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Solve decoupled PDE's with NDSolve?

I have one NDSolve with a system of equations that solves just fine 

NDSolve[eqns1, depVars1, {z,0,zf}, {t,0,tf}]

I have another completely decoupled NDSolve that solves

NDSolve[eqns2, depVars2, {z,0,zf}, {t,0,tf}]

But when I put them together...

NDSolve[Join@@{eqns1,eqns2},Join@@{depVar1,depVar2},{z,0,zf},{t,0,tf}]

even when they're completely decoupled, I get the error "The given initial conditions were not consistent with the differential-algebraic equations." Anyone know why?
POSTED BY: Eric Smith
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Check the attached file. It works (gives the interpolating functions), but they look similar!

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POSTED BY: Christos Papahristodoulou

I replied to the wrong thread. Anyway, I've updated your notebook with the problem I'm seeing. I appreciate the help; I can't figure this one out.

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POSTED BY: Eric Smith

Hi! Just a grammatic error in equations...eons =; Correct it to eqns and you get the solutions (Interpolating functions)!
POSTED BY: Christos Papahristodoulou

Thanks, but this is a copy-paste of some code. I added “eons” (should have been “eqns”) for this post. Did you happen to try the code? It fails for me

Update: original typo fixed
POSTED BY: Eric Smith

That's right, the first set of equations solves fine. My question is when adding another equation (given in post) it fails. I'm adding to the notebook and will send it back in a few minutes
POSTED BY: Eric Smith

Works for me on my example. I guess it has to do with your code. Generally speaking, except for very common errors, problems with code require the code for the problem to be diagnosed.
POSTED BY: Michael Rogers
POSTED BY: Eric Smith
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