T cell 40 tests ok but not making chlorine??

[waterbear]

Need a bit more info. Do you have any lights on the unit turning on or do you just not have any FC in the water? Please post a full set of test results for starters (include FC, CC, pH, TA, CH, CYA, and Salt). Have you increased your pump run time for when the pump is on low speed? Chlorine production is a function of output percentage (with a Goldline unit it means that your cell is on and generating for 65 minutes out of every 100 minute cycle for you 65% output percentage, then the cell reverses polarity and starts again) AND the pump run time so, for example, if you were running at 65% for 6 hours at 3450 rpm then you would need to run the pump for about 10-12 hours at 1800 rpm to maintain the same water turnover (but would have much lower electric costs which is the advantage of a multispeed pump AND you might have to turn the cell output down a bit for even more savings) SO, once again...
Have you increased the pump run time for the lower pump speed? Flow rate does play a part.