Chassis/frame grounding on 12 volt syst on a Scamp 13í deluxe - Fiberglass RV
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Old 03-07-2021, 02:05 PM   #1
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Name: Joseph
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Chassis/frame grounding on 12 volt syst on a Scamp 13í deluxe

For some reason I can’t get a ohmmeter reading from the trailer 7pin ground to the frame of the trailer. Looked at the wiring from 12v batt and wiring (blk & wht) go directly to the out put 12v on the connverter. According to the installation manual on the pd9130 connverter it shows a frame lug on the back of the connverter to the frame. Looked for it and the lug is empty. Scamp wiring diagram shows brake ground to the rest of 12v grounds. But in checking the brakes they are grounded to the frame. If that is the case I should should see a ohmmeter reading from the frame to the brake thru the magnets to the blue(brake) on the 7pin. To summarize, I feel the chassis should be connected somewhere to the 12v circuit. Talked to a guy from scamp and he said the do-not bond the connverter to the frame because of circulating ground currents. I am aware of those but it does not seem to be worrisome in this application. Got a FCC radio tel license but does not help me out.
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Old 03-07-2021, 04:48 PM   #2
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Try from the frame to the white wire on the connector.
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Old 03-08-2021, 11:16 AM   #3
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Originally Posted by Joseph in Ark View Post
For some reason I can’t get a ohmmeter reading from the trailer 7pin ground to the frame of the trailer. Looked at the wiring from 12v batt and wiring (blk & wht) go directly to the out put 12v on the connverter. According to the installation manual on the pd9130 connverter it shows a frame lug on the back of the connverter to the frame. Looked for it and the lug is empty. Scamp wiring diagram shows brake ground to the rest of 12v grounds. But in checking the brakes they are grounded to the frame. If that is the case I should should see a ohmmeter reading from the frame to the brake thru the magnets to the blue(brake) on the 7pin. To summarize, I feel the chassis should be connected somewhere to the 12v circuit. Talked to a guy from scamp and he said the do-not bond the connverter to the frame because of circulating ground currents. I am aware of those but it does not seem to be worrisome in this application. Got a FCC radio tel license but does not help me out.
Tried that first. Also took a reading from the battery pin on the 7pin to the negative side of the battery and got 12.62v on that but same setup on the frames shows a 1volt drop to 11.67 volts.
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Old 03-08-2021, 11:24 AM   #4
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Originally Posted by Joseph in Ark View Post
I feel the chassis should be connected somewhere to the 12v circuit.
(I'm sure you know this already, but...)
The 12 Volt AC-to-DC converter is just for powering your lights and appliances when plugged in to campsite power.

All those devices have a +12 Volt wire and a Ground wire connected between them and the converter, so there's no need to connect the converter to the chassis/frame at all.

Now, how to help you diagnose your connection problem?
HERE'S a wiring diagram that shows the brakes connected between Blue and White, but not connected to the chassis.

Maybe someone rewired your brakes to the frame and someone else removed the harness-to-frame connection?

