I Always check the voltage at the battery, then check the Voltage at the Component under test, i,e Starter motor or Alternator, If these check out Ok, then theres no need to do a drop test on the cables but if there is a discrepency between the two readings then the Volt drop Test is the way to go to identify which cable is to blame.

As Dave has said, it was a must on the Cavaliers and With this test on various cars we have found Bad alternator Earths, Either through the earth strap or even through corrosion on mounting brackets - Alternator to Bracket or Bracket to engine on some cars, One that comes to mind was escorts.

Transits and some cars suffer with bad connections where the Terminal is Crimped onto the battery cables due to being crimped at the factory and not soldered.

One Cavalier that I checked Even suffered with Bad Alternator to Cylinder head Earth strap, a Bad Earth Between Cylinder head and Cylinder block and a Bad earth between Engine and Gearbox, several earth straps later and it was charging fine. So its not always a fault with the cables.

Escorts were terrible for starting and charging faults and we regularly found lots of volt drop on the whole starting and charging system, every cable and every joint had a small volt drop but mounted up to possibly something in the region of 2 volts when charging with the lights, wipers and heater etc turned on, So they always used to have flat battery problems in the winter, The Cure was to remove alternator and mounting bracket, clean off all the rust from the brackets and mounting bolts, Make up a new alternator harness and solder up the joints in the ring terminals on the battery / starter cables. The Result was a car that would charge at 14.4 volt ish with no load and around 14.2 volt fully loaded compared with 12 - 12.8 volt previouly and no more flat batteries.

Who said old cars used to be good. But they were reasonably easy to fix.

They used to be proper Electrical jobs where we could do a job and charge for the amount of time spent fixing it as you could prove the problem and guarrantee the fix, Not like the Modern cars when it goes downhill from the Point where the Customer says --------- DO YOU DO DIAGNOSTICS. ????? I HAVE A PEUGEOT DIESEL AND A WARNING LIGHT OR 3 HAVE COME ON AND ITS BAD STARTING AND GOES INTO LIMP HOME OCCASIONALLY AND THE HORN DOESN'T WORK AND THE INDICATORS OVER CANCEL.... ARGGGGGGGGHHHHH LET ME OUT.

P0335 crank sensor, rail pressure too low, rail pressure moitoring, clutch switch, can communication failure, Air con sensor. etc etc etc

And What "TIME" Will it be ready and how much will it be. ??????????????

Tony.