一輛2002年款上海通用別克賽歐轎車，用戶反映該車總是燒毀散熱器電子扇熔絲。經詢問用戶得知，該車之前出現過冷卻液溫度過高的故障，于是在外邊找了一路邊店進行維修。經過相關維修人員檢查發現，儀表板左下方熔絲盒上的散熱器電子扇熔絲熔斷。更換新的熔絲后試車，當電子扇高速運轉時，熔絲再次熔斷。維修人員檢查線路未見異常，故判定為散熱器后方的電子扇電機內部存在短路故障導致熔絲燒毀，于是又更換了散熱器電子扇，但試車故障依舊。
接車后，根(gen)據(ju)用戶(hu)反映(ying)的(de)(de)(de)情況，維修(xiu)人員(yuan)先換上(shang)新的(de)(de)(de)熔絲(si)進行試車。當散熱器電(dian)子扇低(di)速(su)運(yun)(yun)轉(zhuan)(zhuan)時，2個電(dian)子扇的(de)(de)(de)轉(zhuan)(zhuan)速(su)、轉(zhuan)(zhuan)向都正常；當電(dian)子扇轉(zhuan)(zhuan)為高(gao)速(su)運(yun)(yun)轉(zhuan)(zhuan)狀態后，冷凝器前方的(de)(de)(de)電(dian)子扇高(gao)速(su)運(yun)(yun)轉(zhuan)(zhuan)狀態良好，而(er)散熱器后方的(de)(de)(de)電(dian)子扇只(zhi)轉(zhuan)(zhuan)一下便停(ting)了下來(lai)。難道是剛換上(shang)的(de)(de)(de)熔絲(si)又斷(duan)了?經檢查發現，熔絲(si)果然又被燒斷(duan)。維修(xiu)人員(yuan)根(gen)據(ju)維修(xiu)經驗(yan)判斷(duan)，熔絲(si)被燒毀的(de)(de)(de)原因多是熔絲(si)后部(bu)至用電(dian)設(she)備前的(de)(de)(de)線路(lu)搭鐵或(huo)電(dian)子扇內部(bu)局部(bu)短路(lu)。

經查(cha)(cha)閱電(dian)(dian)(dian)路(lu)圖得知(zhi)，該(gai)熔絲(si)到(dao)繼(ji)電(dian)(dian)(dian)器K70的(de)(de)線(xian)(xian)路(lu)走(zou)向都在(zai)儀表臺(tai)內(nei)部，想要對(dui)整條線(xian)(xian)路(lu)進(jin)(jin)行排查(cha)(cha)費時(shi)費力。按照由簡(jian)至繁的(de)(de)原(yuan)則(ze)，維(wei)修人員(yuan)結合維(wei)修該(gai)車的(de)(de)經驗(yan)，此(ci)段線(xian)(xian)路(lu)一般不(bu)會出問(wen)題，所以(yi)維(wei)修人員(yuan)只是(shi)拆下(xia)熔絲(si)盒和雜物(wu)箱簡(jian)單地查(cha)(cha)看了一下(xia)，但(dan)沒有發現線(xian)(xian)路(lu)存在(zai)搭(da)鐵的(de)(de)情況。繼(ji)續檢查(cha)(cha)電(dian)(dian)(dian)子(zi)扇(shan)，可(ke)以(yi)確定是(shi)剛更換(huan)的(de)(de)新件(jian)，便仔細(xi)觀(guan)察(cha)發現該(gai)電(dian)(dian)(dian)子(zi)扇(shan)不(bu)是(shi)原(yuan)廠配件(jian)。會不(bu)會更換(huan)的(de)(de)電(dian)(dian)(dian)子(zi)扇(shan)質量有問(wen)題導致熔絲(si)被(bei)燒呢?由于旁邊有相同型號(hao)車輛，為了能夠快(kuai)速判斷，維(wei)修人員(yuan)對(dui)散熱器電(dian)(dian)(dian)子(zi)扇(shan)進(jin)(jin)行了替換(huan)試(shi)驗(yan)，試(shi)驗(yan)結果令人失望。至此(ci)，維(wei)修工作(zuo)陷入僵局(ju)。

