So the only possible impact to trailer braking from your vehicle then is the fused power (or the suspension of the laws of inertia of course)? Where does that connect on the truck?

George

 

Most of the trailer brake controllers I've seen also have an input from the brake light switch so that the trailer brakes won't apply unless you're applying the tow vehicle brakes, regardless of inertia.

Which controller do you have?

 

The brake controller is a "Reliance" brand...bought it from U-Haul. I think it does have a wire to the brake switch, even though I don't remember hooking it up.

Anyway: The Blazer did fine pulling the trailer (2800#) 70 miles round trip.

I'm still nervous about the #10 fuse blowing, because it's pretty hard to diagnose exactly what happened. I've done a visual inspection, tugged and twisted the wires and nothing reveals any problem.
I'm wondering if the low/bad battery caused this overload on #10.
After it died and I pulled it over and turned on the flashers, I tried a few times to restart it and the battery seemed weak. I didn't crank it for long (a fuel injected engine shouldn't ever need extended crank time unless something is very wrong). I checked battery voltage and it was about 11.7V. The flashers stopped working within 10 minutes.
A helpful motorist gave me a ride to get a new battery, and after installing it, I tried starting it again with no luck. Flashers worked for the next few hours as we stood in the shade waiting for the tow.
I now know that if I'd checked all the fuses, I'd have found #10 blown and we would have been on our way. We felt really stupid about that. That's a rookie mistake.

Alternator tests good.
Could a low voltage condition cause #10 to overload?
Thanks for all your help!

 

A low voltage on that circuit should not blow a fuse. That would need an inductive load like a motor that is locked up and not turning but overheating.

You could measure the amp draw of each major component on that fuse circuit and see if any of them are near the fuse limit.


George

 

I was afraid of that!
I think I'll start by reading the total draw through that fuse...if it's close to 20A, I'll try to isolate the components...but if it's not close, I'll be looking for an intermittent short.

Thanks, George.

 

Thats a good plan.

George