Printing in the air

If this question has been answered before sorry I couldn't find it.
I built a Mendel90 1.5v with Gen 7 motherboard and ATmega1284P chip. I'm using Marlin 1.0.0 because it's the only one I can get to compile right for now. I'm also using Arduino IDE 1.8.12 and Pronterface to do the printing.

Here's the problem my z axis stop switch is at the top left as per the build manual. The z axis always homes to the top stop switch. When I go to print in Pronterface the z axis doesn't lower to the bed it stays at the top and tries to print in the air.

Because I'm using Marlin 1.0.0 I do not have a line that says #define Z_HOME_POS 0, I only have #define MANUAL_Z_HOME_POS 0.

The distance from my stop switch to the bed is 188.50mm.

I do not have auto bed leveling, figure I might add that later.

Can some one please tell me how I get the z axis to come down to the bed when printing.

Thank you. Kenn

Z_MAX_POS should be where your limit switch is, i.e. 188.5mm and the homing directions should be 1 and the switch defined to be a max limit.

This is what my config looks like for a recent version of Marlin

#define X_HOME_DIR 1
#define Y_HOME_DIR 1
#define Z_HOME_DIR 1

// @section machine

// The size of the print bed
#define X_BED_SIZE 200
#define Y_BED_SIZE 200

// Travel limits (mm) after homing, corresponding to endstop positions.
#define X_MIN_POS (-X_BED_SIZE / 2)
#define Y_MIN_POS (-Y_BED_SIZE / 2)
#define Z_MIN_POS 0
#define X_MAX_POS (X_BED_SIZE / 2)
#define Y_MAX_POS (Y_BED_SIZE / 2)
#define Z_MAX_POS (178.6)

This is on an early prototype machine with a shorter Z axis due to being fitted with an E3D V5 hot end that is very long. I defined the X and Y limit switches as max as well to give a conventional bed orientation viewed from the front.

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