On the run diagnostics with the AESwave Uscope
Being in a hurry all the time means I like to do things as efficiently as possible. This is especially true when my own car breaks down in the middle of the week! We as diagnosticians know this first hand and are always looking for ways to make our diagnostic processes easier and faster.
This vehicle is a 2007 Honda Element with a concern of over heating when sitting in stand still traffic. The vehicle only acts up on really hot days.
I began my diagnostic approach by testing fan operation since the vehicle does not over heat going down the road. I checked scan data to be sure coolant temperature was at a normal operating temperature to make sure I didn't have a skewed ECT sensor and that checked out to be fine. I then decided to check fan operation using the bi-directional controls in the scan tool. At this point I noticed the radiator fan appeared to be turning slow but the condenser fan was running at normal speed. A quick check of the wiring diagram told me that there was only an on or off option not any variable speeds.
The first picture is of my amp clamp on the 60a setting around the 20a radiator fuse. The second is with my amp clamp on the 30a fuse for the condenser fan. The radiator fan waveform not only appears that only one commutator bar is working but also shows around 150mv which is 15 amps. A circuit tends to use roughly half the amperage it is fused for so 15 amps is a bit on the high side for a 20a fused circuit. The reason I chose this test is because of what can be learned without taking anything apart. This test tells us for sure that we do not have a ground problem, a voltage problem or a pin fitment problem. Because amperage is the same at all parts of a circuit which means that each connection is able to flow 15 amps of current through it.
Looking at the patterns we can also see that the radiator fan pattern is much uglier looking compared to the condenser fan. The condenser fan also only had around 65 mv on the waveform which is 6.5A. We can clearly see that all the commutator bars appear to be being used as well.
As long as the circuit is doing work we can use an amp clamp to measure the current passing through the circuit and determine if powers, grounds and all connections are good without having to disconnect anything to test.
Nice post, but I am confused about something. If the current in a series circuit is the same at all points, then a voltage drop will lower the current in the entire circuit. Then the current measured will be lower anywhere you measure it, not different depending on where you measure. Nice catch on the bad fan motor!
That is correct, and if the amperage is then low in a circuit when checking amperage I would then have to test my inputs, grounds and connections. if you had something causing a voltage drop say near the load in the circuit your amperage flowing through the fuse would also be low.