一、汽車發電機不發電是怎么回事

汽車(che)交流(liu)(liu)發(fa)電(dian)機(ji)正常發(fa)電(dian)，必(bi)須(xu)(xu)具備兩個條件(jian)： 一(yi)是(shi)勵磁電(dian)路、定(ding)子繞組電(dian)路和整流(liu)(liu)器必(bi)須(xu)(xu)工(gong)作正常； 二(er)是(shi)交流(liu)(liu)發(fa)電(dian)機(ji)轉子必(bi)須(xu)(xu)旋轉。汽車(che)發(fa)電(dian)機(ji)不發(fa)電(dian)可(ke)能(neng)是(shi)某些零(ling)部件(jian)出現了問題，以下是(shi)常見(jian)的(de)汽車(che)發(fa)電(dian)機(ji)不發(fa)電(dian)的(de)原因(yin)：

1、二極管擊穿(chuan)，不起整(zheng)流作用。

2、電(dian)刷在電(dian)刷架內卡住，發電(dian)機因不勵磁而不能發電(dian)。

3、轉子的(de)(de)(de)磁場(chang)線(xian)(xian)(xian)(xian)圈(quan)(quan)不通(tong)電：轉子線(xian)(xian)(xian)(xian)圈(quan)(quan)的(de)(de)(de)折疊(die)層數多，部(bu)分線(xian)(xian)(xian)(xian)圈(quan)(quan)在浸絕緣漆(qi)時，沒有浸到(dao)線(xian)(xian)(xian)(xian)圈(quan)(quan)底(di)(di)層中去，底(di)(di)層線(xian)(xian)(xian)(xian)圈(quan)(quan)匝與匝之間(jian)存(cun)在一定(ding)的(de)(de)(de)間(jian)隙。隨著發動機(ji)轉速的(de)(de)(de)變(bian)化，底(di)(di)層線(xian)(xian)(xian)(xian)圈(quan)(quan)將存(cun)在不同的(de)(de)(de)離心力。線(xian)(xian)(xian)(xian)圈(quan)(quan)收縮、膨脹的(de)(de)(de)頻率(lv)，決定(ding)了線(xian)(xian)(xian)(xian)圈(quan)(quan)和引線(xian)(xian)(xian)(xian)角(jiao)度大小變(bian)換的(de)(de)(de)次數，常(chang)見磁場(chang)線(xian)(xian)(xian)(xian)圈(quan)(quan)到(dao)滑環的(de)(de)(de)引線(xian)(xian)(xian)(xian)，特別是底(di)(di)層線(xian)(xian)(xian)(xian)圈(quan)(quan)的(de)(de)(de)引線(xian)(xian)(xian)(xian)使用過久，將產生金屬疲(pi)勞而折斷。

4、定子線圈相間短(duan)路或(huo)搭鐵。

5、轉子(zi)的爪極(ji)松動(dong)：若在(zai)(zai)軸上(shang)稍有松動(dong)，則爪極(ji)內端(duan)面與磁(ci)(ci)鐵(tie)端(duan)面之間就會有間隙(xi)產生(sheng)，磁(ci)(ci)場(chang)線圈(quan)產生(sheng)的磁(ci)(ci)通就會在(zai)(zai)此漏(lou)掉，導致定子(zi)的磁(ci)(ci)通大大減少，定子(zi)線圈(quan)感應的電動(dong)勢也因此大大減小(xiao)，以致于不能產生(sheng)足夠的電壓(ya)對蓄電池進行(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(che)發電(dian)機故(gu)(gu)障(zhang)時(shi)，可以(yi)不拆卸發電(dian)機，在車(che)上對其(qi)檢測，概略判(pan)斷(duan)是否有故(gu)(gu)障(zhang)。

（1）萬用表電壓檔檢測

將(jiang)萬用表旋鈕旋至直流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)(ya)30V檔(dang)（或用一般(ban)的直流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)(ya)表適當檔(dang)），把紅表筆接發電(dian)(dian)(dian)機(ji)(ji)“電(dian)(dian)(dian)樞(shu)”接柱(zhu)，黑表筆接外殼(ke)，讓發動機(ji)(ji)運轉在中速以上(shang)，12V電(dian)(dian)(dian)氣系統(tong)的電(dian)(dian)(dian)壓(ya)(ya)(ya)標準值應(ying)在14V左(zuo)(zuo)右，24V電(dian)(dian)(dian)氣系統(tong)的電(dian)(dian)(dian)壓(ya)(ya)(ya)標準值應(ying)在28V左(zuo)(zuo)右。若(ruo)測的電(dian)(dian)(dian)壓(ya)(ya)(ya)為(wei)蓄電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)(ya)，則(ze)表明發電(dian)(dian)(dian)機(ji)(ji)不發電(dian)(dian)(dian)。

