How do I manually engage the compressor when the pressure is to low?

Find the low pressure switch by the ac box and jumper it but i would do it for a long time since you might damage the compressor or other parts of the a/c system

Thanks

Do you want to bypass the low pressure cut off switch to refill the system or just to test it?

I was just testing it... low side seemed high enough for the compressor to engage, but for some reason it wasn't. All seems fine now though...