I didn't and don't disagree with you Lenny - sort the brake lights out first then put it on a code reader if that doesn't knock the lights out. If you've got a reader you could do that first, but people usually don't so it costs them to get it hooked up.
You're the lucky one to have had a voltmeter when you were a lad - I just had a couple of bits of wire and a light bulb
As it happens, I've had the 3 Amigos twice on my Freelander and both times the main modulator has been goosed. Doesn't seam to happen to others, just me!
I BUILT my voltmeter out of a 1mA meter, a wooden case, some brass tube and some resistors.
Frankly it was probably better than many of the chinese trash boxes you can buy today.
I still favour an analogue meter where you can see the needle flicker compared with a digital that just rolls numbers at you.
You can buy a cheap analogue meter for less than a fiver these days.
Its good enough to track down most car problems with.
Also dont diss the benefit of clear logical thinking, a circuit diagram and a knowledge of electrics.
Or of basic and simple tests.
I used to set up ignition timing entirely by ear eye and test drives. Measuring against the actual spec with a strobe usually showed I was spot on.
On the FL1 at least, the circuit goes battery->big fuse -> little fuse-> switch-> lights. There is no electronics in that path, merely a sensor for whether the brakelights get power or not, which clears the two amigos one supposes.
ABS light is more complex.
The point being here, that no brakelights means stuffed switch 99 times out of 100 and stuffed switch always lights the two amigos.
You can check the switch: the outer two contacts on the three terminal switch should make contact till the plunger is pushed in, which breaks them.
Pushing the plunger in too far against the ratchet merely means the lights never go out!
Depress the pedal, pull the plunger out and let the brake pedal up to reset the plunger to the correct position in that case.
What really want to say is that not everyone has or has access to code readers, and that doesn't mean you can't fix the problem. Random replacement of parts is ultimately successful, even down to replacing the whole car, but is inefficient. One can do better than that.
In general the three amigo scenario seems to involve the ABS system, and having fixed the switch - which has nothing to do with the brakes at all - its merely a pedal senor to lights on device - there remains the issue with abs sensors and here its pretty likely that the problem is something obviously broken on the wheel sensor stiff which is all possible to inspect from underneath.
So wheels off and have a look first. Only if that doesn't resolve the problem should someone who hasn't got a code reader start to think about involving stuff first.
Years ago I was designing a hifi FM radio, At some point a new front end was specified by the customer, and at some future point I re-measured te performance and found it was noisy and it hummed.
The customer insisted on an independent consultant to check my part of the design and see whether I had cocked up. I told him I hadn't, but I hadn't got time right now to prove it to him. He spent a fortnight analysing my design and pronounced it error free. 'I told you it was' 'but you couldn't prove it' 'of course I can' I said, and removed the tuner head and injected the signal in afterwards. No noise, no hum.
The moral is that sometimes there are easier ways that two weeks of calculation or a code reader to zero in on a problem.
(If you are interested the manufacturer - Philips - eventually accepted they had a problem - or two problems with the tuner head. The noise was down to a zener diode stabilising the voltage controlled oscillator. Zeners are very noisy devices until you pop a fat capacitor across them - and the hum was down to the use of a ferrite cored oscillator coil. in close proximity in my design to the mains transformer. They all had to be replaced with brass cored coils).
I am currently chasing a fuel burning heater problem. I suspect my stat is stuck open leading to the FBH coming in when it shouldn't be needed. Now here logic gets me that far, and on an older car I would simply pop the stat housing drop the stat in some hot water with a thermometer and test it. On a TD4 that's a bugger of a job to get to the stat, so its actually cost and time effective to put a code reader in and read the coolant temp.
the pint here being that that
is a case where a visit to someone who can code read makes more sense.
But there is no general answer. I had a pegeot to fix once that would stall when hot. and not restart. I phoned up someone who understood the EFI system and he confirmed my suspicion that it was a water temp sensor. After I had spent £70 in a garage who didn't fix it.
Removal of the sensor revealed that it was not doing a damned thing. So a new one was purchased and fixed the lot.
Code readers aren't the answer to every problem, unless you are a total numpty like most garage mechanics seem to be these days.
