一、汽車發電機不發電是怎么回事

汽(qi)車(che)交(jiao)流發(fa)電(dian)(dian)(dian)機(ji)正常(chang)發(fa)電(dian)(dian)(dian)，必(bi)須具備兩(liang)個條件(jian)： 一是勵(li)磁電(dian)(dian)(dian)路、定子繞(rao)組電(dian)(dian)(dian)路和整流器必(bi)須工作正常(chang)； 二是交(jiao)流發(fa)電(dian)(dian)(dian)機(ji)轉子必(bi)須旋轉。汽(qi)車(che)發(fa)電(dian)(dian)(dian)機(ji)不(bu)發(fa)電(dian)(dian)(dian)可能是某些零部件(jian)出現了問題(ti)，以下是常(chang)見的汽(qi)車(che)發(fa)電(dian)(dian)(dian)機(ji)不(bu)發(fa)電(dian)(dian)(dian)的原因：

1、二極(ji)管擊(ji)穿，不起整(zheng)流(liu)作用。

2、電刷(shua)在電刷(shua)架內卡住，發(fa)電機因不(bu)勵磁而不(bu)能發(fa)電。

3、轉(zhuan)子的(de)(de)(de)磁場線(xian)(xian)(xian)圈(quan)(quan)不(bu)通(tong)電：轉(zhuan)子線(xian)(xian)(xian)圈(quan)(quan)的(de)(de)(de)折(zhe)疊層(ceng)(ceng)數多，部(bu)分(fen)線(xian)(xian)(xian)圈(quan)(quan)在(zai)浸絕(jue)緣漆時，沒有(you)浸到線(xian)(xian)(xian)圈(quan)(quan)底層(ceng)(ceng)中去，底層(ceng)(ceng)線(xian)(xian)(xian)圈(quan)(quan)匝與匝之(zhi)間存(cun)在(zai)一定的(de)(de)(de)間隙。隨著發(fa)動機轉(zhuan)速的(de)(de)(de)變化，底層(ceng)(ceng)線(xian)(xian)(xian)圈(quan)(quan)將存(cun)在(zai)不(bu)同的(de)(de)(de)離心力。線(xian)(xian)(xian)圈(quan)(quan)收(shou)縮、膨脹的(de)(de)(de)頻率，決定了線(xian)(xian)(xian)圈(quan)(quan)和(he)引線(xian)(xian)(xian)角度(du)大小變換的(de)(de)(de)次(ci)數，常見磁場線(xian)(xian)(xian)圈(quan)(quan)到滑環的(de)(de)(de)引線(xian)(xian)(xian)，特別是底層(ceng)(ceng)線(xian)(xian)(xian)圈(quan)(quan)的(de)(de)(de)引線(xian)(xian)(xian)使用過久，將產生金屬疲勞而折(zhe)斷。

4、定子線圈相間短路或搭(da)鐵。

5、轉子(zi)的爪極松動(dong)：若在軸上稍有(you)松動(dong)，則爪極內端面(mian)(mian)與磁(ci)(ci)(ci)鐵端面(mian)(mian)之(zhi)間(jian)就(jiu)(jiu)會(hui)(hui)有(you)間(jian)隙產(chan)(chan)生(sheng)(sheng)，磁(ci)(ci)(ci)場線圈產(chan)(chan)生(sheng)(sheng)的磁(ci)(ci)(ci)通(tong)就(jiu)(jiu)會(hui)(hui)在此漏(lou)掉(diao)，導致(zhi)定子(zi)的磁(ci)(ci)(ci)通(tong)大(da)大(da)減少，定子(zi)線圈感應的電動(dong)勢(shi)也因此大(da)大(da)減小，以致(zhi)于不能產(chan)(chan)生(sheng)(sheng)足(zu)夠的電壓對(dui)蓄電池進行(xing)充(chong)電。

