Trailer connector no power

[bobbylinn52]

I have a 2007 Safari Cheetah.  Last week, Tuesday October 10, I removed the battery boost solenoid with the intent of installing a Blue Sea ML-ACR but ran out of time so I reinstalled the old continuous duty boost solenoid.  On Thursday, October 12, I hooked up the TOAD, for a trip, and no electrical power.  There is no power or ground to the 7 or 4 way plug.  I took photos of the wiring before I remove the battery. boost solenoid and rewired it exactly as in the. photos.  I have checked all of th fuses I know about or can find, with a meter, for trailer signals, brakes, lights.  All are good.  Today I  ran a ground wire from the chassis battery ground. to the rear of the coach to test continuity.  There is continuity to the frame but not to the ground in the trailer plug.  I connected the know ground. to the ground in the trailer plug but still no power for any of the lights.  I pushed a T pin into the ground wire by the plug and have continuity through the plug.  I and focussing on the ground assuming since everything is dead it is a ground issue.  I even put the jumper onto the house batteries, just to check, no continuity to the plug ground there either.  I did not expect the plug to be grounded to the house batteries.  I am lost at this point.  Is there a breaker I don't know about?  The Safari Cheetah only has the electrical bay in the left front under the drivers window.  I have search this site and found nothing similar to this.

I just LOVE electrical issues.

[Steve P]

I had good fuses and a bad relay at one point.  I think that only affected my brake lights, but I have slept a few times since then, so I'm not sure.  Swap same part-numbered relays (a known good one with the possible bad one).  Mine were in the left front run bay and the right rear run bay;  no idea where yours might be, sorry.  Look in the files section for a wiring diagram if you don't have one.  And good luck... I hate electrical gremlins, but at least yours is a persistent problem rather than being intermittent. 

[Tom Cherry]

1 hour ago, bobbylinn52 said:

I have a 2007 Safari Cheetah.  Last week, Tuesday October 10, I removed the battery boost solenoid with the intent of installing a Blue Sea ML-ACR but ran out of time so I reinstalled the old continuous duty boost solenoid.  On Thursday, October 12, I hooked up the TOAD, for a trip, and no electrical power.  There is no power or ground to the 7 or 4 way plug.  I took photos of the wiring before I remove the battery. boost solenoid and rewired it exactly as in the. photos.  I have checked all of th fuses I know about or can find, with a meter, for trailer signals, brakes, lights.  All are good.  Today I  ran a ground wire from the chassis battery ground. to the rear of the coach to test continuity.  There is continuity to the frame but not to the ground in the trailer plug.  I connected the know ground. to the ground in the trailer plug but still no power for any of the lights.  I pushed a T pin into the ground wire by the plug and have continuity through the plug.  I and focussing on the ground assuming since everything is dead it is a ground issue.  I even put the jumper onto the house batteries, just to check, no continuity to the plug ground there either.  I did not expect the plug to be grounded to the house batteries.  I am lost at this point.  Is there a breaker I don't know about?  The Safari Cheetah only has the electrical bay in the left front under the drivers window.  I have search this site and found nothing similar to this.

I just LOVE electrical issues.

Unfortunately, we have, in the files, no prints on the Safari.  I’m of the school….when you mess with something.  Odds are, with Monaco, you get unintended consequences.  IF I understand….but let me ask questions….

First….using your KNOWN GROUND….directly from the chassis (or the House….doesn’t matter), did you test everyone of the other 6 pins as well as the 3 pins.  What I mean….use your VOM.  Start with Parking lights.  The turn signals on some DVM is tricky.  If you put a piece of wood or have someone gently push on the brake pedal, you will get a signal on the remaining 3 pins of the 4 pin socket.  If NOW 12 VDC on any pin, using a known ground…..you are chasing the wrong thing.

Again, I don’t know your coach, but MOST of the rear light signals come from a relay.  There are 4 that come to mind.  Park, LT, RT, Charge…  those 4 relays get a signal from the front.  Pins 85 & 86 are energized.  You need to find these relays.  There is a 12 VDC signal coming back.  That goes to the coils.  Use a small piece of wire or long meter leads or even straight pins.  Look on the relay.  It shows which pins are 85 and 86.  Turn on the park lights….pins or the wires in the socket for 85 and 86 have to measure at least 10 VDC…obviously all the wire and the length of the run decreases the voltage.  OK…back to the park relay.  There are two pins used.  TYPICALLY pin 30 is used for the incoming power.  There is a FUSED, Direct Chassis battery line to either pin 30 or pin 87.  When the relay closes….the circuit between 30 and 87 is made.  Use your meter lead….Pin 30 should be HOT, when measured to the known chassis ground.  BUT…it could be pin 87.  ONE has to be.  If you have a 12 VDC signal (pins 85 & 86) and one of the pins (probably 30, but if not 87) is HOT….then the relay “board” or sockets should be good.  The three signals, Park, LT & RT all work that way.  If you charge your Toad battery, there is a separate relay….and a 20 amp fuse.  There is an Ignition ON for it….again to 85 or 86….then pin 30 has a 15 Amp fused lead…87 takes it to the 7 pin.

OK….not knowing….if you blew the power fuse for the Park, LT & RT relays….then pin 30 (or 87) will be dead.  Find it….fix it.  BUT???? Could be this….read on…

There is a harness coming INTO where the relays are…..and one going out.  If you disturbed that….either one….you lost the incoming power (control signals) from the front…..or the voltage to the 7 pin….the OUTGOING Relay signals.  I would find the two harnesses and the plugs.  Pull apart & reseat….

