Bosch Automotive Electronics





Today I'll show you some simple techniques on how to diagnose a defective air conditioning circuit I'll, also teach you how to determine if a component is failing before it causes a breakdown and leaves you stranded I'll. Show you how to use the power probe hooks power plus mode and what a time-saver smart tip advantage technology can be. We will use the hook to test the complete circuit at the relay terminals and then determine the health of the fan, motor wiring, AC controller and the engine control module driver. We will also use the power probe hooks built-in relay and continuity tester to test for intermittent relay operation. At the end of this video, we will have determined the reason our 2007 honda elements, condenser fan at times, quit working all of these techniques can be applied to any automotive circuit to more accurately diagnose and avoid wasting time or replacing unnecessary parts. Our vehicles, air conditioner at times, does not blow cold.


We've done our preliminary checks and have determined the condenser fan at times will not operate. This causes lack of cooling at the condenser resulting in higher than normal temperatures inside the vehicle when the AC is on. As we look at the schematic, we see that when the AC switch is pressed on, it sends a command to the power control module to ground the radiator fan and condenser fan relays. These relays are powered by three different fuses: a 10 amp fuse under the dash. When the ignition is on and two fuses under the hood in the relay box, one 30 amp fuse for the condenser fan relay and one 20 amp fuse for the radiator fan. Since the condenser fan is intermittent, we suspect the condenser fan relay or the condenser fan motor as being the cause. We will access the complete circuit at the relay terminals to determine the exact problem using the power probe hook. Let'S start by connecting the power Pro hook to the vehicle's battery for easy access to the circuit, we will remove the probe tip and install the three-foot lead with the back probe. Adapter now locate the vehicle's relay box, which is under the hood on this vehicle.


Remove the cover to expose the relays flying the relay that controls the condenser fan and remove it we'll also remove the radiator fan relay. This will keep the radiator fan from operating during testing. Condenser fan relay saket terminal number one supplies power to the fan motor when the relay is energized. Let'S test this now set the hooks circuit breaker setting to match the fuse rating for this circuit, which is a 30 amp fuse for the condenser fan probe terminal number. One the hook will instantly display the resistance of the fan motor. This reading tells us that there is resistance through the fan motor and our fan motor is not open or shorted. Next use the hook to supply battery power to the condenser fan by simply pushing the plus button on the hooks keypad. The fan turns on and the hooks display is showing approximately 6 amps and 1.8 ohms. All on the same screen now put the hook in power mode. This will capture the inrush current and measure and display the minimum and maximum current draw capturing. The inrush current and the stabilized current can help determine the condition of a component high current here could indicate a faulty fan motor. This is one of many valuable features built into the hook. It shows you current. I am calculated resistance. Maximum and minimum current draw in real time as a rule of thumb. Continuous current should not exceed 75 percent of the fuses rated value. This accommodates momentary, current surges and avoids the fuse blowing prematurely, since our fan is pulling six amps and the manufacturers fuse rating. For this circuit is 30 amps. Our fan motor is well within specifications. Our inrush max current is also well within specifications. This test just eliminated the wiring to the fan motor, the fan motor itself and the fan motor ground now put the hook back into hook mode. So we can take advantage of the smart chip. The smart tip advantage automatically selects the right meter for the right circuit conditions, no need to select volt or ohm meter. The hook will do this. Automatically terminal 2 should have battery power supplied by the 30 amp fuse and terminal 4 should also have battery power when the key is on. This is supplied by the 10 amp fuse, let's test them.



Next, we have battery power at terminal 2 and, with the key on, we also have battery power at terminal 4. This confirms the fuse and the wiring are good up to this point. Next, let's test relay terminal number 3, when the AC switch is pressed on, it sends a command to the engine, control module to ground the condenser fan relay and the radiator fan relay. Let'S test to see if this is working now probe the condenser relay terminal number 3, then push the AC control switch to the on position. The hook shows ground indicated by the green LED now push the AC switch in the off position. The hooks green LED turns off at this point. We have determined the condenser fan is good, all the fuses are good and computer AC controller and wiring are good next, we'll test the relay. The hook has a built into channel continuity, tester for testing relays and electrical switches. Let'S test the relay now insert the three wire plug into the hooks continuity jack and attach the alligator clips to the relay terminals. As shown, black connects to terminal number. One red connects to terminal number two. The hooks auxiliary ground connects to terminal number three. The hooks tip connects to terminal number four leave the green alligator clip off. This is used when testing five terminal relays now press the plus button and the red LED should light and the relay should click indicating the relay is working. You should also see the current and resistance displayed on the screen. Next, let's put the hook switch into pulse mode. This will test the relay for an intermittent problem, as we suspect we may have here. Latch mode holds power on constantly and pulse mode cycles, power on for a half second, and then offer a half second continuously. This is how we'll test for an intermittent relay problem. After a few minutes of cycling, the relay on and off, we have verified the relay as the problem. We found that at times our relay would not operate in this video. You saw simple diagnostic scenarios using the power bro hook. The hook has many amazing features. It shows resistance, current draw supplies, power, and even tests relays. The hook has many more features which were not covered in this video but can be seen in other hook, videos for more information on the hook, visit power, probe com,

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