I have a DSZC16 manual indicates 2 stage compressor does that mean it increases speed when needed?

Yes, that is correct.

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Your throttle body is dirty and needs to be cleaned....Buy a can of throttle body cleaner.
Now you have 2 options....you can either do a remove and replace cleaning- or you can do a semi clean.,,,simi meaning leave the TB on- but spray the cleaner in- and move the plate back and forth to dislodge the accumulated crud. either way- is your choice....
But when you clean it- disconnect the battery for at least 30 min... so that it loses any bad learned settings...good luck, i hope this helps.

Hi, this thermostat is for central heat and air systems that have more then 1 stage of heating or cooling. For example, your unit may have 2 stages of cooling, as in 2 compressors, or 1 stage of cooling and 2 stages of heating as used in commercial heat pumps. This is a multi-stage heat pump thermostat. It may be just a matter of programming the stat. If you can find a manual on it, this would help. If you open the cover, it should have directions on how to program it.Make sure you have power to everything, check all breakers to see if they may be shut of, even if you have a display, doesn't mean you have high voltage to run the unit. Make sure fan is in auto, and on heat or cool, and temperature set for it to come on. Please keep me posted.
Sincerely,
Shastalaker7
A/C, Heating Contractor
PS Your unit has 1 stage of cooling, and 2 stages of heating.

Dear Hamza,
High Temperature at First Stage means your Second stage is becoming Weak and it is not capable to pull the maximum air from First stage, If it is only at loaded position.
If this is your regular problem you must check your Water condition it should not be below 20 degree C and not above 40 degree C.
You may also try to blow some dry air into second stage ( HP Element ) when ever it is in off position.
Hope this will help you.
Regards
Ashfaq

depends on what relief valve it is, if it is a 2 stage pump and it is the relief on the inner-stage that is lifting indicates the second stage is not pumping correctly! I would check for a broken valve. if it is the one on the discharge line to the tank, then something is restricting it, check for blockages in the line or in the check valve entering into the tank. Most important you isolate the compressor and drain all air pressure before you attempt any repairs

Here is info I found "Pump:
Two Stage, Cast Iron, Compressor Pump, 5 HP, 17.1 CFM Maximum Free Air Flow At 175 PSI Maximum, 2 Cylinder, Oil Capacity 2 Quarts, Pump Speed 685 RPM, Bore Size 4 3/4 x 2 1/2 Inches, Stroke 3 Inches, Motor Sheave Diameter 6.75 Inches, Flywheel Diameter 16 1/2 Inches, W 18, Depth 16 1/2 Inches, Height 22 1/4 Inches, Outlet 3/4 Inch NPT, Mounting Holes 8 3/4 x 5 3/4 Inches"

What bearing did you replace? Check belt tension. there should be less than 1 inch of deflection.

hi when the compressor is not running the levels should/must be the same when it is running the stages push the levels up in the last stages hope this helps merlin v12

I would be glad to help with your project, sounds like you are a tinker-er. Most all compressors whether one or two stage are plumbed the same. The important difference is that two stage compressors are made for a higher pressure range. This means that the tank must be able to safely hold more pressure than single stage. Other considerations are that the pressure switch, safety valve, check valve, regulator and all the tubing would need to be upgraded. Finally two stage compressor takes longer to cycle because of lower volume. If you want to continue, post again listing the parts that you already have.