Problem with central heater

After thinking about all this and re-reading all the posts, I think you have a pressure or volume issue.  The regulator is good (the new one) and the pressure seems to be good (your post after measuring and adjusting the older regulator) so that leaves actual volume.  Could you have a pinched line under the furnace area??  A pinched/blocked line will allow pressure to build up and appear normal but when the furnace tries to draw alot of gas the flow is restricted.  Maybe a flare connection was made wrong.  Just a thought.

Thanks for the thoughts.  I put a new tank (a full 5 gal tank from my grill, that is full) on this morning, same problem.  Then, after talking to a technician at the RV repair shop, he said to replace the hoses between the tanks and the regulator.  He has seen this problem caused by them (they were both new with the rig, and probable from the same batch).  I did that, and fired it up.  That was an hour ago.  I'm going out to check it after a while.  If it isn't fixed, I will take the whole rig in to him tomorrow.
If a hose was crimped, it should be consistent.  What has been happening seems to go away after I let the water heater go through it's cycles a few times. (It fires up fine, burns with plenty of pressure for 15 seconds, begins fading away for 15 seconds, and goes out.  After 12 seconds, it fires off again and goes through the same thing.  Then, after doing this a few times, it keeps running).  Then, and only then, I can turn the furnace on and it will fire off and run (I do have to cycle it on and off a couple of times to get it to burn).  It runs fine until it gets up to temperature, then it turnes off.  When it gets cool, the fan turns on again, and the burner attempts to light, but it doesn't fire off.  At that time, if I turn the water heater back on, it acts the same as before).
If it is still working, when I go out to check it, I'll know the new hoses fixed it.  If not, it's beyond me, and I'll take it in.
Cliff

Monty,
I will definitly post the resolution to the problem.  I expect several of the folks that have responded will be interested.
The sequence you describe for your water heater is the normal operation when the gas hasn't gotten to the heater (it should try 3 times (12-15 seconds between each try) then stop and the red light turns on to let you know it's not lit).  Once the gas does get there, it should light and burn normally.  You can hear it when it lights the gas.  On mine, the light doesn't come on because it is getting gas, and burning long enough for the sensors to think it's working right.  Then, when the pressure goes down, it senses that and goes out.  Then, it's normal cycle is to try to relight, after 12-15 seconds.  So the cycle basically starts over.  Then, after several of these cycles, it stays lit and runs fine.  At that point the heater will also work.
Stay tuned for the next episode.  It's definitely going in to the shop tomorrow (I plan to be at the gate when they openat 8:30).
Cliff

Looking for answers from Cliff.

Thanks, seems like much hassle to figure out this problem.