Posted 2005-08-28 9:08 AM (#29676) Subject: Blowing fuses
Member
Posts: 11
Fellow haulers,
I have a trailer, 95 SUndowner bumper pull, that I bought about 6 months ago. Suddenly, I am blowing fuses in the Tahoe wheni plug in the trailer.
Any advice on tracking down the problem? Are there any electrical measurements that I can make on the trailer plug? Is there a chance this is a problem with my 97 Tahoe? It does blow fuses occasionally, but this problem just started happening.
Posted 2005-08-28 9:18 AM (#29678 - in reply to #29676) Subject: RE: Blowing fuses
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Posts: 171 Location: Henderson, TN 38340
We need more information! What fuse blow's? Is it always the same? Does it blow instantly as you plug it in, or do you have to do something like step on the brake pedal?
Posted 2005-08-28 1:36 PM (#29683 - in reply to #29676) Subject: RE: Blowing fuses
Expert
Posts: 2689
Originally written by Bgdddyrch on 2005-08-28 9:08 AM
Fellow haulers,
I have a trailer, 95 SUndowner bumper pull, that I bought about 6 months ago. Suddenly, I am blowing fuses in the Tahoe wheni plug in the trailer.
Any advice on tracking down the problem? Are there any electrical measurements that I can make on the trailer plug? Is there a chance this is a problem with my 97 Tahoe? It does blow fuses occasionally, but this problem just started happening.
I'd buzz the line that the fuse blows on, then do the arithmetic.
v=ir or somesuch. If you don't have a multi-meter, but DO have a horse trailer... a small investment at radio shack, I'm SURE you'll find a future use for it (-:
Posted 2005-08-28 2:05 PM (#29685 - in reply to #29683) Subject: RE: Blowing fuses
Member
Posts: 11
I do have a meter and I can buzz the line, but I already know the amperage is too high. How does that help find the problem?
What I was wondering was do you guys have any insight into fuse blowing problems with horse trailers? Is there a common problem that I should be looking for?
Posted 2005-08-28 2:19 PM (#29686 - in reply to #29678) Subject: RE: Blowing fuses
Member
Posts: 11
Turfa, the fuse was blowing as soon as the headlights were turned on. The fuse was labeled parking LPS and included the gauge lights on the dashboard. This afternoon, I removed all the running lights and tail lights, turned on the headlights and re-inserted everything one at at a time. Everything worked for some reason. SO then I started the engine and the fuse blew. I did the exact same thing and everything worked again, and now the whole thing seems to be working.
One of the running lights was 1/3 full of water. I drilled a hole in the bottom and drained the water. Maybe I put it back too soon the first time and it dried out by the end. I can't explain why it is working.
Most of the There are 11 running lights each with 2 bulbs. Only a couple of them have both bulbs working. I suppose I will have to order replacement lights. I would expect blown bulbs to be opens and therefore not contribute to the fuse problem. Is there anyway that the blown bulbs could be the problem?
Posted 2005-08-28 9:37 PM (#29695 - in reply to #29676) Subject: RE: Blowing fuses
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Posts: 23
You said the tow vehicle blows fuses "anyway" and by that I assume you mean all on its own w/o any trailer plugged in. If this is the case then you need to get that sorted out first. Don't try to troubleshoot two problems (Tahoe+trailer) on one circuit at once or you will drive yourself effing insane. If you want to measure the current draw of the trailer lights, hook them up to a fully-charged 12V battery with an inline fuse in the circuit. The fuse should be rated only very slightly above the combined current draw of all working lamps (go the marking-light mfr's web site for wattage specs, then convert to current with Ohm's law); put an analog ammeter in series if you feel like doing that (watch your polarity and scale). Have someone do the tap & wiggle on the wiring & lights throughout the trailer while you watch the ammeter. HOWEVER... my wild-ass guess is that you have crudded-up/splayed/shorted/damaged wiring in the Tahoe that is causing the lighting circuit to run near fused capacity w/o any external load (based on the Tahoe "blowing fuses occasionally" which I take to mean "all on its own" since you distinguish those events from what happens when you plug the trailer in). Quick test for that: snip the wire for the trailer lights at the very point it connects to the Tahoe's factory wiring; if the "blowing fuses occasionally" problem disappears, then you have solved at least part of the dilemma; now, assuming the Tahoe lighting circuit is actually *designed* to handle your trailer's total light capacity, disconnect the trailer end of that wire from the connector and run a new properly-gauged wire from the snip point back to the connector. As you route the wire pay attention to where it might become abraded over time, and avoid those places. Consider using wire with insulation suited to rough service; I generally use Teflon insulation where this is required. Or if you use PVC-insulated wire then consider running it within flexible conduit for protection. Hope this helps. KS.
