My A/C system works fine but it only works when the fan is on High Speed. Is this normal or is something wrong in the system.

Sounds like you need a new fan motor resistor. It is located behind the glove box. Easy to replace, usually costs about $20

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2006 KJ Sport CRD, 2006 KJ LTD CRD, 2013 Subaru BRZ 6spd., 1994 Ford F150 XLT, 1969 Dodge Charger R/T 4spd. (Yes it's a Hemi).

Both posts leave some ? on the table. To the OP are you saying your AC 1) cools only when the fan behind the grill is running on high or 2) cools fine but the fan in the cabin HVAC unit only runs in the high (#4 IIRC) position.

Cannot help with #1 but if #2 then mrhemi is right. See my tech tips PDF at http://colorado4wheel.com/manuals/Jeep/KJ/ for how to and PN. Not as to PN you need to purchase based on noted PN or vehicle model to get the heavy duty one.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs