- This topic has 3 replies, 2 voices, and was last updated 9 years, 2 months ago by
.
- Topic
Hey guys! This is my first post on the forums, I’ve been watching ETCG since before I was even interested in becoming the mechanic I am now, but now I have an issue that I just cant seem to figure out and I figured I’d go ahead and ask some fellow techs for advice on the situation. We got this 2004 Mazda 6i in with the complaint that if he let the car sit for a while, ran it for a bit, then shut it off he would hear a clicking or humming. So he dropped the car off and we told him we would get to it the next day. The next morning comes around, I go to start it. Dead battery. Great. Go inside and get the jump pack and hook it up, go inside to start the car and before I even put the key in I notice the gauge lights are on and the battery, oil pressure, and check engine indicators are all lit up and the passkey indicator is flashing like crazy. This is all before I put the key in. A bit confused at this point I go ahead and try to start the car, nothing. Try again, nothing. Passkey light still going nuts the whole time and check engine light flashes if I turn key off. So thinking the Passkey system was disabling start up for some reason I turn off the jump pack, go in the car and turn the key all the way on, then turn the jump pack on, now it starts. Weird. But it doesnt end there. I take the car inside and put it in our bay and shut it off. when I shut it off all the gauge lights stayed on but much dimmer than normal, and the passkey light is flashing again and boom, check engine light starts flashing. So weird. Go to start it, wont start. But I can hear a clicking under the relay panel now so I have my boss try to start it while I feel for which relay is clicking when we go to start it, bose relay. That was no help. I go back in the car and try to figure out what is going on when all these gauge lights are staying on. I turn the blinker switch, the blinker starts clicking, with no key. I get out, close the door, and try to lock the doors with the fob. Nothing. I can hear the buzzing and humming the customer was talking about now so I go under the hood to listen for what it is. Its the electronic throttle clicking back and forth. I’m completely confused at this point so I go to check the DTCs. There were two codes, one for losing communication with TCM and I think the other one was for the PCM but I’m not sure at the moment. I pull up the live data to monitor the variables to see if anything looks off. Of course nothing does, so I shut off the key and set the Verus down and try to think for a second, but then I look back down at the screen and its still receiving data like the car had never been turned off even though the key wasn’t even in the ignition. I was just so confused at this point i just decided to see if the wipers still worked too, why not right, click the wiper swich to high, BOOM, everything turns off. Scanner loses connection. Keyfob works. Throttle stops humming. What. I turn the wiper switch off, everything turns back on. Me and my boss decide the switch must be faulty and the way they have everything wired the faulty switch is causing the car to think the ignition is still partially on hence why its still keeping the computer on even after the key is out. We order the new switch and get it the next day, put it in, and what do you know. Everything is fixed. It all works fine, the car turns off when you pull out the key and nothing stays on. But since at this point the battery has died multiple times I decide to check the battery and charging system, so I use our ACDelco tester and the battery is bad, yeah I figured. So i test the alternator too, and it says the alternator is also bad and has excessive ripple. Same result with 5 more tests. The customer decides he will put a new battery in and disregard my recommendation for a new alternator and he just came back in this week saying the car is doing it again. It died, the gauges are all staying on when he pulls the key out, the throttle is still humming, and it all stops if he turns the wipers on high. What do you guys think is going on here? Any advice would be most helpful.
- Replies
I think you are exactly right…a bad battery. Things that can cause weird electrical stuff is bad grounds (unlikely here), low system voltage, and AC ripple. All those symptoms you mentions are just saying low system voltage to me the entire time I was reading your post…some of the statements you made just really point to that, for example…
“gauge lights stayed on but much dimmer than normal
losing communication with TCM
I turn the wiper switch off, everything turns back on
And FINALLY…ACDelco tester and the battery is bad, yeah I figured 🙂
Also you did install a new battery but you said the alternator is bad so that would make sense that this whole thing repeated itself. I personally don’t think it had anything to do with the wiper switch I think it was just coincidence. I think the wiper motor, when on, was pulling system voltage so low that everything was just shutting off.
Computers do all kinds of weird things at low voltage because in order for a voltage regulator to work it’s supply voltage has to be greater (usually by at least 1.5-2.0V) than it’s regulated voltage.
AC ripple really affects DC electronics as well. That guy really needs to let you retest the battery and make sure it is still good then put in a new alternator.See I would normally agree with you but on the times where I didn’t have the key in and the gauges were all dim, if I turned on the headlights the headlights would fully illuminate and the gauges would get fully bright, and if I turned the wiper switch to high the gauges would all turn off and the buzzer would go off like normal if you left your headlights on after you turned off your car. So I don’t think the wipers were pulling too much voltage. I’m really at a loss on this.
Sent from my iPhone using Tapatalk
- You must be logged in to reply to this topic.