BODY-05, Headlight Motor Circuit - Operation and Repair

Transcription

1 BODY-05, Headlight Mtr Circuit - Operatin and Repair Intrductin The fllwing prcedure, written by Dave Simms, is based n the headlight mtr circuits in 1983 and 1984 mdel 944s. Dave has als included infrmatin n hw the mtr circuits in later 944s differ frm thse f the early cars. Hwever, the thery f peratin and repair methds remain the same. I've added a few ntes alng the way and a different circuit diagram (with Dave's apprval). We plan t expand this prcedure dwn the rad t describe hw the entire exterir lighting circuit wrks in detail. But first, I have t figure ut exactly hw the bridge adapter in the later mdel 944 wrks. I'd like t thank Dave fr his valuable cntributin t Clark's Garage. Frewrd by the Authr Clark Fletcher My 944 had been reclaimed frm an insurance cmpany fllwing a vandalism claim. The car had gne t a yard where sme parts had been sld frm it. In the prcess, the wiring harness had been cut in the frnt f the car and the headlight mtr had been sld. When I purchased the car, the headlight mtr in it had cme frm anther wreck and was nt cnnected. The internal circuit under the relay blck had been rewired incrrectly. Finally, the mechanical headlight linkage was binding and several f the cap screws were lse. Surprisingly, mst f the car was fine. S far, I have rebuilt all f the brake calipers, resurfaced r replaced all f the rtrs, repacked the CV jints, fixed a number f electrical prblems and cured sme ills in the cling system. I have learned that ne f the mst imprtant things abut the 944 is the assrtment f clips and clamps that hld the varius tubes, wires and hses in place. When I gt the car, the tp rad hse was nt clamped in place. One result was the circular-saw effect that had been applied by the alternatr pulley t the hse. Cars that have seen wrk dne by a number f different peple may be subject t slppiness in the area f what appears t be unimprtant details. I'm resigned t the fact that, if I want a reliable car, the details must be identical t the way they were when the car left the factry. All tld, I am enjying wrking thrugh the varius systems f the 944, checking and rebuilding them. The car is different and my wrk has been an educatin. I have strived t d every task, by the bk. Restring the car's perfrmance and reliability is my aim. David Simms, Kamlps, BC, Canada Page 1 f 7

2 Prsche 944 Headlight Mtr Circuit, Operatin and Repair Cmpnents Mtr Wrm gear / Rtary Switch : This switch has three brushes which ride n a cnducting disk. The inner brush has a cut-ut that interrupts the current when the headlights have reached the ff psitin. The center brush has an uninterrupted path. The utside brush has a cut-ut that interrupts the current when the headlights have reached the n psitin. Relay This nrmally-ff relay cntrls the mtr. Uses Red/Blue cnductr. Fur Cnductrs: Cntrl wires :Grey, Red/Green. Supply wire :Red/Blue. Grund Wire : Brwn. S1 Nrmally-n switch, cntrlled by the headlight dash switch. Uses Red/Green cnductr. S2 Nrmally-ff switch, same as abve. Uses Grey cnductr. Dash Light Switch cntrls S1 and S2. Page 2 f 7

3 Thery f Operatin Initially, the ignitin switch is n and the headlights are ff. S1 is clsed and the red/green cnductr has 12 vlts n it. The inner brush f the rtary switch resides n its cut-ut. N current flws t the relay cil. The dash headlight switch is turned t n. Switch S1 is turned ff (n effect). S2 is turned n, the grey cnductr ges frm zer t 12 vlts. The utside brush n the rtary switch allws current t energize the relay cil. The relay clses the cntact allwing current t flw alng Red/Blue t the mtr. The mtr perates until the utside brush in the rtary switch meets its cut-ut. Current t the relay is nw interrupted. The mtr turns ff. The headlights are nw in their n psitin. NOTE The first psitin n the headlight switch turns n the parking and license plate lights. The secnd psitin n the switch turns n the headlights and energizes the cncealing mtr t raise the headlights. C.F. The grey cnductr still has 12 vlts and the Red/green ne has 0 vlts. The dash headlight switch is nw turned t the ff psitin. S2 pens and S1 clses. The grey cnductr ges t 0 vlts, the Red/green ne t 12 vlts. The inner brush n the rtary switch energizes the relay cil. The mtr perates until the inner brush tuches its cut-ut, turning ff the relay and the mtr. The headlights are nw in their ff psitin. This cmpletes ne cycle f headlight mtr peratin. NOTE If yu've ever tried t perate raise the headlights manually, yu prbably fund that when yu reached a certain pint raising the headlights that they autmatically went back dwn. That's because the headlight cncealing mtr energizes t bth raise and lwer the headlights. As yu rtate the dial n the mtr, yu als mve the rtary switch. With the S1 switch clsed, when the rtary switch cntact is made, the mtr energizes and returns t the clsed psitin. If yu wish t raise the headlights manually, yu must remve Fuse #1 n the auxiliary fuse panel fr early 944s r Fuse #2 n the main fuse panel fr later mdel 944s. C.F. Page 3 f 7

