiple of 2.1, you have a bad cell in the battery.

Check voltage at battery while someone cranks the engine.
voltage will drop while engine cranks, but should not drop below 11V
if voltage drops a multiple of 2.1, you have a bad cell in the battery

Check voltage at battery while engine runs.
should see between 12.5V & 14.5V
15V or higher for more than a minute or three indicates overcharge
overcharging will damage the battery
regulator or alternator could be bad

These checks take about 30 seconds.

Good luck

91_240

My 90 240 had 14.4v at the alt.

The ideal way to determine if your charging system has been keeping your battery fully charged is to check the cells with a hygrometer (to measure their specific gravities) after the battery has sat uncharged (the engine off) for a few hours.

That said, however, if you just want to monitor your charging system and battery with a dash voltmeter, realize that your voltage regulator should actually vary the maximum batter charge based on temperature. When you first start out, you should find that your battery is being charged to about 14.3 volts (or more, in the winter) -- but as your engine compartment (and regulator, housed in your alternator) warms, you will find that it regulates to only about 13.8 (or less in very hot conditions). This is both proper and best for your battery -- if you check with Bosch books, and older "green" Volvo manuals (as well as MB manuals, etc.), you will find that they all show a graph revealing that the maximum appropriate voltage of your batter is temperature dependent -- higher in the cold, lower when warmer.

Note also that, dependent on the wiring that you use to hook up your voltmeter, it may not be that accurate (precise or consistent, yes, but accurate, maybe not) -- resistance rears its ugly head. Compare your dashboard voltmeter reading to a direct reading with a VOM on the battery's terminals -- then you'll know your "error" and be able to judge what's happening.

Regards

I just installed a VDO voltmeter on my 1990 244, and it shows 14 when the engine is running. About 12.5 when the key is on accessory.

Jason

To the best of my knowledge, it should be over 13V. The perfect is 14.1, if my memory and newfound knowledge serves me well.