Posted 2005-08-28 10:27 PM (#29698 - in reply to #29683) Subject: RE: Blowing fuses
Expert
Posts: 2689
If the tow vehicle habitually blows fuses then fix that first.
At a guess you have an intermittent short to ground SOMEWHERE, most likely in the tow vehicle if it can do it all on its own.
I guess I assumed the fuse in question is a running or brake/turn signal fuse, if so then you're down to maybe 3 possibilities.
There is nothing special about the electrical system on horse trailers - there used to be, but that was when the wiring was insulated with rubber and ran under wooden floors, the urine rotted the rubber coating off the wire. Before my time, but I read about it.
Another possibility that can lead to high currents in LOTS of places, is that the tow vehicle's voltage regulator is bad, leading to high voltage.
I think somewhere you said that the fuses blow when you started the engine.
Try the truck forums for the make/model/year of the tow vehicle.
The VR is almost certainly a part of the alternator... some small number of hundreds of bux should get it fixed.
Posted 2005-08-29 9:39 AM (#29710 - in reply to #29698) Subject: RE: Blowing fuses
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Posts: 11
KelanSasu,
Thanks for the reply. I feel stupid, but it turns out the Tahoe problem IS caused by the trailer. We use the Tahoe 90% of the time to pull the horse trailer, so it is usually a couple weeks in between uses. I drive it for fun (killer stereo) and the wife pulls the trailer. So whenever I drive it and the fuse was blown I did not relate it to the traler blosing problem. I just assumed there was a problem with the truck. I marked the fuse that was blowing so I could work on it later and bingo, its the same fuse. The brake lights and turn signals work with the fuse blown so if my wife drove the truck during the day and out of habit turned on the headlights, she did not even realize that the fuse was blown.
We are replacing all the running lights that have blown bulbs today.
The dealer said that it is not uncommon for a trailer with lots of lights to cause problems in the tow vehicle and we may need to install a trailer light conversion kit. I have never heard of one of those but we may give it a try.
Posted 2005-08-31 7:34 AM (#29814 - in reply to #29676) Subject: RE: Blowing fuses
Member
Posts: 11
Guys, thanks for your posts. I finally fixed the problem.
When I started there were so many running lights that had bulbs out that I assumed the problem was in one of those lights, after removing all the tail lights and running lights and replacing them one at a time, I couldn't find a problem. Sometimes it would work for quite a while before blowing the fuse again.
I took some measurements att he trailer plug trying to find a short from ground to one of the lights. What I found was that the ground was not shorted to the frame. The trailer is 10 years old so I figured I was not getting good contact with my probe. I got under the trailer and the ground was run to an O connector inserted between a conduit box and its cover. The conduit box had all the trailer plug connections. I didin't like that very much so I got the Dremel out and cleaned a bare spot on the undercarriage frame and used a self-tapping screw to get a good ground.
I still had a flaky continuity reading from the plug to the frame and even when I measured from the plug straight to the ground screw. Obviously, My plug was all F***** up. all the little set screws and wires were rusty and "bingo" the ground waire int eh plug had come lose and if you held the plug just right you got contact but if you bent it another way it laid on the 12V post.
Blowing fuses