4 Ntes Regarding the /2 and mre Recent Mdels Similarities & Differences Between Early/Late Mdels: Basic principles f Operatin are the Same The Grey cntrl wire is nw Yellw/Blue The cntrl wires are nw fused The Red/Green wire requires a 7.5 A fuse in hlder n.16 The Yellw/Blue wire takes a 7.5 A fuse in hlder n.37 The Red/Blue supply wire takes a 25 A fuse in hlder n. 2 These fuses must be checked befre undertaking any repairs Maintenance Suggestins If the car is new-t-yu, check the fuse values: 16 amps in the n. 1 fuse hlder n the Additinal Fuse Bx (Early 944s). Fr later cars, check the three fuses listed abve. Turn the manual cntrl knb n the headlight mtr t take the system thrugh ne cycle, nte any pints f excessive resistance. Remember t remve the mtr fuses befre trying t cycle the mtr manually. Try t lcate where the rubbing ccurs. It will prbably ccur where the headlight assembly passes thrugh the bdywrk. Yu may need t remve freign material. Or, yu may need t adjust the alignment f the linkage. Nte the sheet metal tabs n either side f the car abve the radiatr. On each tab are three small cap screws. Yu can make small adjustments t the linkage here. Yur car may have sustained frnt-end damage and flds in the bdy metal may be rubbing n the headlight husings as they change psitin. Cnsult a bdy man if this is preventing the prper peratin f the headlight linkage. Grease the ball-jints in the linkage with lithium-based grease. Prper lubricatin will make a surprising difference in the resistance encuntered by the headlight cncealing mtr. Page 4 f 7

5 Repair Prcedures Headlights t lw r t high Start the car. Turn n the headlights. Unscrew the linkage frm the mtr shaft withut turning it. Repsitin the headlights manually while hlding the linkage that yu just remved frm the mtr. Recnnect the linkage t the mtr shaft. Try turning the headlights n / ff nce mre t verify the crrect psitin. Repeat the prcedure, if necessary. Headlights turn n but d nt mve Check Fuses. On the '85 1/2 and later mdels, the cntrl wires are fused t. The headlight mtr assembly will prbably have t be remved frm the car. First, discnnect the 4-pin cnnectr t the mtr. Check the vltages n the cnductrs. Mtr r ignitin n Light switch ff. Brwn and grey: 0 vlts, Red/Green and Red/Blue: 12 vlts Mtr r ignitin n Light switch n. Brwn and Red/Green: 0 vlts. Grey and Red/Blue: 12 vlts. Mtr r ignitin ff Light switchff. Brwn and grey : 0 vlts. Red/Green and Red/Blue : 12 vlts. If the vltages are nt as abve, the prblem lies in the headlight relay r dash switch. Remve and check them with an hmmeter. Check the cntinuity f the cnductrs. Have fun!! If the vltages have the prescribed values, remve the mtr assembly. The unit will have t be bench-tested. Bench-testing the mtr unit Remve unit frm car. Discnnect mtr shaft frm linkage. Remve fur-pin electrical cnnectr frm mtr assembly Remve the three screws hlding the unit t the car Remve the rubber cvers frm the mtr assembly D a visual/electrical check f cmpnents Check cnditin f the relay pints. If they are burned, file the pints r replace the relay. Check cntinuity f relay cil with an hmmeter. The wire is fine and can easily break. The resistance f the cil is abut 65 Ohms. If there is n cntinuity, the relay will need t be replaced. If the abve checks ut all right, remve the relay blck frm the mtr. Check the male and female cnnectrs in the fur-pin cnnectr fr damage. Yu may need t bring the unit t yur lcal supplier t get cmpatible cnnectrs if they are damaged. Page 5 f 7

6 Check wiring f the relay blck. terminals 1 & 3: T mtr and Red/Blue. terminals 2 & 5: T the relay cil, frm grund and center brush n rtary switch terminal 5: N cnnectin. Remve the rtary switch cver and check the brushes. If a brush is damaged, it can be remved by de-sldering it frm the external wire. Yu may be able t get a replacement frm an appliance repairman r t fashin ne frm a piece f flat brass. The amunt f current flwing thrugh these brushes is negligible if everything is wrking prperly. Therefre, the cnstructin f these brushes, apart frm their length, is nt critical. Test the mtr This is prbably the least likely area f failure. Remve the mtr relay frm the relay blck by prying gently with a screwdriver. Fit a spade-type female cnnectr t a piece f wire and insert it int the relay side f terminal 1 r 3 (whichever will cnnect t the green mtr wire). Cnnect the case f the mtr t the negative terminal f a battery r battery charger and the ther wire t the psitive terminal. If the mtr des nt turn, lk fr a pr cnnectin, therwise, a new mtr is required. Page 6 f 7

7 Repairing the rubber bts. With time and temperature changes, the rubber bts prtecting yur headlight mtr may have split alng their seams. Clean and lightly sand the areas adjining the split. Apply tape t the inside f the split s that the bt is held tgether. Apply several layers f autmtive GOOP t the split, allwing each layer t dry befre applying the next. Remve the tape and apply layers f GOOP t the inside f the split. Trim ff any excess. Yur bt shuld be able t withstand sme vigrus stretching as it is put back n the mtr. Clark s Garage 1998 Page 7 f 7