Compressor ya umeme (variable displacement compressor) ina working principles tofauti kabisa na compressor with external cluth (fixed displacement compressor )
Compressor ya umeme inakua adjusted na computer ya gari (ECM) kuweza ku alter performance (output) ya compressor lakini pia condenser fan na bila kuumiza engine, ambapo compressor ya umeme inakua inatumia pressure ya upande wa HIGH SIDE inayokua controlled na solenoid ambayo ipo mounted nyuma ya compressor kuweza kubana pressure ili ile pressure isukume piston (tilting of swash plate that hold compressor’s piston together), zile piston zikisha tilt basi basi zinatengenesha pressure na suction na kufanye compressor iweze kusukuma gas upande wa high na upande mwingine (low side) uwe kuvuta gas (suction),,sasa baridi ikisha fika kama ulivo set, ile valve ya compressor ufunguka (hu release pressure) na kulinganisha pressure ndani ya compressor crank-case hivo piston za compressor hii ya umeme hurudi to rest position, hence no pressure is created..sasa ni kupitia hii switch control box ya gari ikishirikiana na climate control system huweza ku adjust pressure/performance ya compressor hii very precise na ndo maana compressor hii hata kama gari ipo silencer (idle) perfomance yake inakua pale pale kwakua performance ya compressor hii ya umeme haitegemei rpm ya engine kama compressor yenye clutch nje, na even performance wise compressor ya umeme ina ubaridi mkubwa kuliko compressor with fixed displacement compressor.
(note : pia kutokana na maelezo ya awali hapo juu, ndo maana compressor ya umeme haitaji kua na external clutch, na nyingi hasa hizi gari ndogo hazid kabasa na clutch.)
But ukitoa hii compressor ukaweka modified fixed displacement compressor basi computer inakua haina control na performance outpot ya compressor, na computer inakua haipati correct feedback ili kuweza ku adjust engine performance accordingly, hence injini inatetemeka na kufanye gari iwe nzito (kiasi cha kufanye gari hata kupanda mlima iwe shida), au kufanye injini kuzima kabisa pindi clutch inapo engage, vibration zinakua nyingi na fuel efficiency inapotea kabisa
Ni kwanini hali hii, ni hivi fixed displacement compressor (kipumbu) yenyewe it always operates at its full capacity regardless of cabin temperature level, yaan hata kipindi kiwe cha barid compressor hii yenyewe ipo at its maximum capacity sasa kwakua gari za kileo zinakua na climate control sysem yenye sensors zinazo determine temperature na humidity ndan ya gari, basi zile sensor zikisoma labda zinapeleka feedback kuambia climate control computer kupunguza ac performance by 40%, basi taarifa hii itapelekwa kwenye control box, na control box ita command kile ki switch cha compressor ku adjust swash plate ambapo ndipo piston za compressor ya umeme zipo attached to certain angle, hapo compressor output itapungua na utaona fen ya condenser pia speed itapungua,na engine speed itashuka pia, na kama watumia pressure gauges kusoma pressure upande wa high utaona pressure inapungua accordingly. therefore compressor ya umeme ipo na very good pressure control ya refregent compared to fixed displacement.
Sasa unapobadirisha compressor (yaan unatoa compressor ya umeme (variable displacement compressor) unaweka compressor ya external clutch (fixed displacement compressor) au kipumbu kama zinavoitwa Tanzania hapo huwa kuna shida kwakua working principles za hizi compressor mbili ni tofauti kabisa.. compression ya clutch ya nje it always operate at fixed displacement, na performance yake inaongeza ukikanya mafuta zaidi..hii compressor ina operate at its full capacity all the time regardless of temperature demand na haina adjustment yoyote ya output kama compressor ya umeme, therefore inakua ipo too heavy kwa injini (na ndo maana gari za kileo haziji na hizi compressor clutch nje AKA kipumbu.
Sasa uki fanya modification ukaweka compressor ya manual, wanachofanya mafundi huwa wana iungia ile solenoid switch inayotoka kwenye compressor ya umeme, then wanaongeza relay switch inayokuza umeme ili kuifanya compressor ya kipumbu ipate voltages 12 ambazo ndizo zinahitajika kufanye magnetic coil iweze kutengeneza magnetic fields pindi inapokua energized kuweza kuvuta ile clutch bila kuslip (kuteleza) (kumbuka compressor ya umeme inahitahi volts 3 mpaka 6 ku operate, so unapo weka compressor ya kuhitaji 12v unaongeza electric load to alternator.