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二、汽車電機不發電故障如何檢修

1、就車檢測法

汽車發電(dian)機(ji)故(gu)障(zhang)時，可以(yi)不拆卸發電(dian)機(ji)，在車上對其檢測，概略判斷是否(fou)有故(gu)障(zhang)。

（1）萬用表電壓檔檢測

將(jiang)萬(wan)用(yong)(yong)表(biao)(biao)(biao)(biao)旋鈕旋至(zhi)直(zhi)流(liu)電(dian)壓(ya)(ya)30V檔(dang)（或用(yong)(yong)一般的(de)直(zhi)流(liu)電(dian)壓(ya)(ya)表(biao)(biao)(biao)(biao)適當檔(dang)），把紅表(biao)(biao)(biao)(biao)筆(bi)接發(fa)電(dian)機“電(dian)樞”接柱，黑(hei)表(biao)(biao)(biao)(biao)筆(bi)接外殼，讓發(fa)動機運轉在(zai)中速(su)以上，12V電(dian)氣(qi)系(xi)統(tong)的(de)電(dian)壓(ya)(ya)標準(zhun)值(zhi)應(ying)在(zai)14V左(zuo)右，24V電(dian)氣(qi)系(xi)統(tong)的(de)電(dian)壓(ya)(ya)標準(zhun)值(zhi)應(ying)在(zai)28V左(zuo)右。若測的(de)電(dian)壓(ya)(ya)為(wei)蓄電(dian)池(chi)電(dian)壓(ya)(ya)，則表(biao)(biao)(biao)(biao)明發(fa)電(dian)機不(bu)發(fa)電(dian)。

（2）外接電流表檢測

當汽車儀表(biao)(biao)板(ban)上(shang)沒有電(dian)(dian)流(liu)(liu)表(biao)(biao)時，可用(yong)外接(jie)直流(liu)(liu)電(dian)(dian)流(liu)(liu)表(biao)(biao)來檢測。先(xian)把發(fa)電(dian)(dian)機(ji)“電(dian)(dian)樞”接(jie)柱導(dao)線拆下(xia)，再將(jiang)量程為20A左右(you)的直流(liu)(liu)電(dian)(dian)流(liu)(liu)表(biao)(biao)正(zheng)極接(jie)發(fa)電(dian)(dian)機(ji)“電(dian)(dian)樞”，負極導(dao)線接(jie)上(shang)述拆下(xia)接(jie)頭。當發(fa)動機(ji)在中(zhong)速以上(shang)運轉（不使用(yong)其他電(dian)(dian)器設(she)備(bei)）時，電(dian)(dian)流(liu)(liu)表(biao)(biao)有3A~5A充電(dian)(dian)指示，表(biao)(biao)明發(fa)電(dian)(dian)機(ji)工作(zuo)正(zheng)常(chang)，否(fou)則發(fa)電(dian)(dian)機(ji)不發(fa)電(dian)(dian)。

（3）試燈（汽車燈泡）法

當沒有萬用表和直流電表時，可用汽車燈泡做一試燈來檢測。將燈泡兩端(duan)(duan)焊接適當長度的(de)導(dao)線，并(bing)在其兩端(duan)(duan)接上鍔魚夾(jia)。檢(jian)測前先將發電機(ji)“電樞(shu)”接柱的(de)導(dao)線拆下，再將試(shi)燈的(de)一端(duan)(duan)夾(jia)住發電機(ji)“電樞(shu)”接柱，另一端(duan)(duan)搭(da)鐵(tie)，當發動機(ji)中速運(yun)轉時，試(shi)燈亮度說明(ming)發電機(ji)工作正常，否則發電機(ji)不發電。

（4）改變發動機轉速、觀察大燈亮度法

起動(dong)發動(dong)機(ji)后(hou)，打開大燈(deng)，讓(rang)發動(dong)機(ji)轉(zhuan)速(su)(su)從怠速(su)(su)逐漸提(ti)高到(dao)中等轉(zhuan)速(su)(su)，大燈(deng)的亮度若隨轉(zhuan)速(su)(su)的提(ti)高而增加，說(shuo)明發電機(ji)工作正常，否則為不發電。

