TOW/HAUL, Battery lights makes for long drive

[epa1775]

Driving back from Yellowstone to SLC today I was towing a 22 ft camping trailer back home. The first 120 miles of the trip went fine. Accelerated and slowed down fine except the brake box wasn't working as well when I drove up on Monday. (Seemed as if when I hit the brake pedal the brakes on the trailer were't engaging. The manual brake lever didn't seem to slow anything down either.)

After stopping for lunch and refueling we started hitting the hill portion of the trip. I had been using the TOW/HAUL function going up and down the hills and switching it off on the flats. Coming down off the hill and onto a flat the message center illuminated with the battery. The battery meter read under halfway. I switched the TOW/HAUL off and the truck then started functioning normal. This happened several more times for about 10 mile. For about 10 miles it also seemed like the truck was stuck in TOW/HAUL mode when I had turned it off. For a while I couldn't go over 60 mph. The TOW/HAUL mode also ceased working. The truck never ran hot in regards to the engine or tranny.

The only other thing I can think of is on Monday the tranny got up to about 200 degrees once and then cooled off. I also smelled something burning but not sure if it was me or the vehicle in front of me. Smell lasted 30-45 seconds.

I'm taking it in first thing tomorrow morning. I'm already going to be charged at least $85 for the diagnostic test. Any one know what other damage I'm looking at? I check the tranny fluid every fuel up and it seemed normal.

Thanks for the help in advance.

Pete

[AKMark]

Almost sounds like a battery connection problem. If a battery connection is loose, it can cause all sorts of bad things to happen. Same if it's corroded. I would start there and see verify those first. Tow/haul shouldn't cut your voltage down like that, unless there's a short somewhere.

200 isn't that bad, shouldn't have hurt nothing, unless something shorted out, which would explain the burning. Pull the trans dipstick and verify that your fluid is red and not burnt, also check the fluid level.

[jbplock]

Just a guess based on the symptoms in your post but it sounds like your trailer brakes stopped working (as AkMark said) and so the truck brakes and tranny were taking the full brake load of the trailer on the hills maybe causing the tranny to go into limp mode ?? .. the burning smell you noticed could also have been your brakes .. do you have a way of reading and codes that may have been set? If not AutoZone will usually read codes for no charge ..

[epa1775]

Thanks for the help.

Battery connectors are good. No corrosion or looseness. Seems like your right about the trailer brakes not working. The trailer's a rental so I really don't have a way of verifying if the brake system on it went out. I'll take it to Autozone or the dealer. I'll keep you posted on the diagnosis.

Pete

[Mark Rinker]

My guess is your hot smell would be brake pads/rotors trying to stop the load behind you without any assistance.

Further, and significantly compounding the problem is the oversized tires on your rig, without oversized brakes. Consider the additional pad to rotor pressure and resulting heat required to slow both truck and camper, when the wheel/tire diameter is increased.

As for your voltage fluctuation, you may have one battery with a bad cell, and/or an alternator about to go out. High underhood temps related to towing often put the final touches on batteries and alternators. Also consider the extra lights and electrical load from the trailer - if you have issues with the braking system you might have a constant draw from one or more of the electromagnets that engage the brakes.

I see on another thread that you were working on trailer wiring. Be careful, you have 12V+ constant in that group, along with 12V+ for brakes, turns, and running lights. If you wire any of these to your trailer brake circuit, you can have LOCKED trailer brakes when you least expect it...don't ask how I know these things...