home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > maintenance & nonperformance

Reply
 
Thread Tools Display Modes
Old 12-10-2006, 09:12 AM   #1
ediaz
Board Member
 
Join Date: May 2005
Thumbs down electrical nihgtmare no guages,no charge

1991 740 turbo the tach.,speed & gas guage stopped working, and now the charging system works sometimes.I did'nt know where to start so I checked all fuses.their ok, I checked the relays behind the fuses they all seem to be ok, I checked them by changing them one by one with another set I have from another 740 I have I cleaned the batterie teminals and charged the batterie, and I checked the grounds under the hood they seem all good. I also checked the conection to the alternator again all good.I tryed another ignition switch no help.Please someone help me.
ediaz is offline   Reply With Quote
Old 12-10-2006, 09:18 AM   #2
Unregistered
Guest
 
Default

Quote:
Originally Posted by ediaz View Post
1991 740 turbo the tach.,speed & gas guage stopped working, and now the charging system works sometimes.I did'nt know where to start so I checked all fuses.their ok, I checked the relays behind the fuses they all seem to be ok, I checked them by changing them one by one with another set I have from another 740 I have I cleaned the batterie teminals and charged the batterie, and I checked the grounds under the hood they seem all good. I also checked the conection to the alternator again all good.I tryed another ignition switch no help.Please someone help me.
http://www.brickboard.com/FAQ/700-90...Intermittently
  Reply With Quote
Old 12-10-2006, 11:20 AM   #3
derosa
The Rev
 
derosa's Avatar
 
Join Date: Mar 2003
Location: Wolcott, NY
Default

The alt requires the battery light in the dash to work, the light is a sort of ground, when the key is partially on it gets a charge from the battery which flows through to I believe the voltage regulator, once the car is running that charge tells the alt to start putting out power which it does turning the light off. If the dash doesn't work allowing the light to create the curcuit then the alt doesn't charge. There is an over ride of revving the car to 4 or 5k rpms, I remember when working on my dash it revved the engine pretty loud so I suspect 5k just can't remember.
__________________
98 v70xc running, needs an m66 and full stage 0.
98 v70 5spd- RIP
91 240 +T - RIP, it was fun while it lasted.
79 262c, still currently under construction, but now actually under active construction.


Cuius testiculos habes, habeas cardia et cerebellum.
derosa is offline   Reply With Quote
Old 12-11-2006, 01:24 AM   #4
ediaz
Board Member
 
Join Date: May 2005
Default

I pulled out the instrument cluster and found the screws loose and one broken wire.I soldered it and replaced the instr. clucter and works normal.Thanks for the help.
ediaz is offline   Reply With Quote
Old 12-11-2006, 02:48 AM   #5
clipster
Board Member
 
clipster's Avatar
 
Join Date: Sep 2006
Location: CrapLanta
Default

Are you freakin kidding me?

Man and I thought useless information went the way of Britney Spears shacking up with Madonna... dude, this is quite bizarre! The Charging system depends on the INSTRUMENT CLUSTER???

WOW. All these years and I never knew! What a load of crap, but I'm glad that someone else had this problem before I did! Thanks for this post, a million times in advance!
clipster is offline   Reply With Quote
Old 12-11-2006, 03:27 AM   #6
ADent
Board Member
 
Join Date: Feb 2003
Location: Denver, Colorado
Default

That's the way it works.

From wiki:
Quote:
The voltage regulator operates by modulating the small field current in order to produce a constant voltage at the stator output. In many older designs of car, the field windings are initially supplied via the ignition switch and charge warning light, which is why the light glows when the ignition is on but the engine is not running. Once the engine runs and the alternator is generating, a diode feeds the field current from the alternator main output, thus equalizing the voltage across the warning light which goes out. The wire supplying the field current is often referred to as the "exciter" wire.

.. snip

One drawback of this arrangement is that if the warning light fails or the "exciter" wire is disconnected, no priming current reaches the alternator field windings and so the alternator will not generate any power. However, some alternators will self-excite when the engine is revved to a certain speed. The driver may check for a faulty exciter-circuit by ensuring that the warning light is glowing with the engine stopped.
ADent is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 06:11 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.