Wide Open Throttle.(WOT)
11-11-2018, 06:39 PM
#1
Wide Open Throttle.(WOT)
I have a curious issue with my 2005 F150, 4.2 V6. At wide open throttle(WOT) all of my instrumentation, speedometer, gauges, idiot lights, etc... Drops completely offline.(stops working) My AC/Heat fan motor does as well. The lights continue to work without even a flicker, and my engine doesn't miss a beat. It is almost like I am doing a test sweep of the gauges. As soon as I get out of the gas, everything comes back online. This is the only time it happens. Has anyone ever experienced this issue? Thanks!
11-12-2018, 08:24 AM
#2
Mark
iTrader: (1)
I would suspect a voltage regulator issue in the alternator.
11-12-2018, 09:21 AM
#3
I thought the same thing, but my alternator just failed, and it was replaced with a new one. I had/have the same condition with both alternators. Have also have a brand new 850cca battery.
11-12-2018, 12:27 PM
#4
Mark
iTrader: (1)
What brand alt did you install ?
11-12-2018, 03:20 PM
#6
Mark
iTrader: (1)
I’m no telling you to swap it out but, our trucks are very picky about the voltage regulator inside the alt.. I will always recommend a motorcraft re-man for that reason. It’s the only thing that makes sense with your problem.. if it was just the cluster and not the HVAC too.. I would suggest troubleshooting the cluster.
11-12-2018, 04:54 PM
#7
Yeah, I don’t disagree with you. You may be spot on. The only thing that makes me doubt the alternator, is the problem was happening with the old one installed, probably about two years earlier. I do take it fairly easy on my truck, so don’t put my foot in it often, but when I do that happens every time. It could be the previous alternator had degraded to the point that allowed the condition to happen. And my replacement alternator was junk off the shelf. That is a possibility. Was thinking it could be the throttle position sensor too.
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01-27-2019, 06:02 PM
#8
Hey Mark,
You was spot on with your diagnosis. It was the integrated voltage regulator in my remanufactured alternator. Wanted to come back and report my findings in case someone else has the same issue... Installed my OBD II diagnostic tool the other day, and selected voltage. The voltage was a steady 14.2 volts, that is until about 3800-4000 rpm. Then it would abruptly spike to 20+ volts. This is when all accessories, speedometer, gauges, heater/A/C, etc... would drop off line completely. I believe this to be an overvoltage function of the ECU to prevent damage. Replaced alternator, and everything is back to normal. Thanks for your feedback!
You was spot on with your diagnosis. It was the integrated voltage regulator in my remanufactured alternator. Wanted to come back and report my findings in case someone else has the same issue... Installed my OBD II diagnostic tool the other day, and selected voltage. The voltage was a steady 14.2 volts, that is until about 3800-4000 rpm. Then it would abruptly spike to 20+ volts. This is when all accessories, speedometer, gauges, heater/A/C, etc... would drop off line completely. I believe this to be an overvoltage function of the ECU to prevent damage. Replaced alternator, and everything is back to normal. Thanks for your feedback!
01-28-2019, 05:39 AM
#9
Mark
iTrader: (1)
Sweet.. glad you got her fixed.
01-28-2019, 07:29 AM
#10
Senior Member
Thanks for the update with the fix, wish more people did that.