Cummins grid heater spiking voltage?

jmtandem wrote:

My trailer is lightly used and I have already had to replace the LED brake and running lights. Today, I replaced all my amber LED marker lights which were obviously smoked. I have an 04 Ram and am wondering if the truck is sending an over-voltage to my running lights.

When I cold start the truck the grid heater will cycle causing the headlights to dim and the fan motor to slow. In a minute they will speed up and brighten. This is from the outset even with new batteries. Would this voltage fluctuation have an impact on my trailer lights?

Any ideas to protect my trailer running lights? Should I wait for the engine to warm before turning on the lights? Do they make voltage regulators I could dedicate to my running lights circuit?

All of my truck lighting has no issues but is incandescent.

All you are experiencing with the truck is perfectly normal. And, no, it is not taking out your trailer lights. You have another issue somewhere.

Totally agree.
You are not seeing "spikes", your seeing the voltage sag and then come back to normal. It is not affecting your running lights at all other than their supply voltage is dropped down to around 12 volts for a couple of seconds.
Nothing to worry about.