Board logo

Cheap multimeter
graememk - 20/8/07 at 12:39 PM

either my cheap £10 multimeter is really really crap or my indy battery is chucking out 15.4 volts without the engine running and 17.8 with the engine at 2000rpm.


sort of messed with my re wire on sunday.

Bluemoon - 20/8/07 at 01:08 PM

Sounds like you regulator on the Alt is possibly nackered. Try the multimeter on a new alkali battery battery it should measure about 1.5 to 1.6V this would check the meter (on the same range that you used on the indy).

You could also try the same measurements on the tin top to confirm if this the readings are to be believed.

Dan

[Edited on 20/8/07 by Bluemoon]

iank - 20/8/07 at 01:33 PM

The multimeter isn't switched to diode test/continuity/resistance rather than voltage is it?

Seems very high even when the engine is off which is strange.

02GF74 - 20/8/07 at 01:59 PM

maplins sell digital multimeters for about £ 5.

sounds like your mulitmeter is knacked or needs to have battery replaced if DVM.

lead acid battery should not be giving out more than 12.5 V (engine not running).

as ^^^ said, test the mulitmeter against a known voltage e.g. mains but that may not necessarily prove it is working since you would be using a different scale./range

martyn_16v - 20/8/07 at 08:51 PM

quote:
Originally posted by 02GF74
known voltage e.g. mains


Mains isn't always 240V, it can vary by quite a lot (we don't actually officially have a 240V supply any more, it's 230V -6% / +10%), certainly enough not to be the greatest reference.

If you have a megasquirt you could measure the regulated 5V (the TPS +5V amongst other things). If not, i'd imagine most ecu's will use a regulated voltage for the TPS (either 5 or 12v). Failing that, if you've got an old tintop instrument panel kicking about it'll more than likely have a 12v regulator on the back you can check off.

Peteff - 20/8/07 at 10:45 PM

A fully charged lead acid battery should read nearer 12.7v. When it gets down to 12.4v it is only 75% charged and will start sulphating and eventually not accept a full charge. If you can, get a hydrometer to test the electrolyte.