Hammers and chalk.  Paid to have the fault fixed.  Fault was fixed.  You owe
the contract price whether he put a chalk mark on the critter or tapped it
with a deadblow hammer.  Regardless, it is fixed and if you agreed to a open
contract then the fault is yours.

The real question is not whether the fettler (feller who fixes stuff) should
be paid his price because he FIXED the problem. Of course he should.  The
real question is whether he should be paid a 'consulting' fee when he DIDN'T
FIX the problem

As a consumer I employ various tradesmen, mechanics, professionals, and
'automotive technicians'.  The followiing applies to all of these folks.  I
pay them to fix a problem, if the analysis of the problem requires
troubleshooting and time to FIX the problem, I have no cause to question the
bill.  If the problem is not FIXED I feel I do not owe the shop for it's
time spent 'looking at it'.  I pay for results not 'action'.  I expect
results not mere 'action'.  The wise shop will so state that if they don't
meet the contract requirements to repair the problem then the contract is
unfulfilled until the problem is fixed.

You wouldn't pay the Almaguer brothers to drive by and look at your lawn,
you pay them to mow the grass.  If the grass is mowed by magic, so be it.
If mowed by lawnmower so be it.  If it remains unmowed no fee is due.
Didn't meet the requirements of the contract to 'mow the lawn'.

A professional should be able to estimate the time required to analyze the
problem because he is a trained and knowledgeable professional.  His expense
to learn to troubleshoot the particular problem is adding value to his
business and is at his expense rate (far below flat rate) If he knows
nothing about the system on which he is working then he is learning and
enhancing his value as a service provider.

You didn't pay him flat rate to LEARN on your van, you paid him to FIX your
van.  Ask relevant questions in advance.  Make sure you both agree on the
price estimate and that you as the contract participant have a written,
signed estimate before you leave the premises.  Here in CaliFUNia that is a
requirement.  In Washington state, if a signed written estimate is not
provided in advance there is no contract for the work and you may argue that
it is not your responsibility to pay.  Peruse Washington State site for
details.

In the end, hire those you trust.  The less than trustworthy business will
wither and die of their own accord.  Lookem up on Angies list.  Agree on the
contract requirements and read every line before signing.  The honorable
business will not be offended.  The dishonorable business will give itself
away by obstruction.  Take all the used parts with you.  If something was
replaced you should have the replaced item.  This is where Sears and Sawbuck
got in trouble some years back.

Almaguer Bros are fast, efficient, likeable, and mow like the devil is after
them.
Stephan's Autohaus, Transaxle Engineering, Jeff Schwaia's shop, and
Mastercraft Motors and Infinite Fabrications also pass muster as excellent
shops.  There is a welder here in Sacramento with whom I have an 'open
account'  Arturo is a magician with a torch or an arc.  He's fair, honest
and still in business after some layers.  AVP, Leonard and Erin, also are
still here doing business.

The restaurant is only as good as the last meal you ate there.