Anyway, I would like my brakes to not rely on the frame. Maybe just rewire them to the common ground wire.
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Old 03-08-2021, 11:33 AM   #5
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The White wire in the camper harness must be attached to the chassis.
They get rusty and detach. Find where it should be attached, clean frame to bare metal, reattach with a lock washer that will dig in and me, I coat it with Liquid Tape.
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Old 03-08-2021, 11:38 AM   #6
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Originally Posted by Joseph in Ark View Post
Tried that first. Also took a reading from the battery pin on the 7pin to the negative side of the battery and got 12.62v on that but same setup on the frames shows a 1volt drop to 11.67 volts.
Based on previous posts, it is my understanding that Scamp uses the frame as the return path for the brakes. With a 1 volt drop between +12 and the frame I'm guessing your ball is providing the connection. My solution would be to run a wire from the frame connection to the negative battery terminal. Also, watch any frame connection for corrosion issues, especially if they used self tapping screws.
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Old 03-08-2021, 11:45 AM   #7
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Originally Posted by Darwin Maring View Post
The White wire in the camper harness must be attached to the chassis.
They get rusty and detach. Find where it should be attached, clean frame to bare metal, reattach with a lock washer that will dig in and me, I coat it with Liquid Tape.
It seems that FG trailer manufacturers like to attach wires to the frame with cheap self drilling screws . The screws corrode or they become loose leading to a poor connection .I remove the self drilling screws , tap the holes for 10/32 machine screws , clean the frame , reattached the wire / lug using SS screws and lock washers then coat the area with liquid tape
On my Scamp , Casita and Escape they used the frame as the return conductor
( DC -) for the trailer brakes so a good connection is necessary
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Old 03-08-2021, 12:56 PM   #8
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Quote:
Originally Posted by Joseph in Ark View Post
For some reason I canít get a ohmmeter reading from the trailer 7pin ground to the frame of the trailer. Looked at the wiring from 12v batt and wiring (blk & wht) go directly to the out put 12v on the connverter. According to the installation manual on the pd9130 connverter it shows a frame lug on the back of the connverter to the frame. Looked for it and the lug is empty. Scamp wiring diagram shows brake ground to the rest of 12v grounds. But in checking the brakes they are grounded to the frame. If that is the case I should should see a ohmmeter reading from the frame to the brake thru the magnets to the blue(brake) on the 7pin. To summarize, I feel the chassis should be connected somewhere to the 12v circuit. Talked to a guy from scamp and he said the do-not bond the connverter to the frame because of circulating ground currents. I am aware of those but it does not seem to be worrisome in this application. Got a FCC radio tel license but does not help me out.

Check the converter connections.
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Old 03-08-2021, 01:01 PM   #9
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Originally Posted by steve dunham View Post
It seems that FG trailer manufacturers like to attach wires to the frame with cheap self drilling screws . The screws corrode or they become loose leading to a poor connection .I remove the self drilling screws , tap the holes for 10/32 machine screws , clean the frame , reattached the wire / lug using SS screws and lock washers then coat the area with liquid tape
On my Scamp , Casita and Escape they used the frame as the return conductor
( DC ) for the trailer brakes so a good connection is necessary
WRONG... The green wire on power cor connects to safety ground. the when the converter os connected to power the negative side is connected to the frame of the trailer. The white wire and the green wire are connected to ground (earth) at the shore power breaker box. This prevents shocks if should touch the frame and earth at the same time and there ie current leakage someplace in the system.
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Old 03-08-2021, 03:43 PM   #10
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Originally Posted by Byron Kinnaman View Post
WRONG... The green wire on power cor connects to safety ground. the when the converter os connected to power the negative side is connected to the frame of the trailer. The white wire and the green wire are connected to ground (earth) at the shore power breaker box. This prevents shocks if should touch the frame and earth at the same time and there ie current leakage someplace in the system.
I donít understand what your objection is ?
The brakes on my trailer has one wire connected to the 12VDC supply from the brake controller and the other wire is connected to the frame
The 120 VAC equipment ground ( Green) in the power cord is connected to the equipment ground bus in the converter panel and is bonded to the metal chassis of the trailer .
My point was that plated self drilling screws make a poor connection because they have a tendency to rust / loosen
If the frame of my trailer is not bonded to the negative from the battery then how are my brakes able to function ?
Not going to argue with you
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Old 03-08-2021, 04:24 PM   #11
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Im thinking Byron Kinnaman might have been under your camper one day when you were not there. After all, he is an electrical engineer.
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Old 03-09-2021, 08:41 PM   #12
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Name: Joseph
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Chassis/frame bonded to ground on12v.