此(ci)時維(wei)修人員仔細回顧了(le)(le)一(yi)下(xia)該車故(gu)(gu)障檢修的全過程(cheng)，并揣摩了(le)(le)一(yi)遍(bian)診斷思路和維(wei)修方(fang)法，并沒有想到哪兒有遺漏或不合理的地方(fang)。那么會不會是根據維(wei)修經驗判(pan)定沒問(wen)(wen)題的地方(fang)出了(le)(le)問(wen)(wen)題呢?于是維(wei)修人員拆下(xia)雜物箱，對其后部(bu)的配電(dian)(dian)(dian)盤進行仔細檢查(cha)發(fa)現(xian)(xian)，該車原(yuan)車的繼(ji)(ji)電(dian)(dian)(dian)器(qi)K70應(ying)該為一(yi)個(ge)黃色的繼(ji)(ji)電(dian)(dian)(dian)器(qi)，而(er)該車卻沒有那個(ge)黃色的繼(ji)(ji)電(dian)(dian)(dian)器(qi)，取而(er)代之的是一(yi)個(ge)普通的4腳黑色繼(ji)(ji)電(dian)(dian)(dian)器(qi)。會是這個(ge)4腳繼(ji)(ji)電(dian)(dian)(dian)器(qi)引(yin)發(fa)的故(gu)(gu)障嗎?維(wei)修人員先(xian)檢查(cha)了(le)(le)此(ci)黑色繼(ji)(ji)電(dian)(dian)(dian)器(qi)的插腳位置，但沒有發(fa)現(xian)(xian)插反的現(xian)(xian)象。為了(le)(le)確(que)定究(jiu)竟是不是這個(ge)黑色繼(ji)(ji)電(dian)(dian)(dian)器(qi)的問(wen)(wen)題，還是決定替換原(yuan)廠繼(ji)(ji)電(dian)(dian)(dian)器(qi)進行試驗。在更換原(yuan)車繼(ji)(ji)電(dian)(dian)(dian)器(qi)后，試車發(fa)現(xian)(xian)故(gu)(gu)障居然消失了(le)(le)。

那么(me)為(wei)(wei)什么(me)該(gai)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)會(hui)導(dao)致該(gai)車發(fa)生此(ci)(ci)故(gu)障(zhang)呢(ni)?為(wei)(wei)探求究竟，維修人員查閱(yue)了該(gai)車的(de)(de)(de)相(xiang)關電(dian)(dian)(dian)(dian)路圖。經查閱(yue)相(xiang)關維修資料并仔細(xi)分(fen)析電(dian)(dian)(dian)(dian)路圖可(ke)知，該(gai)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)非普通(tong)4腳(jiao)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)，而是(shi)(shi)(shi)一個(ge)延(yan)時(shi)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)。當(dang)滿(man)足電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)低(di)速(su)運(yun)轉(zhuan)條件(jian)時(shi)，2個(ge)電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)M11、M4由發(fa)動(dong)機控(kong)制(zhi)(zhi)(zhi)單(dan)元ECM控(kong)制(zhi)(zhi)(zhi)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K51的(de)(de)(de)觸(chu)(chu)點(dian)吸(xi)合(he)，經過K52的(de)(de)(de)常閉觸(chu)(chu)點(dian)，電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)M11、M4形成(cheng)串聯電(dian)(dian)(dian)(dian)路，2個(ge)電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)同時(shi)低(di)速(su)運(yun)轉(zhuan)；當(dang)滿(man)足2個(ge)電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)高速(su)運(yun)轉(zhuan)的(de)(de)(de)條件(jian)時(shi)，除(chu)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K51的(de)(de)(de)觸(chu)(chu)點(dian)吸(xi)合(he)外(wai)，發(fa)動(dong)機控(kong)制(zhi)(zhi)(zhi)單(dan)元ECM也將(jiang)控(kong)制(zhi)(zhi)(zhi)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K52的(de)(de)(de)觸(chu)(chu)點(dian)吸(xi)合(he)。由于(yu)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K51、K52的(de)(de)(de)觸(chu)(chu)點(dian)均(jun)吸(xi)合(he)，電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)M11直接形成(cheng)單(dan)獨的(de)(de)(de)搭鐵回路，于(yu)是(shi)(shi)(shi)實(shi)現高速(su)運(yun)轉(zhuan)。其實(shi)發(fa)動(dong)機控(kong)制(zhi)(zhi)(zhi)單(dan)元ECM此(ci)(ci)時(shi)也已經控(kong)制(zhi)(zhi)(zhi)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K70的(de)(de)(de)觸(chu)(chu)點(dian)吸(xi)合(he)，但因繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)K70內部的(de)(de)(de)延(yan)時(shi)電(dian)(dian)(dian)(dian)路作用(yong)(yong)，該(gai)繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)(de)觸(chu)(chu)點(dian)在3s后(hou)才會(hui)吸(xi)合(he)，電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)M4才會(hui)高速(su)運(yun)轉(zhuan)。之(zhi)所(suo)以采用(yong)(yong)這(zhe)樣的(de)(de)(de)設計電(dian)(dian)(dian)(dian)路，是(shi)(shi)(shi)因為(wei)(wei)這(zhe)樣可(ke)以避免電(dian)(dian)(dian)(dian)子(zi)扇(shan)(shan)高速(su)運(yun)轉(zhuan)時(shi)起動(dong)的(de)(de)(de)瞬間(jian)電(dian)(dian)(dian)(dian)流過大燒毀熔(rong)絲。到此(ci)(ci)，故(gu)障(zhang)終于(yu)水落(luo)石(shi)出。在更(geng)換(huan)新繼(ji)(ji)(ji)電(dian)(dian)(dian)(dian)器(qi)(qi)后(hou)，故(gu)障(zhang)排除(chu)。