（2）外接電流表檢測

當(dang)汽車儀表(biao)(biao)(biao)板上(shang)沒有電(dian)(dian)(dian)(dian)流表(biao)(biao)(biao)時(shi)，可用(yong)外(wai)接(jie)(jie)直(zhi)流電(dian)(dian)(dian)(dian)流表(biao)(biao)(biao)來(lai)檢測。先把(ba)發電(dian)(dian)(dian)(dian)機(ji)“電(dian)(dian)(dian)(dian)樞”接(jie)(jie)柱導線拆(chai)(chai)下，再(zai)將量(liang)程為20A左右(you)的直(zhi)流電(dian)(dian)(dian)(dian)流表(biao)(biao)(biao)正(zheng)極接(jie)(jie)發電(dian)(dian)(dian)(dian)機(ji)“電(dian)(dian)(dian)(dian)樞”，負極導線接(jie)(jie)上(shang)述拆(chai)(chai)下接(jie)(jie)頭。當(dang)發動機(ji)在(zai)中(zhong)速以上(shang)運(yun)轉（不使用(yong)其他電(dian)(dian)(dian)(dian)器設備）時(shi)，電(dian)(dian)(dian)(dian)流表(biao)(biao)(biao)有3A~5A充電(dian)(dian)(dian)(dian)指示，表(biao)(biao)(biao)明發電(dian)(dian)(dian)(dian)機(ji)工作(zuo)正(zheng)常，否則發電(dian)(dian)(dian)(dian)機(ji)不發電(dian)(dian)(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。將燈泡兩端焊接(jie)適當(dang)長度(du)的(de)(de)導(dao)線(xian)，并在其兩端接(jie)上(shang)鍔(e)魚夾。檢測前先將(jiang)發電機“電樞”接(jie)柱的(de)(de)導(dao)線(xian)拆下，再將(jiang)試燈(deng)的(de)(de)一端夾住發電機“電樞”接(jie)柱，另(ling)一端搭(da)鐵，當(dang)發動機中(zhong)速運轉時，試燈(deng)亮度(du)說明發電機工(gong)作正常，否則發電機不發電。

（4）改變發動機轉速、觀察大燈亮度法

起動(dong)發動(dong)機后，打(da)開大燈，讓發動(dong)機轉速從(cong)怠速逐漸提(ti)高(gao)到(dao)中(zhong)等轉速，大燈的亮度若隨轉速的提(ti)高(gao)而增加，說明發電機工作正常，否(fou)則為(wei)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(wei)機控制(zhi)電子(zi)裝置時，可以用此種方法檢測(ce)。把發動(dong)機控制(zhi)在(zai)中速以上(shang)，拆下蓄電池搭(da)鐵線(xian)（一般(ban)是斷開蓄電池搭(da)鐵線(xian)上(shang)的控制(zhi)總開關），若發動(dong)機工作(zuo)正(zheng)常，說(shuo)明(ming)發電機發電，否則發電機有故障。

2、車下不解體檢測與判斷

維修汽車發(fa)電機(ji)故障(zhang)也可以選擇從車上(shang)拆下發(fa)電機(ji)后，用下述(shu)方(fang)法檢(jian)查，進一步確定故障(zhang)。

（1）用小燈泡（手電燈泡）判斷

把(ba)手(shou)電(dian)(dian)(dian)(dian)燈泡的(de)兩(liang)端接(jie)(jie)上(shang)導線(xian)做成小(xiao)試燈，接(jie)(jie)于發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機“電(dian)(dian)(dian)(dian)樞(shu)”和外殼之間。用導線(xian)將蓄電(dian)(dian)(dian)(dian)池(chi)（或相同電(dian)(dian)(dian)(dian)壓的(de)干(gan)電(dian)(dian)(dian)(dian)池(chi)）正、負極(ji)分別連接(jie)(jie)在發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機的(de)兩(liang)磁場接(jie)(jie)柱“F1”、“F2”（內搭鐵(tie)的(de)交流發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機接(jie)(jie)“F”和“搭鐵(tie)”接(jie)(jie)柱）上(shang)，讓(rang)蓄電(dian)(dian)(dian)(dian)池(chi)給(gei)發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機激磁。用手(shou)快速轉動(dong)發(fa)(fa)(fa)動(dong)機皮帶盤，小(xiao)試燈說明發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機工作正常，否則發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)機不(bu)發(fa)(fa)(fa)電(dian)(dian)(dian)(dian)。

（2）萬用表電壓檔判斷

讓蓄電(dian)(dian)(dian)池給發(fa)電(dian)(dian)(dian)機激磁(ci)（接(jie)(jie)線方(fang)法同2．1），將萬用表選擇在直(zhi)(zhi)流電(dian)(dian)(dian)壓(ya)3－5V（或(huo)(huo)一般直(zhi)(zhi)流電(dian)(dian)(dian)壓(ya)表適當檔(dang)）檔(dang)，黑、紅表筆分別(bie)接(jie)(jie)“搭鐵”和發(fa)電(dian)(dian)(dian)機“電(dian)(dian)(dian)樞”接(jie)(jie)柱，用手轉(zhuan)動皮帶盤(pan)，萬用表（或(huo)(huo)直(zhi)(zhi)流電(dian)(dian)(dian)壓(ya)表）指針應有(you)擺動，否(fou)則(ze)發(fa)電(dian)(dian)(dian)機不發(fa)電(dian)(dian)(dian)。

（3）萬用表電阻檔檢測與判斷

用萬(wan)用表R×1電(dian)(dian)阻(zu)檔，測量各接線柱之間(jian)的(de)電(dian)(dian)阻(zu)（不同型(xing)號發電(dian)(dian)機(ji)的(de)電(dian)(dian)阻(zu)值(zhi)不同，下表為(wei)JF522A型(xing)發電(dian)(dian)機(ji)）值(zhi)，與正(zheng)常(chang)值(zhi)比較，可以判斷出(chu)發電(dian)(dian)機(ji)是否有故障。

（4）示波器法檢測與判斷

將(jiang)發(fa)電(dian)機裝在電(dian)器試驗臺(tai)上(shang)，連接好示波器與發(fa)電(dian)機之(zhi)間的(de)導線(xian)，把發(fa)電(dian)機控(kong)制在中等轉速，發(fa)電(dian)機正常工作及各(ge)種故障所對應的(de)電(dian)壓(ya)波形。