[QUOTE=Joseph in Ark;807611]For some reason I canít get a ohmmeter reading from the trailer 7pin ground to the frame of the trailer. Looked at the wiring from 12v batt and wiring (blk & wht) go directly to the out put 12v on the connverter. According to the installation manual on the pd9130 connverter it shows a frame lug on the back of the connverter to the frame. Looked for it and the lug is empty. Scamp wiring diagram shows brake ground to the rest of 12v grounds. But in checking the brakes they are grounded to the frame. If that is the case I should should see a ohmmeter reading from the frame to the brake thru the magnets to the blue(brake) on the 7pin. To summarize, I feel the chassis should be connected somewhere to the 12v circuit. Talked to a guy from scamp and he said the do-not bond the connverter to the frame because of circulating ground currents. I am aware of those but it does not seem to be worrisome in this application. Got a FCC radio tel license but does not help me (Quote)
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Old 03-09-2021, 08:42 PM   #13
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Name: Joseph
Trailer: Scamp
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[QUOTE=Joseph in Ark;807833]
Quote:
Originally Posted by Joseph in Ark View Post
For some reason I canít get a ohmmeter reading from the trailer 7pin ground to the frame of the trailer. Looked at the wiring from 12v batt and wiring (blk & wht) go directly to the out put 12v on the connverter. According to the installation manual on the pd9130 connverter it shows a frame lug on the back of the connverter to the frame. Looked for it and the lug is empty. Scamp wiring diagram shows brake ground to the rest of 12v grounds. But in checking the brakes they are grounded to the frame. If that is the case I should should see a ohmmeter reading from the frame to the brake thru the magnets to the blue(brake) on the 7pin. To summarize, I feel the chassis should be connected somewhere to the 12v circuit. Talked to a guy from scamp and he said the do-not bond the connverter to the frame because of circulating ground currents. I am aware of those but it does not seem to be worrisome in this application. Got a FCC radio tel license but does not help me (Quote)
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Old 03-09-2021, 09:13 PM   #14
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Name: Joseph
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Found the problem. The ground bar on the ac/dc distribution panel,back has 3wires inside trailer where the converter is located. One is a 10 gauge to the 7 pin,one I 12the white and goes to the ground bar mentioned above and a large(bigger than 10 gauge) and bare goes from ground bar to the same location as the as the other 2. It goes thru the glas wheel well. When out side and found a double lug block. From what I can see is a 10 gauge wire in one of them and what appears to be a 12 gauge solid. To tired to follow up. May be tomorrow. Buy the way the screw holding the double lug ground blocks to the frame was rusted off and block was and just laying against the rust on the frame.
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Old 03-09-2021, 09:17 PM   #15
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Originally Posted by Joseph in Ark View Post
the screw holding the double lug ground blocks to the frame was rusted off and block was and just laying against the rust on the frame.
If you want to have trailer brakes all the time in the future, you can decide to rewire them and not connect them to the frame, but rather, wire them to the trailer connector directly with a reliable wire.
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Old 03-09-2021, 09:31 PM   #16
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Thanks for all the ideas every one of you
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Old 03-10-2021, 08:26 AM   #17
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Originally Posted by AlanKilian View Post
If you want to have trailer brakes all the time in the future, you can decide to rewire them and not connect them to the frame, but rather, wire them to the trailer connector directly with a reliable wire.
Exactly what I did.. I will not reply on a electrical connection to the frame for my brakes. I did leave the frame connection in place, but also ran parallel ground wire from the brakes to a junction box where the 7 pin wires are connected (another upgrade from Scamps wire nuts). Unless a rat chews the wire it is a very dependable method. And even then the frame connection might still be in place if it has not corroded away.

Quote:
Originally Posted by Darwin Maring View Post
Im thinking Byron Kinnaman might have been under your camper one day when you were not there. After all, he is an electrical engineer.
I'm pretty sure he was thinking of the 120 VAC wiring. Why I dont know since this thread is all about the 12 VDC side.
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Old 03-11-2021, 10:01 AM   #18
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EE or E

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Im thinking Byron Kinnaman might have been under your camper one day when you were not there. After all, he is an electrical engineer.
Electrician and Electrical Engineer both start with an E.
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Old 03-11-2021, 10:32 AM   #19
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The Answer: I questioned a manufacture of RV converters and here is the answer.

Hi Darwin,
You ground your A/C circuits to the ground bus bar, which grounds to the frame.
You ground your D/C circuits to the frame or battery negative.
Do not ground your D/C circuits to the A/C ground bus bar, as there is only enough locations for your A/C circuits.
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Old 03-11-2021, 01:41 PM   #20
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Quote:
Originally Posted by DuaneQ View Post
Electrician and Electrical Engineer both start with an E.

One has a degree and the other one knows what he is doing.
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