Lighting voltage??

[JimM68]

As I was setting up to tow my wrangler a few weeks ago, something seemed weird.
As I'm triple checking the wiring in preparation for installing an smi stay n play, something is for sure wierd.

At the jeep. I'm reading 8.6 volts at the parking lights. Brake lights are the same.

At the motorhome, I'm reading at the umbilicle connector, and at the front and rear corner marker lights.

Rear lights on the motorhome are getting 9.6 volts.

Front lights on the motorhome getting 10.6 volts.

Symptoms include:
lights on the wrangler are very dim.
If the wrangler is attached, the motorhomes turn signals do not flash if the brakes are on. True regardless of weather the moho's running lights are on or not.

Here's a kicker for you: If I turn on the lights in the jeep, the tail lights on the moho get noticeable brighter. With the jeep's lights on, I now read 11.2 volts on the moho's right rear corner light, and 11.8! on the right front!

This all is telling me:
There is resistance in the moho's lighting circuits, and it is dropping voltage.
I think that resistance is ahead of the front marker lights, like maybe at the headlight switch?

any clues on how to find it?

I need to fix this asap. July 8 we leave on long trip, lights and smi brake have to work.

[subford]

What is the battery voltage reading?
What is the voltage reading at fuse 6, 8, 19 & 12 in the diagram below?

/

[JimM68]

Battery voltage is 12.6 engine off, 13.8 engine on.
Same in the RV custom products DC control center, where the relays and such are.

I ran a voltmeter down all the big fuses in the "ford fusebox" in the engine compartment, center under the hood, all read 12.6 (engine off)

I really need to look at the wiring in the back. I saw those toad relays in my diagrams, but from the quick glance I had, my toad wiring appears to be spliced into the motohomes tail lights. With big house wiring style twist on wire nuts. :(

[JimM68]

ok, did some checking by the "light of night" Also pulled one of the sockets down.

First, my ground is not the greatest. I'm dropping .7 volts from my ground wire to true ground (the frame) This is easily fixed and is not my problem.

Measuring at the tail light socket, I had 8.8v, 9.6 when I ran a jumper to ground ground so to speak.

I checked all the bulbs carefully. I have no totally open grounds.

Other than the low voltage, there are no apparant problems with the tail lights, or any of the other exterior lights for that matter. But there's not enough power when the toad lights are added to the occaision.

[JimM68]

There is no separate trailer harness on this rig.

The wiring run coming over the spare tire to the rear cap has 5 wires.
Black ground.
Brown running lights.
Yellow and green turn / brake
And a red one, which is brake light only.

The lights are 2 over 1 on each side. All three are tail lights. All three are brake lights. Only the bottom on each side is a turn signal.

The harness is easily seen and accessed in the cavity between the body and the cap. the trailer harness really is wire nutted into the cap harness! There is no separate relay controlled trailer wiring.

The light sockets I inspected have male spade connectors, and the harness wires plug in with female spades

I'm not averse to picking up the toad wiring up front and running another wire run to the back of the rig. I'd like a 12 volt wire to keep the toad battery charged anyway. Any idea where I can tap into the dedicated trailer wires?

[subford]

I can just tell you how Ford wired it.
email me at subford(AT)gmail.com and I will email you the 1999 Ford F53 Diagrams for the lighting.
The (AT) above = @

[speed racer]

Check the connection where the turn signal switch plugs into the wire harness it gets hot and burns the connections. Ford had a lot of problems with the turn signal switches. They even had a recall on them a while back and you might check on that.

[JimM68]

Thank you subford, email is on the way.

Speedracer, that sounds like the ticket for sure. Can you put a location on that problem connector?

[JimM68]

Here's my thought right now.

Whatever is wrong with the exterior lighting on the moho wasn't even noticed until the add'l load of the toad lights was added.

The actual problems right now are:
Taod lights are very dim.
Turn signals don't flash if the brakes are on.

Plus the percieved problem of the 2 electrical systems being connected.

So, I'm gonna fix it with relays. Toad wiring runs high thru the engine compartment and right past the battery. 3 bosch relays screwed to the airbox and a hot lead off the toads battery = problem solved.

I'm also going to pick up 12v fused at 20 amps, and bring it back with a new 12 gauge wire to keep the toads battery charged.

And I'm going to make darned sure the back of the moho, the umbilical, and the harness on the toad have a good solid ground.

Sound good?

[wa8yxm]

Difference between front and rear lights.. Nearly 50 feet of wire one way. Try switchign to LED rear lights

Difference between Motor Home and towed.. Another fifty feet (25 each way)

Do check the ground wire on the wiring harness. Odds of it being 1/4 the size it shoudl be or even smaller.. Right close to 100%

[speed racer]

A freind of mine has a a 98 model MH and ford replaced his T/S switch 2 years ago under a callback for fire hazzard. The connector is in the shroud around the steering shaft.

[RinkersRanch]

When you said an electrical circuit was acting 'weird' that tells me it is probably a ground problem. I use to tell my guys in my basic electrical class, "if it's acting WEIRD its a ground". When the ground side of a circuit is weak or broken the current is going to do its best to find a way back to ground. This can cause current to flow back wards in some components causing voltage loss and in some cases 'weird' things to light or work when they are not turned on. Weird things like 'the right turn signal blinks when i turn on the left one', 'the backup lights come on when i hit the brakes'.
Use a digital volt meter and look for voltage on the ground side.
Here is a hint on a way to do this. Turn on the 'weird' acting circuit. Connect the black probe on the neg side of the battery, and the red probe on the ground circuit as close to the component (light) as possible, there should be '0.0' volts reading on the meter. Find voltage (any reading above 0.1v.) on a ground leg, you found a problem. Clean connections or run new grounds. Make the ground voltage go away and the 'weird' problems go away.

[JimM68]

Thanks for all guys.

As I said, I've chased plenty of bad grounds in my time, and I don't believe this is.

I am going to check the turn signal switch in my rig.

I've solved this problem by building and installing a small panel with 3 "bosch" relays in my wrangler.
The tail light, and left and right turn wires from the moho go to the relay coils, the wiring to the taods lights feed off the normally open contacts. There is a 20 amp autoreset breaker, and a 12 gauge charge wire to the moho.
I put in a secure ground to the jeeps fender, 5/16" bolt with star washers, and ran a 12 gauge ground wire from there to the umbilical.

It all works great. jeep tail lights are plenty bright now.

[JimM68]

also, need to add, the jeep turn signals were backfeeding, lighting either lit both. I put a couple diodes in the jeeps wiring harness to cure this. I used ordinary garden variety diodes, maybe a buck each, and spliced them into the lt and rt turn signals feeds from the jeep, line toward the back of the car.