7-Pin Connector Gets Too Hot

[madjack]

I couldn't agree more with Dale...20 plus yrs as a trucker, dealing with 7pin connectors tells me, Dale is gonna be on the money...I have seen perfect looking connectors have a bad connection and you have to go over each one individually to determine which it is.................................
madjack

[wlooper89]

So now you have switched the problem from the tail light circuit to the battery charge circuit......... Dale

Dale, you have a good point. I need to find the problem before switching to the battery charge circuit for tail light power.

My first step will be to measure the tail light amp draw. If it seems reasonable for 16 lamps on a #14 wire, the problem almost has to be in the tow vehicle connector/cable to the trailer. I have a battery charge/discharge meter in the trailer already, and if I connect the trailer batterry directly to the tail lights the amount of discharge will be the amp draw.

I did find one potential problem on the tow vehicle. My aftermarket hitch installer pulled the tow package wires (for a four flat connector) through a hole in the tow vehicle body in the tail light area where there was a rubber plug. But instead of making a hole in the center of the plug he left the wires along the side of the plug where they were pressed against a rather sharp edge of the tow vehicle body. I noticed deep indentations in the wire insulation and have how now corrected that. But this is upstream from the 7-way connector so I am looking at other possibilities.

Bill

[Dale M.]

A update of sorts and some pertinent information.........

Some measurements taken this morning........

Parameters are fully charged 12 volt battery (actual voltage reading was 13.15 VDC)

Multimeter is a FLUKE 78 III

The assumption is you are running 4 tail lamp filaments and 12 clearance lamp filaments.

Typical dual filament bulb for stop/ tail.... #1157

Stop filament draws 2.1 amp or 2106 ma.
Tail filament draws 0.58 amp or 0.575 ma.

Clearance lamp bulbs...

# 57 draws 0.22 amp or 0.221 ma.
#161LF (TL7) draws 0.17 amp or 0.176ma...

The above numbers are actual measured values... The totals below are calculated so give a little +/- for variation in individual bulbs ...

So your four tail lamps draws approximately 2.3 amps (.575 X 4 = 2.3)

Your approximate clearance lamp (total #57) draw is 2.652 amps (.221x12=2.562)...

Your approximate clearance lamp (total #161 LF) draw is 2.112 amps (.176x12= 2.112)

So your maximum draw (calculated) with 4 tail filaments and 12 clearance filaments is only 4.952AMP (using higher current #57 bulbs) ... Or with the lower current draw bulbs ( #161 LF bulbs) is 4.176 amp...

All numbers are well below maximum current rating of 7 pin connector and your wire gauge..... Most charts say your 14 gauge wire is sufficient, actually you could use 18 gauge but its a little light (maybe ok with LEDS)

This all sort of reaffirms (at least to me) a "mechanical" problem with connector...

Dale

[wlooper89]

Dale, thank you very much. That must have taken some time. It gives me an indication of what is normal. The brake/ turn signal pins in my 7-way connector were not hot so the problem seems to be just in the tail lights, those on the brown wire on a 4-way connector or green wire on a 7-way. My trailer has the extra 80" wide lamps, that is front and rear clearance lamps on each fender and a 3-lamp wide ID bar in the tail area, for a total of 7 extra lamps. My tail lights have dual fixtures on each side so that might also add two more.

Bill

[Dale M.]

Dale, thank you very much. That must have taken some time. It gives me an indication of what is normal. The brake/ turn signal pins in my 7-way connector were not hot so the problem seems to be just in the running lights. My trailer has the extra 80" wide lamps, that is front and rear clearance lamps on each fender and a 3-lamp wide ID bar in the tail area, for a total of 7 extra lamps. My tail lights have dual fixtures on each side so that might also add two more.

Bill

Sounds pretty close to lighting to my car carrier..... If I get pretty ambitious I may go down and put ammeter on whole rig to see if calculated values are close to actual....

UPDATE.... I actually did carry battery down to trailer (battery was actually on it's way to being put in to Baja Buggy that has starter problems) and put ammeter into circuit... Total amp draw was 4.87 amps.... That is for 4 clearance markers on each side ( 80 inch markers has 2 bulbs) for a total of 8 clearance, plus 3 bulbs for rear "wide load" marker on rear and the 4 filaments in tail lamp assembly... Total 15 filaments (no license plate lamp, its incorporated into one tail lamp assembly)

Dale

[Larwyn]

A voltage reading across that hot connector would tell a lot.

[wlooper89]

A voltage reading across that hot connector would tell a lot.

Larwyn , you are right. I will do that first and it is an easy test. Leaving the 7-way connector on the hitch opened up as it is now I can connect a long aligator clip connector wire to the tail light terminal in the J-box and the other end to the voltmeter negative probe. Then touch the positive voltmeter probe to the running light screw terminal on the tow vehicle connector. With the tow vehicle connected and runnings lights on, the voltage should be zero. Otherwise there is a fault. Those are inexpensive parts and easily replaced.

Good suggestion!