Unless you were crawling under the hitch, you probably did not mess up that connections.  We have folks that are working around harnesses and inadvertently bumps a major plug….then they “loose” it all.

SO….I might check the harnesses first….if you get that FIXED, then you use your VOM & a known ground….and test the 7 or 4 pins on the MH.

Good Luck….let us know….

 

[bobbylinn52]

Tom,  Thanks for the reply.  I tried all six terminals with a VOM using the ground jumper from the chassis batteries. I tried all six terminals with the ignition off, on and running.  I also checked the 4 pin plug the same way.  I have found fuses for the L & R turn signals, brakes, and tail lights.  All test good using a VOM.  I inserted a pin into the wires for the ground and brake lights then checked continuity between these pins and the contacts in the female trailer plug.  There is continuity on these two wires.  In the battery compartment is the device shown below.  Two wires are labeled; "trlr chg gnd and trlr chg". The other two wires I haven't found labels on them yet.  I have not unplugged this device. Is this a relay?

 

 

 

[Tom Cherry]

OK….the fuses, unless the safari is different May BE the fuses to the relays.  The device in the picture is a standard BOSCH 5 pin or terminal relay.  Without the circuit, there will be four wires on that relay.  When the ignition is turned ON, there is a Plus 12 VDC signal wire to the relay.  Pin 85 or 86.  Again, unplug the relay from the socket.  On the side of the relay is the pin diagram.  If the ignition signal or wire goes to pin 85, then there has to be a Ground to Pin 86.  These are the coil terminals of the relay.  There will be an upstream 15 A fuse going to pin 30…(maybe 87…but most likely terminal 30).  When the ignition turns on….the relay closes.  Power is sent to the charging terminal via pin or terminal 87.  The LT, Park, & RT works the same way.  So, if you tested the charging or 12 + VDC terminal on the 7 pin, the ignition needed to be on.

I’m back to my first hunch, there is a harness that has two connectors….one bringing in the front signals…that goes to the relay.  Then the fused wires go to pin 30mof eqch function….and the outgoing harness or wires go to the individual lights.  Now, there will be MORE wires in the bundle.  Start at the trailer connector.  See where there is a harness connected to another harness.  Pull apart….reseat.  Then chase that harness to,the next connection.  Eventually you will get to the one that I think was bumped accidentally.

[MyronTruex]

To lose all of the functions on the plug is not likely related with anything you were doing. 

Making an assumption here that you have tested both battery banks to see that they are charge? Start the rv and give it a couple of minutes. Then test both large terminals on the old solenoid you put back in place. The reason or goal is to be sure you have power to the relays involved with the plug.

The ground could be a separate issue but here is what I feel might be the problem.

They build these chassis with a basic wiring harness, and then they add to those to accomodate different length coaches and different layouts.

Put some safety goggles on and grab a headlight. Start right at the back of the trailer plug and follow the harness to wherever head bumping knuckle bleading place you can. Somewhere you are likely to find a heavy duty plug that needs some exercise. 

I know this seemed to happen when you were in the battery compartment but I cannot count how many time these seemingly strange events occurred in my shop. Had a customer leave and come back with a problem  we seemed to have caused. It turned out his old trailer wiring had shorted out and we got the pleasure of another hour of repairs on us. But that stuff happened so often I would ask my techs, "did you fix the other three things that are broke". 

[Tom Cherry]

Myron has a LOT of experience.....and information.  All I can reiterate....we have had more...  "WHAT DID I DO" posts from doing upgrades, probing around, just pulling harnesses, etc. than I can count.  I DID find a drawing on the MH....or it will be close....

Go to the Coordinates in the left..... G/H6.  That shows the wiring.  If you blow up the drawing and start to chase each pin, it is connected.."roughly".. in my opinion, through a maze of "Connections".  Working in the RRB and such, one often has to "move" things.  

SO...based on the fact that the entire plug DIED....and there are several different relays upstream...  I'm still of the opinion that there is a harness connection that was "disturbed.  
 

So, NOW, you can follow the Relays for each function....and if the Relay's are "sending out a signal....as I think ALL of them are...then there is a common denominator....as in a multipin harness connector that got bumped...  

BUT....I have been known to be wrong before....ask my DW....I think twice before she got up...  LOL...  Until you start with the Relays....determine if there IS a good signal....then it is all over.

BTW....you never commented...and I never asked.  DO THE MH TAIL LIGHTS WORK OK?

IF SO....then the Relays are OK.  I THINK that you said that you do NOT have a GROUND in the 4 or 7 pin....and when you used a KNOWN ground....that the power or signals didn't work.  THAT IS THE KEY....a bad connection....and doing all the trouble shooting of the relays, as they also control the Tail Lights...might be the SECOND STEP....as in checking the harnesses and the plugs....

BUT....That's just my thoughts....but NOW you do have the drawing...

2006 Diplomat & Other years Overall Chassis Wiring Front to Rear....BLOW IT UP.pdf

[bobbylinn52]

THANKS TO ALL!  THIS IS RESOLVED.

This blind sow found the acorn.  As Tom and Myron suggested I started at the trailer plug and began following the cabling.  I did not find a loose connecto, but a connector completely unplugged with the snap latch broken.  I reconnected the plug, tested and then zip tied the plug together as it was very easy to pull apart without the snap latch.

Edited October 17, 2023 by bobbylinn52