I salvaged the stock voltmeter gauge out of a 240T and installed it lastnight in a '83 245DL. At first I had it tied into the power for the small clock , but then it would be always on. So instead I have it spliced into the radio's power wire (switched). However, It's reading about 1.5 more volts now than when it was tied to the clock. Seems strange to me, any ideas? Thanks

Tie it right to the battery terminal or the battery terminal on the starter.

Thaks a lot everyone. I've decided to go with Art's location so I can have something to look at while I crank the engine.

According to the Volvo intructions for the Voltmeter,route the red/blue wire from the cable harness to the fuse box . Connect to fuse no. 13.

Out of convenience, I hooked my voltmeter up to the same line that feeds the constant voltage to my CD player. No problem at all with current drain, since the voltmeter has an internal resistance of a few hundred K-ohms. I can see if the battery is low before I hit the starter on these 0-degree mornings... Bottom line, the best is to run a line to the fuse block, but 2nd best is almost anything else that's powered while the car is running.

Jon, as you have an 84 you have the option of using the same trick I used with the voltmeter. In order to use it before, during and after starting your motor, it can be connected to fuse #4 (83-84) which fuses the "key in" line to the chime. This fuse has power on it whenever the key is in the ignition, regardless of the position. I can actually see the battery voltage while cranking, though it is in the red on the expanded scale.

Yes, the voltage will vary depending on where you connect the meter in relation to other loads and where it is grounded. Ideally you'd have it go right to the battery, but then it would be on all the time. So for a switched connection, fuse 4 is as close to the ignition switch as any, voltage-drop-wise.
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Art Benstein near Baltimore

tying a gauge directly to the battery is not a horrible thing, Art.

A battery in good enough condition to operate a car would be drained by a voltmeter in about 10,000 years.

I just can't help myself, guy.

You're right, I think, if you're saying it wouldn't hurt to run the wires out to the battery for an accurate measurement. Or at least, a repeatable measurement; accuracy is not a strong point with these OEM gauges.

The current drawn by the voltage gauge (50mA) is about 1000 times greater than the residual drain used by the radio and ecu memory not counting the 5mA once-a-second spike used by the clock. What might surprise you, is it is half that used by the 1.2W lamp that illuminates it. I was lazy about wiring the lamp, so that would have been 150mA for me.

Auto batteries are built mainly for cranking, so amp-hour ratings are difficult to nail down for long-term small loads, a performance they are significantly derated for. So a typical 50 amp hour rating that will run your left-on 10 amp lighting for 5 hours won't necessarily keep your 1 amp dome light pair on for 50 hours. To run the Volvo voltmeter for 10,000 years you'd need 10000 * 24 * 365 *.05 = 4,380,000 amp hours in that battery, er atomic pile.

So, I figure if you connect it to a good battery, you'll need to jump it if you leave it parked for about four weeks. 'Course if you wire it through the switch, you could probably get away with parking it for a month. (smile)
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Art Benstein near Baltimore

"...drained by a voltmeter in about 10,000 years..."

240s have been known to last that long.
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Don Foster (near Cape Cod, MA)

yes but will the clock still work??
Bret
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rust free in west Texas

They have in the past, so should in the future.

Time will tell.
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Don Foster (near Cape Cod, MA)

Now that's the Don Foster we used to know!
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Art Benstein near Baltimore

I'll second that.
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Don Foster (near Cape Cod, MA)

It needs to be tied into a switched +12v line. Your readings will vary by circuit depending on how much voltage drop there is or whether it is "regulated". On the 1984 wiring diagram the voltmeter is tied to the fuse labeled "gauge".

Have fun,

Justin B83 244 Turbo

You will receive varying responses on this, but I tied mine into the fuse panel, THe fuse # escapes me at this point though. Its An easy run and clean installation as you can use a spade terminal. I'm not an electrical engineer but it seems to me as the most logical place to tie into as you arent dealing with any other voltage drops. Note: These gauges are not terribly accurate and serve as a gross approximation as to the state of the charging system. USe a volt meter to see how close the gauge really is.

Matt

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'82 DL - 153k, '93 945 - 102k