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Hello, my name is***** fault suggests a loss of vacuum to the temperature control head usually caused by cracked vacuum reservoir. Unplug the Black vacuum line under that hood that goes into the firewall, install a vacuum pump, check to see if it holds vacuum. If it does not hold vacuum, access the rear of the temperature control head, remove the black vacuum line, install vacuum pump in its place, see if the control head can work all temperature doors normally, if it can't, suspect leak in control head, or one of the blend door actuators. If the control head and actuators hold vacuum, then there is a leak between the source vacuum and the control head, or the check valve is bad. Access the vacuum reservoir tank behind the dash, test both the tank and the check valve, replace as necessary. Let me know if you have more questions or if there is anything else I can do to help. Thanks.
Is it normal at 3000rpm or on high acceleration to lose some vacuum? See now is working much better but only on normal acceleration if you can say that.
No it is not normal. Let me know if you have more questions, thanks.