Date: Thu, 26 Aug 1999 14:31:19 -0700
Reply-To: Coby Smolens <cobys@WELL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Coby Smolens <cobys@WELL.COM>
Subject: Re: Which Voltmeter to use?
In-Reply-To: <4.2.0.58.19990819140851.00cd7500@pop01.ny.us.ibm.net>
Content-Type: text/plain; charset="iso-8859-1"
I like David's list, I would add only one thing to the "should-have"
section: Min-max record. This is invaluable (read that extremely valuable)
in finding "drop outs", as in when a bad temp T2 sensor in an aircooled van
reads just fine in the shop, but suddenly kills the engine on the freeway.
With min-max on you can record the battery voltage spike that occurs when
the resistance between the sensor and ground goes to infinite. Or you can
record the voltage return to the ECU from the airflow meter and pick up the
voltage drop when the circuitry in the meter breaks down momentarily. These
things tend to happen too fast and too sporadically to be tested for in
bench test conditions.
Coby Smolens, Owner
Valley Wagonworks
"Intimately acquainted with VW Vans since 1959"
1535 Sir Francis Drake Blvd.
San Anselmo, CA 94960
Phone: (415) 457-5628
Fax: (415) 457-0967
http//:wagonworks.com
mailto:contact@wagonworks.com
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
Of David Beierl
Sent: Thursday, August 19, 1999 11:30 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Which Voltmeter to use?
At 16:26 8/19/99 +0000, Jeff Gilbert wrote:
>Hi,
>
>Im new to all this diagnosis stuff and was wondering if someone could shed
>some light on what would be a good voltmeter to aid in the diagnosis of a
>never ending, son of a bitch, fuel injection problem. Bently suggests
>using the VW meter...is this necessary, or will any good quality meter do?
I would suggest a meter with at least ten megohm input resistance on DC --
most digital meters will meet this, while cheap analog meters may have only
a few thousand ohms resistance on low volt scales. Accuracy of +/- one per
cent is plenty. Desiderata include:
Removable test leads with banana plugs -- there is a wide assortment of
leads available with clips, interchangeable tips etc.
Separate connections for volts and amps -- this is a nuisance but sooner or
later will save you blowing a meter fuse or worse.
Ten amp range -- actually you can build a shunt to measure any conceivable
current but it's a pain.
Bar-graph meter display which reacts faster than the numerical display.
If auto-range, switchable to manual
Diode-check voltage of three volts -- this isn't common, but it will let
you check most LEDs. Usually it's 1.5, which is fine for regular
diodes. Not a biggie...
Continuity beeper -- these vary widely as to what the consider "continuity"
so read the manual. Some are as high as 1500 ohms, which isn't very useful
in an automotive setting.
Low DC volt scale that lets you measure ten millivolts or less -- most
digital meters have this.
Peak Hold -- holds peak reading until you release it. Handy, but not
common.
Differential Reading -- once you designate a reading, meter displays
difference btw that and the current reading. Handy, but not common.
Ohms scale ten megohms or more. This is common, but the cheapies sometimes
only go to 1 megohm; acceptable but not desirable.
Things that don't matter:
True RMS reading -- this is only for AC. It's a good thing, but no help
with the van.
Capacitor testing -- good for electronics, but seldom useful with the
van. It will show the value of a cap, but won't show whether it breaks
down at operating voltage.
Transistor testing -- only electronics
Super accuracy -- nice to have, but it costs out of proportion.
david
David Beierl - Providence, RI
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
