Wiring In Your Vehicle


                  The wires in your vehicle, can fill a small room. Probably strengh for miles end to end. I'm not sure, but I can tell you, that there is a lot of wire in a vehicle now days compaired to just 30 years ago. I'll show you a wiring diagram for a 1967 Chevy truck and one from a 2010 Chevy truck.


Notice the 67 wiring harness includes the head lights ,ac, alternator, horns, front bleakers, and the engine. The 2010 wiring harness is for only the engine, no lights, ac, alternator, horns, just engine. Now take into account that on the 2010 there is still the rest of the components that are in a 2010 truck, like BCM (body control module),that takes care of the lights, windows, stereo, ac and some of those things that the BCM controls have there own modules. Let me see if I can give you a few examples, PCM (power control module),TCM (transmission control module),HVACM (heater, ac control module)SCM (suspension control module)LCM (lighting control module)DCM (door control module),some modules have the same abbreviations, such as ECM can mean engine control module or electronics control module. Another one is TCM, can mean transmission control module or tailgate control module, depends on what kind of vehicle your working on.
         There are so many things that can go wrong with not just the wiring in a vehicle, but the sensors, modules, window motors, door locks, heater/ac components, anti lock brakes, air bag systems and so much more. The diagnostics of the wiring system can be as easy as finding a burned fuse are as hard as trying to find a broken wire in a harness with 30 wires running thru it. Where does one start to find a problem in the wiring, it depends on what kind of problem your having. But it also has to do with the tools you will need to find and fix your wiring problems.

                                             Oh Where, Oh Where, Do We Start

          There are so many things that can go wrong, I really don't know where to start to tell you how to fix your problem without knowing what your problem is. Let me say that you will need a good test light to fix most wiring problems. You will need a voltage meter, some jumper wires with alligator clips on the ends, some paper clips that you can straighten and bend to use for small jumpers. Sometimes your going to need a wiring diagram of what ever your working on. A owners manuel for fuse locations.

                                         So How Do You Use These Tools
          Lets start with the test light 



Some people think that a test light is only used to see if your getting voltage to something. You can use the test light to see if you have a ground to somethings. You do this by hooking the clip to the positive post of the battery and toughing the block, or probing a slot of a plugin to see if you have a ground. You can take a paper clip and straighting out one loop of the clip, insert it into a fuse slot, hook your clip of your test light to the paper clip and probe something under the dash to see if you have a good ground. Say you have a heater blower motor not working, how do you know if its a bad motor or your not getting voltage to it. Well you unplug the blower motor, turn key on, ground your test light and probe both wires going to the blower motor. One wire should have voltage going to it and light up the test light. If the test light lights you know your getting voltage to the blower motor, now take your paper clip and put it in the end of your test light, put it in the plugin of the blower motor and the other end of the test light into the other slot of the blower motor plugin, and if you have a good ground the light should light up. If test light comes on you have a bad blower motor. If the light does not come on you have a bad ground. That's a few ways to use the test light.


                             Voltage Meter


        It's not just a voltage meter, it's a continuity tester, you say what the heck is that. Well lets say you want to find out if a wire is good all the way thru. You take your volt meter and put it on the ohms reading, any setting in ohms, take the volt meter probes and tough each end of the wire and the meter should read 000 if it is a good wire. If wire is broken somewhere in the line the meter will read "I  ." . On the ACV settings you can check some of the sensors, such as crankshaft sensors, speed sensors,o2 sensors, any sensor or that puts out a ac voltage. Those sensors are called ac generators,they will put out anywhere from .01 to 1.5 ac volts and sometimes more. Take the o2 sensor it's a heat voltage generator, the more heat you apply to it, the more volts it puts out. Some of these sensors are call magnetic pick up sensors, those are the ac generators. Some of these sensors are called hall effect sensors, these sensors put out a signal from a voltage source.They need a voltage source to put out a signal, unlike a magnetic pick up which produces a voltage or signal from itself. Hall effect sensors are checked by using the DCV settings on the meter and sometimes using a test light.


                      Jumper Wires/Paper Clips​

               Jumper wires are used for a lot of testing in the wiring systems. You can use them to check fan motors, ac compressor clutchs, to hot wiring a vehicle to start it. You can use them to power up things like power window motors in doors, to check head lights, to powering up things you want to install on your vehicle, like stereos, fog lights even electric seats. Let me give you a example of using a jumper wire to check a radiator fan motor. Find the coolant fan relay, pull it out. Now get your test light and turn key on, with test light hooked to a ground, probe the slots the relay plugged into. The test light should light up on 2 of the slots. Remember these 2 slots, you don't want to stick anything in those 2 slots. That means 2 slots are left,1 goes to the fan motor, take your jumper wire and hook 1 end to the battery positive post, and with a paper clip straighten out,hook to the other end of your jumper wire. Now probe the other 2 slots, making sure key is off, when you insert the clip into 1 of the slots the fan should come on if fan motor is good.

​If you have any questions about a wiring problem you have, e-mail me or go to the forum section.