Manager Forum

It's happed twice at my shop in the span of two years. A Honda is in for no a/c. Attach a/c station and look at pressure, finding them borderline we recharge the system and still have nothing. Go to test the pressure switch on the low side and using a Power Probe (love the newer version) check voltage on the plug. It's a three wire sensor power, ground, activation wire. Have power, have ground, power up activation wire like I do on every vehicle with this condition and vehicle just shuts off like it did three days ago. One of my techs reminds me of when it happened to another Honda two years ago, I fried the pcm. Obviously I remembered it just as the car shut down getting a bit aggravated that I didn't listen to the little voice telling me there might be something I should be remembering. A bit too late to be of any help.

My experience has been to never power up the third wire on a three wire sensor, they almost always go to a module and are a sensor voltage, not an activation wire.

Which power probe are you using? The latest one I have at this time is the hook, and I like it except for the size. I still seem to grab my power probe3 most of the time....

Right now I'm using the Power Prove IV. I have all the goodies that go along with it like the short finder and all the extra probes. My biggest problem is I go "old school" to quickly some times and resort to the well known "jump it out" method. Now we all know I'm like this and this issue is also imbedded in the minds of all that work here including the book keepers, accountants, parts suppliers, all the delivery people that are in and out of the shop all day and all the mentalists within a twenty five mile radius of the shop . Heck I have all the diagnostic scan tools, diagnostic equipment, specialty tools, IATN, Direct Hit, Mitchell Forum, World Pac Forum, Toyota, Ford, G.M., tech support sights and I always feel the need to tap everything with a small hammer or ratchet to see if it will straighten out and run well. As soon as it cut out I knew damn well what I did and right away blamed it on the probe. What I would like to have is a tool akin to the Power Probe that will do what the IV does now plus an ohm option as well as an ability to read (precise and to the 100th) voltage and screen out any minor fluctuation. I have an issue of loosing focus if the screen is small and continues to fluctuate. As long as I'm developing a tool to fit my needs I will add a probe that will hook over a wire and read voltage without being pierced and be able to filter out anything else. Years ago a tool guy was selling a test light that could be looped over a wire and you could pull a trigger and it would pierce the wire and tell you if it had power. Back then I would look at the brightness of the bulb and judge the voltage. Yes, about a year or two later I was running into wiring issues where wires were rotting because the probe piercings weren't sealed. I would use either liquid tape or a little dab of gasket goop. Gotta run now have to put a Sprinter back into running condition so it can be used today and taken apart again when the injector shows up. Have a great 4th all and above all please be save and aware of any idiots within your safety zone.

While I understand what's going on, I usually connect my scan tool for AC diagnosis purposes because of potential PCM damage while testing otherwise. Personally, while I have a Power Probe, use it and love it, I do not use it for diagnosing AC or engine electronics for the reason of possibly damaging a PCM or other control module. How do I know I can ruin an otherwise good component? Experience!