You have a Suburban water heater so real good chances same Brand was used for furnace.. (Did you finally get it to light off and heat water???)
When you set t-stat to heat and set temp higher then trailer temp furnace fan should come on and blow cold air for 30-90 seconds (purge cycle to remove any possible gas fumes prior to ignition)
Then when conditions (sail switch makes up from adequate air flow) have been met 12V DC power is applied to gas valve and spark electrode at same time. Power for gas valve is on for 6-8 seconds and then if no main flame power is removed to close gas valve.
Do you hear the 'click, click, click' of spark electrode?
Does main flame even light off for few seconds?
If you are getting spark but no main flame then
*gas valve solenoid could be bad
*Main orifice on gas valve could be plugged
*burner could be dirty/clogged with rust/debris
*spark electrode may not be correctly positioned (centered directly over slots)
*spark electrode gap may not be correct (1/8")
Suburban Furnace Manual....numerous models
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31