Bill

[wlooper89]

It is a rainy day in GA so I did the test that let me stay indoors first. Hooking up the trailer battery to all the trailer lights except brake/turn filaments the discharge reading was 5 amps with all 16 lamps burning brightly. This test was done at the junction box for the tail lights, behind the trailer tongue and did not include the overheating connectors. The amp draw of the lamps is about normal according to Dale's measurements. So there probably is not a short in the trailer running light wiring. I am glad not to have to go looking for that.

The next step will be to check for a voltage drop across the 7-way connector as recommended by Larwyn.

This is a little like an Easter egg hunt. Great fun!

Bill

[wlooper89]

After doing the tests you all have recommended I think the problem is narrowed down to the 7-way connectors. The tail light pins on both the plug and receptacle are discolored, from heat apparently. So I have decided to replace the connectors on both the tow vehicle and trailer. These will be relatively inexpensive. Both the new connectors are made by a company named Pollak so they should plug together well and make good contact.
It was a relief to find the amp draw of the tail lights is normal. Thanks again for all your help.

Bill

[wlooper89]

Hello again,

The new connectors arrived today. I think they will eliminate the bad contacts that were overheating. This is a photo of the connectors and, perhaps more interesting, an example of Patricia's quilting.



I have not actually done anything yet on the trailer but have been cogitating on the new wiring arrangement and came up with this diagram. Sorry, I have no training in the proper symbols for electrical drawings. One of the changes is to attach everything 12V DC negative to the trailer frame with a #10 wire, including the trailer battery. Not sure how that will work out but I want to give it a try. My main reason is that 12V negative is already connected to the trailer frame by way of the running light negative #14 wire and the battery charge circuit. That being the case it might be just as well to make a good connection with a heavier wire. AC is also grounded to the trailer frame and to the campground outlet through the power cord.

This is my amateur drawing of how I plan to wire the running lights. It is not very legible here, but the original is clear enough to use as my guide connecting the wires. When the wiring is all done I plan to keep my fingers crossed for good luck when first hooking up the tow vehicle and turning on the trailer lights.

Bill

[Dale M.]

Its ok to do it, just because you can, but why.... It only makes thing complicate .... And current loads are not enough to damage connectors on 7 pin...... Oh well enough said about that...

When doing wiring fix, go to auto parts or hardware store and get some silicone dielectric grease also know as "light bulb grease" (hardware store term) and when making new connections in connectors cut a little bit of old wire connection off to get fresh wire, and coat lightly newly skinned wire with the grease, this will keep oxygen out of connection and prevent corrosion from the brass terminals and steel screws in contact with the copper wire.... I also squeeze a bit into the slots of the 7 pin and exercise it a bit (plug/unplug) to coat terminals with grease, again to prevent corrosion...

People will say to NOT USE ANY GREASE on electrical connections.... BUT if connection has proper mechanical tension of components (tight) then grease is a non issue because you have good metallic contact with no oxygen in area to cause corrosion.... 38 years in telecommunications and literally thousands of connections made using non-oxidation grease products proves me right.... Beside its a telecommunications industry standard for making high current electrical connections......

Dale

[wlooper89]

I regret taking so long to make the changes to my tail light wiring. I had expected to have it done by now, but am having a flare-up of back pain from spine surgery earlier this year. Getting under the trailer on my creeper is a little bit daunting right now. But I will get it done and report the results as soon as possible.

Sorry, I made a mistake earlier describing my tail lamp wire size. In several posts I said it was #14 and that is true about the molded cable on the trailer tongue. But the tow vehicle came prewired for a flat-four plug and now that I have the aftermarket 7-pin connector open, it appears that the original tail light (brown) wire is at most #16 wire. Unfortunately the size is not stamped on the wire itself, but it is definitely smaller than #14. The trailer was originally wired for 4-pin plug and used #18 gage wire throughout. The 16 tail lamps are all connected to a single #18 brown wire with a single #18 ground wire for all lamps.

I am planning to add a relay so the only load on the tail lamp wire from the tow vehicle will be the new relay coil using original tail lamp power. The tail lamps themselves will be powered by a new #12 wire to a junction box. Since the tow vehicle tail lamp wire is smaller than I thought and the trailer has the extra 80" wide lamps, I will feel better doing it this way to lighten the load on the tow vehicle tail light wire. At the same time I can upgrade the trailer wiring by dividing the tail lamps into separate groups from the junction box to the lamps on the original #18 wires.

Thank you again for all your help.

Bill

PS Dale, I appreciate the heads-up about dielectric grease and will use that on the 7-pin connector.

[wlooper89]

There is a little progress on my new relay and wiring for the trailer tail lights. The relay/junction box will go in a tail light compartment on the Little Guy. The relay was designed to plug into a socket on certain late model cars to complete the tow package wiring. Not having a socket, I soldered wires to the four pins and used heat shrink. Velcro holds the components in place.

The first photo shows the larger junction box with relay and terminal strip inside. The next shows the small relay box open. I just need to tie up a few loose ends.

There is some more to do to attach matching Powerpole connectors in the tail light compartment and run a #12 power wire and a #18 relay coil wire from front to rear under the trailer. The tail lamps will be wired in groups of no more than four using the original #18 wires after the junction box. Colored electrical tape in various color combinations are to help plug in the J-box correctly.

Bill