After replacing truck lights with LED's, TT lights act weird

[Bear25314]

I have a 2011 F250. I replaced all the marker light bulbs with LED's. Now, when I attach my TT, the marker lights on the TT act differently. The brake lights work fine, however, when I turn on a blinker (either one), all the marker lights begin to blink as well. Also, when I press the brake with the blinker on all the marker lights on the TT come on steady. I am at a loss. Thanks in advance for any pointers.

[wa8yxm]

Question: This only happens when you have the trailer attached?

If the answer is YES.. Check the GROUND connections, both at the Tow Vehicle (first) and at the trailer.

Even with standard (NOT LED) lights I had issues when towing my car behind my motor home with the turn signals not working.. Did a SERIOUS improvement of the Ground (motor home end) and ... Instant joy.

LEDs are far more suspictable to grounding issues it turns out.

[happycamper002]

KD4UPL wrote:
The flasher circuit now has a much smaller load on it then before. Years ago you needed to swap out the flasher in the truck for one that was compatible with LED lights. I'd look into that. I don't know if you can change them out on the new trucks.
One way to get around that was to wire a regular bulb in parallel with the LED lights so there was more current draw. This will make the flasher circuit work properly again. The problem is this kind of defeats the point of putting in LED's if you're trying to reduce current consumption. You still get the longevity and cool look of LEDs.

You can buy the resistors as dummy loads that increase current low load demand that LEDS are designed for. Flashers are still manufactured the way they were 100 years ago. These flashers cause the contact to make and break through a bimetal pathway--causing the blinking depending on the electricity that is going through it. Look on ebay. They sell hundreds of them. LEDs are great but they are not "plug and play". In some applications,they could act weird and even affect other electronics. Consumers should have been made aware of this but they didn't. A lot of them are not DOT approved.

[DownTheAvenue]

Unlike incandescents. LED's have a specific positive and negative. What has happened is that some LED's have been installed backwards and the positive is back feeding through a negative wire causing the problem.

The center post of an incandescent socket is positive and the metal side on the socket is the negative. Reposition all of your LED's so that the positive post is in the center of the socket and the negative is at the sides.

If the bulb is the type that just pushes in like an number 7443, then one side of the push socket is positive and the other is negative. Just turn the bulb around and reinstall. If is is a bayonet type base like a 1157 bulb, then identify the positive of the LED and make that contact with the bottom of the socket.

NOTE: this has nothing to do with the truck. In fact if the LED's are all installed on the trailer only, all the truck recognizes is the electric load not the type of bulb. Now replacing LED's on the truck itself, that can cause issues.

[Bear25314]

Thanks. I'll try switching some of the lights back to incandescent and see if the trailer lights go back to normal. Oh, and yes, I did it strictly for a "cool look". It's all good.

[SoundGuy]

KD4UPL wrote:
One way to get around that was to wire a regular bulb in parallel with the LED lights so there was more current draw. This will make the flasher circuit work properly again. The problem is this kind of defeats the point of putting in LED's if you're trying to reduce current consumption. You still get the longevity and cool look of LEDs.

This is about a "cool look"?!! Good grief. :S

[corvettekent]

Its most likely a bad ground wire on the trailer.

[SoundGuy]

Bear25314 wrote:
I only replaced the bulbs on my F250. I travel trailer has the original incandescent bulbs. Could it be a ground wire?

No, it's your truck which wasn't designed to work with LED bulbs. Reinstall the original incandescents and your problem will go away.

[KD4UPL]

The flasher circuit now has a much smaller load on it then before. Years ago you needed to swap out the flasher in the truck for one that was compatible with LED lights. I'd look into that. I don't know if you can change them out on the new trucks.
One way to get around that was to wire a regular bulb in parallel with the LED lights so there was more current draw. This will make the flasher circuit work properly again. The problem is this kind of defeats the point of putting in LED's if you're trying to reduce current consumption. You still get the longevity and cool look of LEDs.

[Bear25314]

I only replaced the bulbs on my F250. I travel trailer has the original incandescent bulbs. Could it be a ground wire?

[SoundGuy]

Bear25314 wrote:
Thanks in advance for any pointers.

Not all vehicle electrical systems are compatible with LED bulbs in the trailer's exterior lights. My suggestion - reinstall the original incandescent bulbs, 'cause that's what your F250 is designed to power.

[RoyB]

I never wanted to change any of my DOT safety lights out for the LED types as this never was a power consumption issue from my battery banks. All the power to operate the safety lights comes from the truck battery not the trailer batteries.

The LEDS are very sensitive and low DC voltages probably back feed into things very easy...

I know my trailer ceiling LED lights sometimes are showing a very dim light even when they are turned off sometimes...

You may have a hard time tracking these events down haha... Most likely all ground related perhaps...

Roy Ken