Community Forums

clifford j · 02-20-2016, 04:52 PM

Question about voltage drop. It sounds like your testing the voltage while there is current flowing to the RV brake magnets. The blue whire is the conductor supplying the power. How do you know that the Ground is good (white wire) to chassis. . How do you know 10 volts is bad.

CLIFF

dayle1 · 02-20-2016, 05:14 PM

Quote:

Originally Posted by clifford j

Question about voltage drop. It sounds like your testing the voltage while there is current flowing to the RV brake magnets. The blue whire is the conductor supplying the power. How do you know that the Ground is good (white wire) to chassis. . How do you know 10 volts is bad.

CLIFF

I agree, 4 magnets should draw about 12 amps and given wire gauge, wire length and contact resistance thru several connectors, having just 10 volts under load can be perfectly OK depending on where the measurement is being taken. A pull test is justified, preferably on gravel and seeing which wheels lock up and which ones continue rolling.

Old-Biscuit · 02-20-2016, 06:37 PM

IF you are going to pull the pin out of the of the Emergency Breakaway Switch unplug the trailer umbilical cord

With pin removed FULL trailer battery voltage will be applied and can backfed thru umbilical cord to brake controller in truck. Some are OK but some controllers have burnt out from the backfed'

clifford j · 02-20-2016, 10:24 PM

Good suggestion Old Biscuit, some don't have a diode (one way valve) for protection.

CLIFF

TheOldMan76 · 02-21-2016, 05:12 AM

Yes I'm, testing under load. with magnets energized. Conversations with techs @ both e-trailer and Tekinsha indicated that even under load, the potential at the brake magnets should still be about 12v. I redid everything in the camper, right down to grounding each magnet at the frame, and redoing all connections on the main chassis ground, from the frame back to the batteries and hitch. I'm also experiencing some other electrical probs (intermittent horn, inop cruise control, varying fuel gauge etc.), that I think all go through the C205 connector. I'll work on it again this week. I don't think I've properly expressed my thanks for all the help and suggestions, but I really do appreciate you guys and all your advice. TOM

dayle1 · 02-21-2016, 05:53 AM

Quote:

Originally Posted by TheOldMan76

Yes I'm, testing under load. with magnets energized. Conversations with techs @ both e-trailer and Tekinsha indicated that even under load, the potential at the brake magnets should still be about 12v. I redid everything in the camper, right down to grounding each magnet at the frame, and redoing all connections on the main chassis ground, from the frame back to the batteries and hitch. I'm also experiencing some other electrical probs (intermittent horn, inop cruise control, varying fuel gauge etc.), that I think all go through the C205 connector. I'll work on it again this week. I don't think I've properly expressed my thanks for all the help and suggestions, but I really do appreciate you guys and all your advice. TOM

We are probably being a little loose with the term '12V' since actual battery voltage with a fully charged battery is higher. With that said, even the controller will drop some voltage, most use switching transistors so there will be about 0.6V drop for them, then if the controller has a protection diode as well, that will be another 0.6V drop. So, under full load and in spite of what the techs claim, I would expect best case voltage at the magnet to be 1.5 to 2 volts less than the voltage measured directly at the battery. Also, since most brake controllers do use switching transistors to 'chop' the DC voltage, some meters do a better job of measuring the average voltage of this signal than others.

clifford j · 02-21-2016, 06:00 AM

@ the OLD MAN, we know you appreciate the help, we're happy to help.
You said bulkhead connector C205 , I looked back and couldn't find where you told us what truck ,model and year.

CLIFF

TheOldMan76 · 02-21-2016, 10:09 AM

I decided to hook her up & try the brakes again, maybe 10v is enough. I'm using a pretty good Fluke DVM for testing. I think I must have some parasitic drain, not enough batteries to start just now. Could be from all this testing I guess. got the battery charger on it, I'll give it an hour and see if it fires. 2000 F350 7.3 CC Dually. Teknosha controller. Looking at the firewall, on the inside there is a black covered box that wires all go into. Outside, other side of box, with wires exiting into 4 square plugs, bolted to fender well. I think the black box maybe just a conduit thru the firewall. All 4 of the square plugs are pretty well covered with road grime.

wingnut60 · 02-21-2016, 10:35 AM

A lot of the problems mentioned may well be due to the truck batteries--need to have them in good shape and charged well, or the alternator may not be enough to do all the work needed...

shovelhead86 · 02-21-2016, 05:09 PM

I looked up the user instructions for my Reese 1800# Elite hitch. It says the hitch has to be open. I can see the way it is designed that there is no way the king pin could enter without breaking something.

TheOldMan76 · 02-23-2016, 05:31 AM

I guess I have caused this thread to wander all over the place. Thought I'd give a little update. I took the unit out on the local loop road, about 4 miles and engaged the brakes 10 or twelve times, slowing from 30 or 40 to twenty, and although I can feel some drag, I wouldn't be comfortable taking it out on the interstate. I still only have 10 volts max at the brakes. Visited the local all around trailer supplier yesterday. He hemmed and hawed and admitted they weren't truck mechanics, but looked at a lot of brake problems, bring the truck and trailer and they'd look it over for $90/hr. Went to the local Ford dealer trying to get some info on the wiring, and I must say they really tried to find something on their computers, but finally said "it's just too old"! But they had a tech that was really good on wiring, and did all their diesel work, and bring it in @$125/hr. Guess I'll bite the bullet and buy the 3 cd set of service/wiring manuals on e-bay and see if I can dope it out myself.

tinkerreknit · 02-23-2016, 06:25 AM

I'm unable to remember the name of the forum (maybe PowerStrokeNation), but I quickly got answers to various questions I had about my truck. I also read through some of the other topics and it seems there are a lot of knowledgeable guys out there with technical answers.
I hope you get fixed up. I've learned much from this thread.

wingnut60 · 02-23-2016, 06:57 AM

Take it to a TRAILER repair shop--not an RV shop. Ford dealers can't tell you much more than either "the light box is working"----the truck you have isn't really set up for computer analysis, but if it was, they would tell you "the brake controller is working correctly." Been there, done that. You rarely would get a problem like you have fixed at a Ford shop--to them, its always "in the trailer."
Have you done the e-brake test yet? Have you put an ampmeter in line with the brakes when applying them?
Joe

clifford j · 02-23-2016, 12:12 PM

I looked at the wiring diagrams today on Snap-on's Shop Key service . I used 2000 F350 Super Cab. I see that fuse # 28 supplys the power on a red wire to the under dash location. At the same location the factory included a blue brake wire that goes to the rear bumper area. The diagram did not show any components like connectors in that blue wire. I didn't see a bulkhead connector block. I did see there is a relay for the 12 volt power supply the trailer.
Men at the shop talked about all the things we discussed here, such as, ensure grounds are good, pigtail connector contacts are clean, do a load test with an amp meter,make sure the controller is set at max, not electrical but be positive the brakes are in perfect working order and functioning properly. No rust on magnetic drum surface. Getting back to an earlier suggestion,,,each magnet should draw at least 3 amps at full load X 4 = 12 amps. Your Fluke meter has an amp mode. ( amp feature is a series connection with the load. So, start the engine so voltage is up to 13 to 14 and do your testing.
Not much more can be added.

CLIFF