93 wiring harness woes - no power

Been pulling a yard trailer for years using the factory 7 pin wiring harness. At some point a trailer wire became abraded resulting in a short that popped the 20a fuse in power distribution panel (#23 trailer tow). Replaced the fuse but see no voltage at the end of the trailer wiring harness (testing by plugging into a new set of wires/lights and looking for 12v via meter on the trailer side harness connector.

Next I looked for voltage in the interior fuse panel at #5 (15amp), #4 (15amp) and #10 (15amp). All fuses were good and showed 11.6 - 11.75 volts. All other electrical components are functioning properly.

So I supect all that leaves is the trailer wiring harness relay(s) located in the driver side rear tool box next to the rear window washer fluid reservior.

However, I see TWO relays. The Ford dealer tells me there is only ONE and the part numbers on my relays don't match the number the dealer tells me.

My questions are -

1) How do I test these relays to make sure they're working? Probe a connection point and touch ground with the other side of the meter?

2) I think the relays are OK as I can hear them 'click' when I apply the brake pedal. If the relays are OK, what is interrupting power to the harness?

What am I missing in the process here?

 

[MountaineerGreen]

Been pulling a yard trailer for years using the factory 7 pin wiring harness. At some point a trailer wire became abraded resulting in a short that popped the 20a fuse in power distribution panel (#23 trailer tow). Replaced the fuse but see no voltage at the end of the trailer wiring harness (testing by plugging into a new set of wires/lights and looking for 12v via meter on the trailer side harness connector.

Next I looked for voltage in the interior fuse panel at #5 (15amp), #4 (15amp) and #10 (15amp). All fuses were good and showed 11.6 - 11.75 volts. All other electrical components are functioning properly.

So I supect all that leaves is the trailer wiring harness relay(s) located in the driver side rear tool box next to the rear window washer fluid reservior.

However, I see TWO relays. The Ford dealer tells me there is only ONE and the part numbers on my relays don't match the number the dealer tells me.

My questions are -

1) How do I test these relays to make sure they're working? Probe a connection point and touch ground with the other side of the meter?

2) I think the relays are OK as I can hear them 'click' when I apply the brake pedal. If the relays are OK, what is interrupting power to the harness?

What am I missing in the process here?

I have never known a pre 2005 Explorer to have a 7 pin harness- are you sure it is factory? Could it have been added prior to your buying it? And if so are there any fused wires under the hood?

The way to test relays is find the two coil terminals, one should be power, one should be ground. The other two or three terminals are the terminals it switches- If the input terminal is A, then A and B would be connected when the power is off, when power is applied to the coil, A and C would be connected, disconnecting A and B. Check etrailer.com, they have some pretty good videos about trailer wiring.

 

[kjhume]

wiring harness woes - no power

Thanks MG....yes, I am the original owner and this is the factory harness for sure. Its a round connector, 7 pin male that connects under the drivers side rear bumper.

I'll do the research on testing the relays...at $50 a pop to replace them I want to be certain they are the problem.

 

[Blackskull]

I have never known a pre 2005 Explorer to have a 7 pin harness- are you sure it is factory? Could it have been added prior to your buying it? And if so are there any fused wires under the hood?

The way to test relays is find the two coil terminals, one should be power, one should be ground. The other two or three terminals are the terminals it switches- If the input terminal is A, then A and B would be connected when the power is off, when power is applied to the coil, A and C would be connected, disconnecting A and B. Check etrailer.com, they have some pretty good videos about trailer wiring.

I have a 93 XLT and it also has a 7 pin factory trailer connector.. and that I have located which pins are for the lights and brakes and attempted to install a tapped 4 pin connector behind the 7 pin wiring plug,, I have approx. 11.5 volts on the appropiate pins but when I plug my boat connector in to the Explorer, I get zip for lights on the boat. I unplug the boat, check the supply and it is there.. I am using a digital meter , but I checked the boat on my old ranger and the lights all work.. What am I missing about the wiring on the Explorer?
Blackskull...