temp/gauge and sensor questions - BMW Forum - BimmerWerkz.com
3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

 
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#1 (permalink) Old 06-24-2008, 01:12 PM
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temp/gauge and sensor questions

1985 325e
ok my biggest thing is trying to find out where these items are housed and what their purpose is and perhaps what their relationship if any is.

water temp sensor.<<housed on thermostat housing. blue connector 2 poles
thermo fan switch<<housed on thermostat housing 2 spade connector
thermo time switch<<house behind thermostat housing near valve cover 2 pole connector
temp sending gauge switch<<< 1 spade connector housed on thermostat housing
water temp sender<<1 pole (brown connector) housed ???

if anyone knows the realtionship between these units and eachother or in relationship to the idle control module, I would be greatly appreciative of any passed on knowledge.
my gauge is currently reading but not reading accurately its a whole 1/4 off.
i disconnected the temp sending gauge switch and it just completely went off. so i figure this is the culprit. any other thoughts or suggestions?
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#2 (permalink) Old 06-25-2008, 09:02 PM
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Lightbulb

rehash: ;-)

the BLUE CONNECTOR- that is your THERMAL TIME SWITCH (wires=black-red/black-yellow) connects to Injection Control

the BROWN CONNECTOR- that is your temp sender. ( *note: it has only 1 wire. Disconnected, your temp dash meter read zero. If you ground the wire, your temp meter should be in the red zone)

on the thermostat head, you will also find the COOLANT TEMP SENSOR. (wires=green-red/brown) connects to Injection Control & Idle speed control module

the other sensor on your t-stat head is the EVAP TEMP SWITCH(wires= violet/black-white) connects to idle speed control module and A/C

TIP: check fuse #9... that is your idle control/vacuum advance fuse.

interrelation/s:
THERMO TIME SWITCH dictates idle control to be at higher RPM on start-up and bumps down the higher RPM to normal operating RPM once an acceptable operating temp is reached

COOLANT TEMP SENSOR communicated to the injection brain, the ambient temp of your engine... in order that your cold start injector can activate; and also increase idle via your idle speed control module during cold temps and on start-up

* correlatively, you have a zero degree temp switch mounted on your firewall that works in conjunction with your coolant temp sensor(wires green-yellow/blue-green) same operation... at lower temps, it will work on your injection brain and idle speed module to raise RPM.

EVAP TEMP SWITCH is connected to your Idle Speed Control Module and responsible for the "idle-up" functions when you turn on your A/C.

TEMP SENDING UNIT works independently and connects to your guage & an input voltage.

Last edited by darkhorse737; 06-25-2008 at 09:28 PM.
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#3 (permalink) Old 06-26-2008, 03:56 PM
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darkhorse your a source of unlimited knowledge haha. thank you sincerely.

i figure i shorted the temp sending unit and now i need to replace the temp gauge sending unit. what input voltage does it hook up too???<<<what is that refering too

also on a different note... does the idle control module have an ignition supply control??
cause im still trying to get the car to idle. and i have boght a new valve and a new module... well not new both were used on ebay but nothing has change.
the idle control valve does not even hum yet!! with any of the "new" parts on/.
im pretty much gonna give up cause my patience is running low... and i have no explanation to why its still not working. thats why im thinking its got to be something else in relation too idle or my temp gauge not working. ALL this going back to the shorts from jumping the wrong diagnostic pins!!! haha im having a breakdown about it.

oh well the car being not used has made me realize and appreciate the five series all over again. im debating whether to clean it up and service it or just part with it for 1500.00

so im taking it to my mechanic and just have him work it out on the idle and get a tune up while im at it. valves need to be adjusted. plus couple other things might as well do them now in conjuction with idle problem.

im dissapointed that i could not fully complete the repair. at this point it has only cost me 50 dollars on parts that may work or may not work!! I still dont truly know.

thanks again, ill be happy when its back on the road AGAIN!!
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#4 (permalink) Old 06-26-2008, 08:53 PM
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Lightbulb

>>>i figure i shorted the temp sending unit and now i need to replace the temp gauge sending unit. what input voltage does it hook up too???
<<< voltage to make the temperature circuit work is provided at the guage end. There is no need to input a voltage(if u do, your temp guage will blow and you do not want that)

the temp sender is what we call a THERMISTOR. It is designed to provide resistance when cold, and offer little or no resistance when hot.

The false or "lesser" readings u get on your guage almost always ponts to a faulty sender ;-)

>>>also on a different note... does the idle control module have an ignition supply control??
<<< idle control module gets it's voltage from the ECU/ECM(injection brain).

* Temp GUAGE alone has nothing to do with idle, believe me... it works on an independent circuit.

HERE's WHAT YOU CAN DO: (if u still havent lost patience)

Disconnect ALL the sensors on the thermostat head.
Disconnect your IDLE CONTROL VALVE(the cylindrical one)
Disconnect your Throttle Switch(that black thingie under your throttle body)

start the car. WITHOUT any electrics connected, your idle should be 750RPM (warm engine) In any case your idle IS NOT in the 750RPM range, your problem is mechanical & not electronic...

mechanical meaning... adjust the idle screw until you achieve 750 rpm & if you cannot achieve a stable 750... then start looking for vacuum leaks.

***so you are thinking of going back to the 5 series?... if you are looking pre-92 models.. you'll be surprised. engine and electrics are virtually the same ;-)
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#5 (permalink) Old 06-27-2008, 11:32 AM
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ya well i already own a 1990 525i its pretty much the same as the 85 325e just a couple differences some better some not so better haha

ok ill try disconnecting everything<<its probably the idle control valve if it still does not idle right
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#6 (permalink) Old 06-27-2008, 04:23 PM
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ok ill try disconnecting everything<<its probably the idle control valve if it still does not idle right

WRONG!.. u disconnect everything including idle control valve.

after you have disconnected everything.... and it still doesn't idle; move the stop screw inwards until u achieve 750 rpm.

if 750RPM is not attainable... then u probably have an intake leak or mechanical problem somewhere- and this needs to be corrected first before you can finetune the idle electrics
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