PART NO.  SPL.PAGE  DESCRIPTION                                                           
AHH5601   15.R.42   Air control cable and Knob Assembly -(heater, 1500)
AHH5601   16.R.45   Control cable and knob assembly -air -(heater, 1600 and 1600-MK-II)
AHH5602   15.R.42   Demist control cable and knob assembly -(heater, 1500)
AHH5602   16.R.45   Control cable and knob assembly -demist -(heater, 1600 and 1600-MK-II)
AHH5786   TC.R.56   Control -push-pull -air (long) -(heater, heat+vent eqiuip, Twin
    Cam)
AHH5786   TC.R.57   Control -push-pull (air) -(fresh air vent equip, Twin Cam)
AHH5787   TC.R.56   Control -push-pull -demist (short) -(heater, heat+vent eqiuip, Twin
    Cam)
17H827    15.R.43   Knob -(for AHH5601 control ass'y, heater, optional, 1500)
17H827    16.R.45   Knob -(for AHH5601 control ass'y, heater, optional, 1600 and
    1600-MK-II)
17H827    16.R.45   Knob -(for AHH5602 control ass'y, heater, optional, 1600 and
    1600-MK-II)
17H1683   TC.R.56   Knob -(air control, heater, heat+vent eqiuip, Twin Cam)
17H1683   TC.R.56   Knob -(demist control, heater, heat+vent eqiuip, Twin Cam)
17H1683   TC.R.57   Knob -push-pull (air) -(push-pull air, fresh air vent equip, Twin Cam)

AHH5601 Heater air control cable, item 18 in the illustration at right. For all MGA except Twin cam, and excluding early 1500 cars with twist switch.

The MG Series MGA Driver's Handbook, Second Edition shows this style heater control, and no longer shows the earlier style with twist switch in the cable control head. Actual date of change of this control assembly was not document anywhere, but I suspect it changed at the same time as the dash instruments face style at (C)14090 in April 1956, so only about 4000 early production cars would not use this part.


Complete cable assembly. Outer jacket assembly. Inner cable assembly.
Photos provided by Scott C in Cumming, Georgia, USA.

I was trying to define the correct length of the cable assembly, since the one Scott had to remove from his car was too short, and the new one was correct. The quotes below are from Scott C, while the follow-up notes are mine.

"The mounting collar is adjustable as both the chrome and bras nuts move in and out". -- Okay. I thought the front collar was fixed, with a bonded knob. So I check and took picture of mine, and indeed it does have removable knobs and front threaded bezel nut. I'm sure proper assembly is for the front end of the threaded housing to be flush with front face of the chrome nut. So the first picture on this page shows an incorrect cable assembly. Picture at right is like original and the current replacement part.

"Okay more accurate numbers. 40-3/4 from dash mount to sleeve end. 1-5/8" wire exposed with switch depressed. 1 travel to index in the pull shaft".

It is not particularly bad if the assembly is longer than needed. Replacement parts are often used for various applications, so the longest one needed may be supplied, and you can trim it shorter if needed for other applications.

17H827   Knob -Heat and Vent Control -(1500, 1600, 1600-MK-II)
17H1683 Knob -Heat and Vent Control -(Twin Cam)
I believe this is original style for the control knob for the Air and Demist controls for all MGA, Including early 1500 and all Twin Cam (correct me if I'm wrong). This is a snap-on knob, press detent pin underneath to release it from the shaft. As far as I know, the two part numbers are identical parts, just a different number assigned for introduction of the Twin Cam model.