（5）拆下蓄電池搭鐵看發動機（汽油機）是否工作法

當車上(shang)沒有微機控(kong)制電(dian)(dian)(dian)(dian)子裝(zhuang)置時，可(ke)以用此(ci)種(zhong)方法檢測。把發(fa)動機控(kong)制在中速以上(shang)，拆下蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)搭(da)鐵(tie)線（一般(ban)是斷開(kai)蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)搭(da)鐵(tie)線上(shang)的控(kong)制總(zong)開(kai)關），若發(fa)動機工(gong)作正常，說明發(fa)電(dian)(dian)(dian)(dian)機發(fa)電(dian)(dian)(dian)(dian)，否則(ze)發(fa)電(dian)(dian)(dian)(dian)機有故障。

2、車下不解體檢測與判斷

維修汽(qi)車發(fa)電(dian)機(ji)故障(zhang)也可以選擇從車上拆下發(fa)電(dian)機(ji)后，用下述方法(fa)檢查，進(jin)一步確定故障(zhang)。

（1）用小燈泡（手電燈泡）判斷

把(ba)手電(dian)燈泡的兩端接(jie)上導線做成小試(shi)燈，接(jie)于(yu)發(fa)電(dian)機“電(dian)樞(shu)”和(he)外殼之間(jian)。用(yong)導線將(jiang)蓄電(dian)池（或相(xiang)同(tong)電(dian)壓的干電(dian)池）正、負極分別(bie)連接(jie)在(zai)發(fa)電(dian)機的兩磁場接(jie)柱“F1”、“F2”（內搭鐵的交流發(fa)電(dian)機接(jie)“F”和(he)“搭鐵”接(jie)柱）上，讓蓄電(dian)池給發(fa)電(dian)機激(ji)磁。用(yong)手快速轉動發(fa)動機皮帶(dai)盤(pan)，小試(shi)燈說明發(fa)電(dian)機工作正常(chang)，否則發(fa)電(dian)機不發(fa)電(dian)。

（2）萬用表電壓檔判斷

讓蓄電(dian)(dian)(dian)池給(gei)發(fa)電(dian)(dian)(dian)機激(ji)磁（接(jie)線方(fang)法同2．1），將萬用表選擇在(zai)直流電(dian)(dian)(dian)壓3－5V（或一(yi)般直流電(dian)(dian)(dian)壓表適當檔）檔，黑(hei)、紅(hong)表筆分別接(jie)“搭鐵”和發(fa)電(dian)(dian)(dian)機“電(dian)(dian)(dian)樞”接(jie)柱，用手轉動(dong)皮帶盤，萬用表（或直流電(dian)(dian)(dian)壓表）指針應有(you)擺動(dong)，否(fou)則發(fa)電(dian)(dian)(dian)機不(bu)發(fa)電(dian)(dian)(dian)。

（3）萬用表電阻檔檢測與判斷

用萬用表(biao)R×1電(dian)(dian)(dian)(dian)阻檔(dang)，測量(liang)各接(jie)線柱之間的(de)(de)電(dian)(dian)(dian)(dian)阻（不同型(xing)號發(fa)電(dian)(dian)(dian)(dian)機(ji)的(de)(de)電(dian)(dian)(dian)(dian)阻值不同，下表(biao)為JF522A型(xing)發(fa)電(dian)(dian)(dian)(dian)機(ji)）值，與正常(chang)值比較，可以判斷出發(fa)電(dian)(dian)(dian)(dian)機(ji)是否(fou)有(you)故(gu)障(zhang)。

（4）示波器法檢測與判斷

將發電(dian)(dian)機裝(zhuang)在電(dian)(dian)器試驗臺(tai)上，連(lian)接好示波器與(yu)發電(dian)(dian)機之間的導線，把發電(dian)(dian)機控(kong)制在中等轉速(su)，發電(dian)(dian)機正常工作及各種故障所對應(ying)的電(dian)(dian)壓波形。