Sasa ile switch huwa inaungwa kwenye hii modification ili kuidanganya gari izanie ipo na compressor yake ya umeme, sasa kwakua gari inakua bado inapata signals toka kwa ile switch basi gari ufanya adjustment ya mafuta na engine power kulingana na feedback ambazo kwa wakati huo zinakua si feedback zenye uhalisia kwenye gari, hivo gari uonekana kupungua nguvu lakini ni kwasababu gari ina act kutokana na feedback inayopata (mfano computer inapokea taarifa kwamba now because of heat load, the ac compressor should operate at 50%of its capacity, lakini kumbe gari imefungiwa compressor ya kipumbu ambayo always ina operate at 100% so pale compror inapobana clutch huku injini imesha jiandaa kupokea mzigo wa compressor inayotakiwa iwe operational at 50% inakutana na compressor ambayo ipo at 100% capacity hapo ndo injini ina anza tikisika, tetemeka, kupunguza nguvu hata kuzima kabisa.
Sasa nin hufa kwenye compressor ya umeme?
1. Mara nyingi (80% kufa kwa compressor ya umeme huwa ni ile switch ya nyuma ndo hufa) nayo hukaa muda mrefu ndo inakufa (kumbuka haya magari twayachukua used) sasa kama nilivosema hapo awali kwenye working principles za variable displacnent compressors, kwamba ile solenoid valve switch mle ndan inakua na kipin ambacho ni spring loaded, kinapokua energized na 3 volts kinachofanya hufunguka na kuruhusu pressure ya ac system isukume piston then kinafunga kuzuia pressure isitoke, then piston ndo zinaanza kuzalisha pressure ya kusuma gas (hii pia ndo maana compressor ya umeme huwezi test kama ni nzima ikiwa nje ya ac system) . Sasa kile kipin kwakua kina act against pressure ya ac system, withtime ile pin huanza choka na kushindwa kuhimili/kuzuia pressure inayosukuma piston isitoke na hivo kufanya compressor kufanye kazi na kuacha, but this valve can be replaced, badala ya kununua compressor nzima, unaweza agiza parts Ebay/Alibaba, ila kama unamtu anauza hapa bongo unanunua una replace compressor inaendelea kipiga kazi.
2. Bearing ya mbele ya compressor inaweza kufa (but this can also happen to any other compressor si ya umeme tu) kama mtoa mada anayo sema anasikia kelele, yawezena ni bearing ndo imezingua.
3. Compressor ya umeme pamoja ya kua always inazunguka injini inapokua on, likini ipo na mechanisms yake pale kwenye pulley ya mbele inapopita fen belts kiasi kwamba ikitokea compressor ime seize, basi tabs za pulley zitakatika ile injini iendelee kufanye kazi bila ya kuathiriwa na compressor iliyo kua seized. Na compressor u-seize because of increased friction inayosababishwa na poor lubrication.
4. Compressor ya umeme haitaki kabisa contamination (kukiwa na contamination kwenye system basi ile compressor hufa haraka sana na hii ni kwasababu ya design ya operation yake, ambapo ule uchafu ukijaa kwenye vitundu vya solenoid basi soloed huziba na kusababisha catastrophic failure ya compressor, but kwa compressor ya kipimbu nayo uharibika endapo system itakua contaimated ila tu itachelewa kidogo kwakua hii compressor ya kipumbu haina vitundu vidogo vinavozuia gesi yenye uchafu isipite.
Nini mafundi wa kitanzania ogopa hata kushawishi mteja aweke compressor ya kipumbu badala ya umeme.
