remote start rpm fluctuate w heat

Hey Guys,
I just installed an Ultra Start 1272 with an Int-SL bypass on my 2003 Chevy Silverado 2500 HD last night. I got it starting, locking/unlocking. When I leave the heat off, and remote start the car, the car runs fine. When I leave the heat on, and remote start the car, the RPM's get really low and fluctuate a little running rough. If I start the car with the heat on and with the key, everything is fine.

I did not hook up the Brown wire on the ignition harness, one site said that wire was a 3rd ignition, another said it was a 2nd accessory, could that be the problem? I hooked up....

Truck Orange to Ultra Start Accessory Green
Truck Yellow to Ultra Start Yellow Starter wire
Truck Red to Ultra Start Red
Truck Pint to Ultra Start Blue Ignition 1
Truck White to Ultra Start White Ignition 2

Thank you very much!

Just did a 2002 Silverado with an Ultra Start last week.  It was a 1500 with the 5.3L V8.  No issues with idle during remote start. 

I did run in Tach Mode and connected to a F.I. wire :

There is a connector at the back of the fuse box that has all of the controlled ignition wires.
I added an external relay controlled by the Black AUX1 wire ( reporgrammed to (-) Accessory Output, Menu 1, Item 5, Opt 1 ) for the trucks Brown ACC2 wire.  Both ACC's are very heavy gauge.

I also split the U1272s'  two Red +12V constant wires between the trucks Red and RED / White +12V constant wires shown below.  On the 2003 they might both be Red.

Extra relay wiring :

Relay Pin 86 and Pin 87 to +12v constant thru 20A fuse.
Relay Pin 30 to vehicle Brown ACC2 wire.
Relay Pin 87A not used - insulate.
Relay Pin 85 to remote start Black AUX1 wire.

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Soldering is fun!

Thanks a lot for the reply. Maybe that is my problem...I connected the two red power wires from the ultra start together and then to one of the red power on the truck. Do you think I need to split the two?

Also...the blue antenna light blinks when the car is locked...I never saw that before but I'm thinking that may be an option?

Due to the gauge of the trucks ignition wires, I felt it prudent to split the U1272's load between the two available +12v source wires.  The additional relay for ACC2 was connected to the same source wire as the U1272's Red wire that supplies the starter output.

As for the Brown ACC2 wire, there is another post, https://www.the12volt.com/installbay/forum_posts.asp~TID~128550~PN~1, that suggests that it might have something to do with the O2 sensors.  That could affect idle quality.  I usually try to duplicate with the remote starter exactly what a key start does.

The U1272's Blue antenna lights blinking when locked is a nice feature.  It gives the impression of an alarm system and some extra peace of mind.  It is user programmable.  See Menu 3, Item 7, Opt 1 if you don't want the blinks while locked.

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Soldering is fun!

while it shouldnt affect as ive never seen this fluctuation and i do primarily gm accts i dont see whether you have tach hooked up, i would recommend hooking up the tach feature( it is a white wire on back of the instrument cluster) other than that i see no logical reason for the fluctuation as the brown acc wire is power for windows not a primary ignition wire, but verify that your wire hooked to the trucks white wire is staying powered thru crank and not dropping during crank

I should also mention that when I go to start it remotely...it doesn't always start. It sometimes goes like it is going to start and then cut out and try again a few seconds later.

I did hook up the tach of the remote starter to the tach wire on the bypass because it said the int-sl gets the signal from the data wire attached to the truck

Think I would connect the U1272 Tach wire to a vehicle Tach source, either the White wire Jim Hunter suggested behind the instrument panel, a F.I. as pictured or the ECM.  You must do a System Reset to the U1272, re-program any non-default options ( with the exception of the selectable relay ) and then start the vehicle with the key.  A successful Tach Learn will give 2 horn beeps and 2 parking light flashes.  Ideally, the engine should be warm and at a normal idle.

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Soldering is fun!

Ok. I will be sure to hook up the tach wire. Thank you.

Which one would you do? Fi or behind the cluster?

Thank you guys very much...I'd love to get this resolved!

Keeping the wire inside the vehicle and out of the engine compartment has its' advantages.  I believe on your model year, you can pop out the vent / parking light control assy at the left of the instrument panel and locate the White Tach wire in a group of wires with some gray tape on them.  Should be the only white wire there but verify with a Digital Multi Meter.  Jim H does  plenty of these trucks and can explain better...

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Soldering is fun!