From a letter by LuangPor Panyavaddho to a disciple, undated but probably sometime during 1979.
... In connection with the Citta, I can only explain it as I have understood it from Tan Achaan.
Firstly, one must not try to understand the Citta from the view point of the khandhas. The Citta is the fundamental and "real" one which does not die and which cannot be understood from the viewpoint of Sa.msaara because it is beyond Sa.msaara. Therefore one cannot say that it is or it isn't, nor where it is nor when. All such categories are of Sa.msaara. Nor can one say that it goes from life to life because this is a Sa.msaara viewpoint which sees the real importance as being "life": but the Citta is the real one, not this life or that life, and it has no goings or comings. Unfortunately however the Citta is permeated with Avijjaa. Finally speaking the Avijjaa is no more real than anything else in Sa.msaara, but it does effectively prevent the Citta knowing its own nature because of which it is modified and goes out searching for that which is real, true, beautiful etc. In other words it searches for is own fundamental nature in external things and due to Avijjaa in its mode of Tanhaa it grasps at a body to be an "image" of itself and it animates the body by functions of the Citta, these being Vedanaa, Sa~n~naa, Sankhaara and Vi~n~naana. But always these are unsatisfactory (Dukkha) because they are a substitute for the Citta itself, and they are Anicca, Dukkha, Anattaa, whereas the Citta is Nicca, Sukha, Attaa (Attaa as being the contrary of Anattaa - but not a "self").
With regard to the modifications of the Citta, the Citta is 'real' and Sa.mSaara is 'unreal' because it all Anicca, Dukkha & Anattaa, so from the viewpoint of the Citta these things are all phantom like and the real nature of the Citta never alters. So although the Citta is deluded by Sa.msaara it is really deluding itself because it imbues Sa.msaara with its own delusion (i.e.: we see people, animals, horses, trees without realising that they are all mere Sankhaaras and quite impersonal phenomena). The greatest delusion of the Citta is the rooted view that Self or Soul is within, or part of the five Khandhas. The Khandhas are quite unnecessary to the Citta, but because the Citta does not know its own nature it grasps them tightly being unable to comprehend what it would mean without them. If the Citta does not have the five Khandhas it fears that it will vanish and disappear into annihilation. But in fact they are a great burden and load on the Citta and due to Avijjaa are poison because it is by means of the five khandhas that we constantly make Kamma. To the Arahant, however, they can still be of use for teaching others and helping the world in various ways. Without a Citta the five khandhas cannot operate: they die.
I don't know TCH's views about three Cittas, but fundamentally there is only one. But when one talks of the modifications of the Citta they do sometimes talk of this Citta and that Citta. Then in the Abidhamma they describe 89 (I think) Cittas, such as 12 rooted in Lobha, 4 in Dosa and 4 in Moha (the figures may not be correct, I can't remember it now). But all these are modifications of the Citta and calling them different Cittas is just a way of speaking.
From the viewpoint of Sa.msaara, the Citta is mysterious. One text I know of talks of it having the characteristics of will, knowing and action. The action being non Kamma forming in the pure Citta.
The things that can pop up out of the Citta are incredible. They are all Sankhaaras so they form together like clouds then break up and disperse. The reason for their arising are rooted mainly in the past, but it probably needs a Buddha to understand their full extent.
The trees can of course throw out new shoots, until they are cut down at the roots by Pa~n~na. But it is a part of the daily practice to try and be mindful and use wisdom to avoid planting new seeds and pull up tender shoots before they grow strong.
PS. In fairness I must say that TA has not said all the above, but it is I think fairly based on his general teaching.