B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 178; Flight Crew Total 18000; Flight Crew Type 706
Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft; Manuals
Caution light on Takeoff. Pressurization Auto Fail.Green ALTN illuminated.Pressurizing normally in Alternate mode.Continued climb while running QRH procedure. We got to spot in procedure that did not make sense to us. Alternate was working normally but the procedure directed to manually operate the outflow valve because Auto Fail light was still illuminated.  We re-ran the checklist twice to double check and make sure we were not making a mistake.Not seeing need to manually operate the outflow valve; we contacted Dispatch and [Maintenance] for additional guidance.  Maintenance control also concurred with my reluctance to manually operate outflow valve while alternate was working. [Maintenance] was able to produce an older version of the checklist and stated that it read differently than our current version but could not recommend following that because even though we don't know why; it was revised for a reason. He would not say that it is ok to continue climbing and continuing on a four hour flight with functioning alternate mode. Dispatch then got [Chief Pilot] on the line and reviewed the checklist with me as well and came to the same conclusion. We agreed that the best course of action would be to 'pause' the checklist where we were and return to [departure airport]. We left the pressurization controller in alternate mode and returned for an uneventful overweight landing. Used emergency authority to 'pause' the checklist and to make overweight landing.Some unresolved issues are:Why would a procedure direct you to go to manual mode with a functioning alternate mode?I used ACARS to get hold of Dispatch. I got two messages from Dispatch stating they were trying to make the connection through [communications] but 'we're having issues'. After what seemed like nearly 10 min; I called [Company Radio] and had them call my Dispatcher directly. During this time; we were getting further and further away from [departure airport]. We previously had decided to continue towards destination with the hopes of resolving the fault and being able to continue. Ultimately; this was not the case and we ended up over 200 miles away from [departure airport] before turning around.Although it was not critical for this flight; other than burning more fuel; it was a very time-consuming process to establish contact. If it had been a more serious in-flight emergency; the delay in making contact may have been more critical and should be addressed.
[Report narrative contained no additional information.]
B737 flight crew reported returning to departure airport following the loss of the pressurization auto mode on the takeoff roll.