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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #1
hi guys,

my temperature gauge does not come up while driving long distance.
i replaced the sensor, thermostat and sender for newones, but now the gauge is going almost directly to the hot zone.
i bleeded the system by running the engine for long time without the radiatorcab and after a 30 minutes it was not bubbling anymore.
does anyone knows the or a solution?

thanks, paul
 

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Is the car actually overheating or is it just the gauge that is malfunctioning?
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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156 Posts
Discussion Starter #3
Hi NAJ,

it is just the gauge that is malfunction.
first to low, later to high
 

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1)The gauges are not that accurate and the gauge reading may/will change depending on ambient temperature even though the coolant temp is actually correct.
2)Verify actual coolant temp by backprobing the CTS and reading the voltage, you can also do this while driving (with a helper of course)
Backprobing the CTS.JPG CTS VOLTAGE CHART 2.jpg

3)Be sure you have the correct sending unit.
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #5
okay, i messured 158 F temp and 104,6 v
can you do something with these info?
 

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158 degrees F on a fully warm engine??? Way too low, with temps that low on a fully warm engine it appears you have a stuck open thermostat.(New does not always = good)

You should be using a 192/195 degree thermostat.
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #7
okay, sounds good. although i bought 2 new ones.
Can i remove the thermostat and drive the car?

whenn i disconnect the connector from the sender, the fan immidiatly starts spinning around.
so i guess you are right with this. i will buy another one tommorow.
hope this will be helpfull so i can start old issue again. The speed control.
i am expecting a fully refurbished bcm one of these days. Could that be helpfull for SC issue?
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #8
i also put the old one back in the car with the same result, very high temperature.

when replacing the temp sensor and re-connect the little cap, the wire broke, so it has a malfuntion before, i assume.
i repaired it, but start thinking now, does the wire need a required resistance or can i solder an little thicker wire?
 

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If the fan runs when you disconnect thehe connector you are disconnecting the Coolant Temperature Sensor not the Temperature Sending Unit which controls gauge function.
The sending unit is a single wire.
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #10
o dear, then i was wrong with information.
what to do next by then. replace the new TSU for the old one again or still the thermostat?
by the way, do you work on sunday?
 

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If the gauge is not functioning correctly you first want to verify actual coolant temp is correct, to do that backprobe the Coolant Temp Sensor(2 wire) and read the voltage for which I sent you the voltage to temp chart.
At idle you should reach the proper voltage/ temp for the cooling fan to cycle on and off as the temp lowers.
If coolant temp is low or high then you have to determine what is causing that issue.

After you have verified coolant temp is correct then you can diagnose gauge reading incorrectly issues.
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #12
i think i don't understand backprope.
that means i messure the voltage on the 2 wires? So, put red in a wire and the black and messure with the multimeter on Volt dc?
 

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Backprobing means you are going to probe/check voltage on a connector while the connector is still connected so you can read live data.
You do this by using probes that will be placed into the connector from the backside that will make contact with the terminals in the connector, you then connector your + and - leads from your voltmeter to those two probes to read the voltage.
Backprobing the Coolant Temp Sensor connector with the two voltmeter leads allows you to read actual Sensor Voltage and watch the voltage change as temp increases.
BACKPROBING THE COOLANT TEMPERATURE SENSOR (CTS) CONNECTOR
Backprobing the CTS.JPG




Both the Coolant Temperature SENSOR and the Coolant Temperature SENDING UNIT are located next to the thermostat housing on the 3.0L engine.
The Sensor is a Two Wire Connector, The Sending Unit is a Single Wire Connector.

COOLANT TEMPERATURE SENSOR
(Used by the engine controller to know actual engine temperature for spark advance, injector pulse, idle speed and cooling fan control)
(The Sensor has nothing to do with gauge function)

COOLANT TEMPERATURE SENDING UNIT
(A Variable Resistor that controls coolant temp gauge function only, the sending unit plays no part in the electronic engine controls of the engine)
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #14
welli i restored everything to the old situation.
now the temperature gauge is staying low on the dash.
i drove a while and the engine is warm, like the car inside,. Heater is working fine and fast
i messured temp and voltage from TSU, 162 F by 108.4 V
CTS 126 F by 90 V
valvecover 121 F
airhouse 74.5 F
 

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You have your voltmeter on the wrong scale, you are set on millivolts (mV) rather than volts (V), converting your readings does not make any sense.
Converting your 133.4 mV to Volts = .1334 Volts.
Your Coolant Temp Sensor Readings should be in the 4 volt + range on a cold engine before it is even started and drop down as the engine temp increases, at 217 F the voltage should read 2.05 volts and the cooling fan should cycle on.
Also you need to use a backprobe pin of some sort to backprobe the connector, the leads of the DVOM are too large and will/may damage the connector or touch each other giving false readings.
You can use paper clips if needed.
Also and it does not affect the reading, your leads are backwards, when you see a - in front of the number you have the polarity wrong, just switch the leads.

Backprobing the CTS.JPG
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #17
okay, i trie again tommorow. it is dark now.
i'm still learning, sensei!
but is temperature engine okay? the radiatorcab is not even warm after driving 20 minutes.
 

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I had to look, you are 6 hours ahead of us, it is Noon where I am at on the East Coast.
Have a Good Night!!!
 

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Chrysler leBaron 1990, 3.0 V6 convertible
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Discussion Starter #19
yess, we are real close to each other.
i wish you a good night too, Jan!
 
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