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tow haul flashing during AC recharge/operation

955 views 4 replies 3 participants last post by  lmorgan 
#1 ·
I was recharging my AC system and noticed as soon as I opened the gauge on the freon, my tow haul light started blinking. It kept this up during the duration of the recharge. If I switch the AC to heat, the tow haul light immediately goes off. If I turn the AC back on, the light comes on and starts flashing. The vehicle is NOT in motion or in gear when this happens. If I turn off the AC and kill the truck, the light stays off when I restart until I turn the AC back on.

Without the AC, the truck runs and shifts out fine. The tow haul works fine as well. I got a little worried and didn't finish charging the system. There is no CEL or warning lights on and gauges seem fine.
 
#3 ·
I don't know how to begin to look for a short. I haven't done any work under the dash or in the column, but I did recently do an engine swap. One thing I noticed this afternoon is that after I start the truck and let it idle, when I turn on the AC the rps jump up somewhat on their own and the tow haul light comes on steady for a moment, then starts blinking. It will keep this up until I either kill the engine or turn the AC to heat. I'm really confused on this one. I've checked the archives, but I'm not finding much about the tow haul light except that when it flashes, it is usually a tranny sensor.
 
#5 ·
I don't have a scan tool for this truck, but I'm going to take it to the shop as soon as I can get it in and let them scan it and pull a vacuum on the AC system and see if they can figure out the issue. I just did a complete engine bullet proof and replacement, I'm just exhausted at doing the work myself. I'm going to bite the bullet and let somebody have the headache of working on it for a change. I'll keep you guys posted on what the issue was.
 
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