Air Conditioning - Trane Airhandler fan running

I have a trane AC/heat split unit. The AC portion works fine with no problems but when I switch to heat the fan starts running and will continue to run while in heat mode the heating element will cycle on and off while on but fan just stays on all the time. It also has a 2 speed fan and seems like its on the higher speed when it should be in the lower speed for heat. Any suggestions to check?

From the contents of your message I take it that you do not have a heat pump, that the outdoor unit is for cooling only and your heat comes from having electric strips in the discharge of the unit indoors. Is this correct?

Can you send MFR & M/N information for t-stat, outdoor and indoor units?

Yes its has heat strips and is not a heat pump. I had it on yesterday and as I said. It works perfectly except for the fan remaining on while the heating element cycles on and off.

Studying the schematic of a system is always quite helpful, which is why I had asked for the MFR & M/N for both of your units (outdoor & indoor), as well as same info for the T-stat.
I "may" be able to get the electrical info if I know the M/N's.

Was it always like this?

With Gas & Oil heat, there's a delay in fan operation (both, at the beginning & at the end). With heat pumps there's no delay-ON. With electric there's no delay either at the start of a cycle.

With heat pumps and electric heat, fans typically run with 1 speed (winter or summer) b/c of the much lower supply air temperatures compared to gas/oil which are much higher (so the CFM's lower and consequently the blower speed too)