greg92jeepxj
Official Supporter
Here is something I would like to stress to everyone with regards to electrical diagnostics. By no means am I a technician or ASE certified but I do have an understanding for as many members and non-members do for diagnostic testing . Despite our best efforts to diagnose faults , no,starts or otherwise , we must use safe equipment when we wish to test /diagnose electrical or computer circuits . I stress COMPUTER SAFE every now and then and it is something that is sometimes hard learned by us. If we are not in possession of a proper wiring diagram as we should be , we may be at risk of causing an electrical,over draw on a computer driven or monitored circuit. For example : a PCM typically feeds a sensor at about 5 volts reference beside its signal reference. A 12 volt test light applied to either circuit will cause damage due to over draw. Hence the reason for COMPUTER SAFE test lights and volt/ohms meters. A test light marked COMPUTER SAFE will have a diode rather than a light bulb . A diode draws approximately 1/4 of a volt . A test light draws 12 volts. You DO NOT want to attempt to read a circuit that may be a feedback line to,or from the PCM with 12 volts ! Trying to draw 12 volts,from a circuit that is meant to supply 5 volts or read a little 1 volt or less spells TOAST ! Conversely , a digital meter that is of 10 mega ohms impediance is compliant and computer safe. It draws the least voltage to obtain a reading to its digital,scale. A cheap digital meter such as ones obtained from harbor freight for $7 or less are NOT compliant . It has been stressed enough times that wiring harness found in our jeeps or any vehicle we drive may have wires gauged at 18 or thinner . It won't take much to draw too much current voltage and cause overheat to wiring or the devise on one end or the other , namely a PCM , BCM or other sensitive electrical devices. Granted , some or most compliant dvm's are $$ , compliant test lights generally aren't but much cheaper than a PCM , BCM ( body control module ) or other devices . Not to mention wiring harness damage unseen ! Let's,take,the precaution and obtain such equipment if we are going to do,our own diagnostics to,avoid being sorry and costing untold labor expense .