Kama gari imeua compressor ya umeme kwa uchafu wa system, basi mafundi hushauri mteja anunue compressor ya kipumbu na condenser, then utaona anakuambia ana flush system. Then atafunga vifaa vyako utaondoka, but my friend this is just a trap (mtego) ni hivi gari ikiua compressor with black death, hapa hata uflash vipi system uchafu huwa hauishi (huwa unabaki kwenye evaporator, sasa fund itaweka ile compressor ya kipumbu kwakua haina vitundu vidigo vinavoweza kuziba haraka, na umeweka condenser yenye njia kubwa kidogo (kwakua condenser inayokuja kwenye gari yenye mfumo wa umeme inakuaga na njia nyembamba ingawa ni nyingi sana-ingawa ni nzuri sana, zina large surgace area for heat dispersion), atakushauri kuweka hivo vitu ili kusogeza muda wa system kusumbua tena maana kama ni compressor ya umeme na system hajasafishika vizuri, basi compressor ya umeme hufa siku hiyohiyo au palepale au itafanya kazi siku moja na itakufa, but kwa compressor ya kipumbu inaweza fikisha hata mwezi mmoja ila uta note kitu unapokua low speed au silencer utaona ubaridi unapungua. Sasa ili ku deal na hili tatizo na kulibu completely unatakiwa kuabadili the entire system components (yaan compressor , condenser, expansion valve,evaporator pamoja na pipes zote) lakini pia kuweka genuine r134a gas, na compressor oil original designed for compressors uses r134a refrigerant ambapo huwa ni oil namba ND-08 or PAG oil no 46., pia gari itatakiwa kupigwa vaccum ya kutosha kuondoa all the moisture contents Ndani ya ac stystem… and speaking of moisture (unyevu unyevu) kwakua twanunua condenser used, inapendeza kama ukinunua desiccant bag (utambi wa condenser) ambao kazi yake ni ku absorb all moisture contents Ndani ya ac system, pia ni kama filter.
Pia kwakua mafundi wengi wa ac bango hawajui kutuma gauge kupima ac system lakini pia hata wakitumia gauge wao huwa wapo interested kupima upande wa low side wa ac stytem kuona ac compressor inavuta mpaka PSI ngapi, yes yawezekana wapo sahahi but kuna vitu havipo sawa ambapo ukifanya kazi kwa mazoea kwenye compressor ya umeme possibilities za kukosea na kubwa sana..kumbuka compressor ya umeme ina control yenyewe pressure bila kutegemea engine RPM, sasa mtu anaweza kukomaa na pressure wakat contor ya gas inaona the prevailing pressure ni adequate kulingana na hali ya hewa, hivo ukakuta gauge haikupi majibu fundi anayotarajia hvo anaweza kuweka gas nying akaidhan system inashida na kusababisha overcharge ya ac system na kusababisha hydrolocking ya compressor na ku seize kabisa (kumbuka compressor intaka gas ya ac iingie in gaseous format na sio liquid form, so too much refrigerant leads to excessive pressure and too much liquid, hence chances to hydro lock the compressor become so high. Solution ni ku charge gas by weight. Kila gari inakuja na sticker inayo onyesha weight inayo ingia kwenye system ya ac ya gari husika, na mara zote sytem ya ac za umeme zinachukua gas kidogo ukilinganisha na sytem same car size but with manual (kipumbu) compressor.
Hivo kwa upande wangu mie gari napenda inayokuja na compressor ya umeme, na kama DIYer (do it myself), always do car maintenance by myself,na gari ikizingua compressor ya umeme, natafuta nyingine naweka na maisha yanaendelea.hii ni kwakua compressor ya umeme ipo na perfmance ya hali ya juu kuliko kipumbu, na kwakua it always run at low pressure hivo na low load kwenye injini, hivo low fuel consumption, and with clutchless operations there Is no engine jerking, the car runs very smooth with no power loss even during heavy ac operation-mfano wakati wa mchana. ((kumbuka compressor ya umeme it goes beyond on and off of clutch kama inavofanya kazi ya compressor ya kipumbu, compressor ya umeme take control automatically to adjust performance accordingly, compressor head pressure, ile kuifanya gari i operate at its most efficient manner given various variables)
Na ninapenda fanya mwenyewe hizi issues kwakua mafundi wetu sisi hapa Tanzania si mafundi bali ni parts changers, yaan wengi hawafahamu principles ya namna vitu vinafanya kazi matokeo yake solution zao zinakua si kukusaidia wewe, bali solution wanakupa inayo match na uwezo wao wa knowlage na kukucharge pesa isoyo endana na unachokihitaji au kistahili.
