andyrawlins When I turned guiding off the drift got worse.
Hmmm, this is odd, Andy.
By the way, I assume that by "guiding" on the Sun, that you mean "tracking," right? Auto-guiding can only be used with some specialized guiders that tracks the Sun. I use a Hinode Solar Guider (which uses ST4) for that
https://www.sciencecenter.net/hutech/Hinode-sg/index.htm
Anyhow, assuming that you mean "tracking", then try turning it off first and look at the rate and direction of drift.
When a telescope is stationary, the Sun should move 15º per hour (360º per 24 hours :-). This corresponds to 15 arc-minutes per minute of time.
So, as a sanity check, check if the Sun is drifting at this rate. You can estimate it by either finding the plate scale of your optical train, or, just roughly guessing by assuming that the Sun's diameter is about half of a degree in the sky. I.e., the Sun should drift by one of its own diameter in 2 minutes of time.
Note down the direction it is drifting (should be east to west in Right ascension only -- there should be just a small amount of declination drift that is caused by the earth's tilt).
Now turn on tracking.
The drift rate should go down to zero if you are set to Solar Rate. Sidereal Rate is 360º per 23 hours 56 minutes instead of 15º per 24 hours.
However, if the rate, instead of slowing down to zero, had doubled in drift speed (and in the same direction as the original drift), then I would suspect that the polar axis of the mount is pointed towards the south instead of to the north. In fact, this is how you can "drift align" the mount in the day time by using the Sun and look at the rate it drifts in RA and in declination.
Now, if the drift had doubled in speed, but in the opposite direction compared to tracking turned off, then something is horribly wrong with the solar rate of the mount. I doubt this is so with modern mounts that use quartz crystals for timing -- crystals are usually stable to better than 0.01%. So, if it had doubled in speed in the opposite direction, it would be a real head scratcher.
Good luck.
Chen
