Under 20F my wait to start light rotates on and off about once per second. Eventually it will stop and go through the normal warming cycle. Plugging in the block heater helps, but it's about 7F and I've been waiting over an hour for it stop, even after being plugged in all night. I replaced the grid heater about a month ago, but that had no effect. I've uploaded a video...
http://www.youtube.com/user/jdk7204#p/a/u/0/K7jBl-9TnsY

 

It may be the relay for the grid heater. Looks like an old starter relay used on chryslers and fords in the '60. Mounted next to the pass battery.

 

Thanks, is there any way to test the relay?

 

looking it up in the service manual.

 

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I don't know what year 3rd gen you have, but the relay coil on the '07 is powered by the E.C.M. If the relay coil is drawing to much power the E.C.M. will shut down the circuit and try to power it again. this could be caused by a bad ground connection to the relay coil or the power connection is loose / corroded or the relay is bad. The ground is at the body ground bolt. Could be many other causes, but this is a place to start. The coil wires for the relay are the small wires.

 

just thought too. there are some gaskets running around out there that are NOT metalic. the grid heater is grounded thru that gasket/bolts (the reason for metalic gaskets) from the horn thru into the intake plate. if you are not getting proper grounding thru there, that can cause issues too.

 

Why is the amp or volt gauge not working when turn the truck on.

 

Thanks for all the inputs. The gauges don't move when it does this. However, when it's warmer and it starts normally, everything comes alive like it's supposed to. It warmed up enough today to get it started and when I did I used the key trick to get a P2509 code. It's for ECM/PCM Power Input Signal Intermittent. So it sounds like Thunder Road is on the right track. I'll see if I can see anything loose or corroded. Thanks for the help.

 

Carefully check all the battery cable connections. I think what is happening is that when the intake heater comes on it draws a lot of current through a bad connection and starves the ECM of power. This causes the ECM to shut off the intake grid heater. Then the cycle starts over.