What is a "real life" pretrip?

a "real life" pre-trip is only as good as the one you do. Some do the bare minimums and others look in every nook. I've seen quite a few people just walk around and check the exterior. Few others like my self look under trailers.

Since I've been doing local flat bed p/u's for out of town runs, I generally tend to take an extensive look at the trailers I'm getting told to hook up to. In 3 weeks I've already had 3 running lights replaced, uneven wear flat spotting on tires (spread axle) one trailer had 3 shocks that were rusting pretty good (holes in the center) . I've caught one of the cotter key's missing on the slack adjuster pin, the pin was working its way out from the slack adjuster.

I could go on but it really varies.

 

What do we get *when* your guarantee fails?

I guess I should rewire my truck so when I hit the 4-ways, the headlights flash...

(oh, and if you ever drove the older style trucks or pickups or cars, you would remember that the emergency flasher control was often part of the turn signal lever, and that was because it activates the same wires.)

 

I have sit in too many truckstops having my morning coffee and watched drivers. I'm not kidding here. The average pretrip is a walk around the rig with the headlights and flashers on. No looking under the trailer for leaks. If it don't stand clearly out it is assumed it is OK. I have been in this business too many years and watched maybe a thousand or more post/pre trips. I admit I've did it. It is a VERY rare driver that does a proper inspection of their rig no matter if it is post or pre everyday, it just don't happen. After a while you learn to check the legals and tires on picked up trailers. This is why you see so many dang one eyed monsters every night. (If you don't know what a one eyed monster is ask your safety man).

 

I once asked a mechanic about flashers. I was told and am under the understanding that flashers work by closing all of the turn signal circuits. Since I am not a mechanic I will just say in my career I always used my 4 way flashers to check this. I'm not going to look for it, but I think a diagram of all the circuits in the pigtail going from the tractor to the trailer should give you your answer.

 

While their are some vehicles that have seperate control circuits or seperate flasher relays for the 4 ways, as a mechanic or a driver, I have never seen any production vehicle with 4 way flashers using separate bulbs from the turn signals.
(and usually you are right, and it just powers both sides at the same time with the same circuits.)

What this means is that every vehicle I have ever tested the lights on (which is most of the vehicles I have ever driven lol ), hitting the 4 way flashers will test all your turn signal bulbs.

The only problem is when something is wired wrong, so left is right, and this won't tell you that.
This usually is a trailer issue, so usually I will check the turn signals to verify dyslexia when I am testing a new trailer. If it is dark, or there is something behind the trailer, I sometimes can do that from the cab, just to make sure the right side is flashing, then I hit the 4 ways to check all the bulbs.