Inacurrate temp display on a 90

JeffP1167

JeffP1167

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Dec 21, 2009
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Yucaipa, CA.
After a few hours of work trying to replace the temp sensor on my 1990 ... well I think it is the correct sensor (mounted in the radiator shroud) I am still showing temps that are way off. It does however seem to change displayed temps which it has always done anyways. Could the controller or the head unit be the real cause of this? I tried the code retrieval process and none are displayed the system seems to also operate normally meaning all selector buttons make the system work differently.

I am unsure of the true outside temperature but what this thing shows is off a considerable amount.

Any of you had issues like this with a 90?
 
Twin_Turbo said:
Could be a wiring issue (resistance)
Click to expand...

are these outside temps critical to how the system operates? Also was this type of thing accurate in the first place?

I did try another head unit and it did the same thing. Any ideas what wires to trace and test? two wires go to this sensor so how much resistance should be there for certain temps?
 
by considerable differences I mean yesterday at night was about 70-75 degrees yet displayed temps were about 28 degrees. I have checked for wires rubbing metal but none have been found by the sensor. The rest is buried in a harness and impossible to inspect that.

I'm going to try another sensor and see maybe if I just got a bad one is all.
 
I believe the air and water temp senders are electrically identical.....

I can't imagine the outside air temp sender would be different....plug one of them in with clip leads...give it a shot, anyway....

:drink:
 
mrvette said:
I believe the air and water temp senders are electrically identical.....

I can't imagine the outside air temp sender would be different....plug one of them in with clip leads...give it a shot, anyway....

:drink:
Click to expand...

I think you might be confused as to what temp I am referring too. This isn't a coolant temperature issue. This has to do with the C68 climate control digital temperature readout. This has to be the sensor that controls the readout of that temperature display. Looks like air hits a sort of resistor inside of it and that changes the resistance. I have no idea of the true temps outside or whether this system when stationary can give a accurate reading as well. However at any given time when parked (never tested driving) it is probably a good 40 degrees off. I have seen the temp display at 99 degrees though so I know it can detect hot temps outside.

one other thing that is not yet hooked up is a sensor at the base of the windshield inside of the car. Not sure what this sensor does or if it is related to the C68 or whether it can cause this temp difference.

tempsensor.jpg


you can see in this picture 99 degrees was displayed and later that evening the system took a dump.

dash1-1.jpg
 
service ABS? WD40 the crap out of the lateral accelerometer and connector (the box under the radio), it fixed my light issue. If that doesn't work, jumper aldl a & h and read codes

you can diagnose codes from the HVAC controls by holding blower speed up & down until it displays -00

up and down arrows then displays the parameter number and then pressing the fan "auto" button will display the value

[tr] [td] Parameter Number[/td] [td] Parameter Description[/td] [td] Valid Values[/td] [/tr] [tr] [td] 0[/td] [td] System Faults (one of these will be set if your air conditioning controls have an LED flashing)[/td] [td] 00=No Faults 01= Temp Door Motor Circuit Fault 02= Temp Door Motor Circuit Fault 03 = Ambient Sensor Open 04 = Ambient Sensor Short 05 = In-Vehicle Temp Sensor Open 06 = In-Vehicle Temp Sensor Short 07 = Solar Load Sensor Open 08 = Solar Load Sensor Short 09 = Low Freon Detected 10 = UART Failure[/td] [/tr] [tr] [td] 1[/td] [td] Temp Setting[/td] [td] 60F to 90F[/td] [/tr] [tr] [td] 2[/td] [td] In-Car Temp Sensor[/td] [td] 10 = HOT -130 = 230 = COLD[/td] [/tr] [tr] [td] 3[/td] [td] Outside Temp Sensor[/td] [td] 10 = HOT -130 = 230 = COLD[/td] [/tr] [tr] [td] 4[/td] [td] Sun Load Sensor[/td] [td] Max light Max Dark L98 38 183 LT5 115 -110 = 210 <i> [Notice the solar shield effect!]</i>[/td] [/tr] [tr] [td] 5[/td] [td] Ignition System Voltage[/td] [td] 0 = 9 Volts -155 = 255 = 16 V[/td] [/tr] [tr] [td] 6[/td] [td] Engine Speed (RPM divided by 25)[/td] [td]-----[/td] [/tr] [tr] [td] 7[/td] [td] Vehicle Speed[/td] [td]-----[/td] [/tr] [tr] [td] 9[/td] [td] A/C System Mode[/td] [td] 00 = OFF 01 = Re-Circulation 02 = A/C 03 = Bi-Level 04 = Heater 06 = Defrost 07 = Vent 10 = Manual Re-Circulation[/td] [/tr] [tr] [td] 10[/td] [td] Blower PWM[/td] [td] 0 = 0 Volts 128 = 14 Volts[/td] [/tr] [tr] [td] 11[/td] [td] Program Number[/td] [td] 00 = COLD -155 = 255 = HOT[/td] [/tr] [tr] [td] 12[/td] [td] Mix Number[/td] [td] -155 = 255 = COLD 00 = COLD[/td] [/tr] [tr] [td] 16[/td] [td] Coolant Temperature In degrees C[/td] [td]-----[/td] [/tr] [tr] [td] 17[/td] [td] Solar Correction[/td] [td] 114 = Max light 128 = max dark[/td] [/tr] [tr] [td] 30[/td] [td] Stored Full Hot Value[/td] [td] 0 to 50[/td] [/tr] [tr] [td] 31[/td] [td] Temp Door Travel Range[/td] [td] 100 to 200[/td] [/tr] [tr] [td] 34[/td] [td] Temp Door Position Requested[/td] [td] 00 = Full HOT -153 = 253 = Full COLD[/td] [/tr] [tr] [td] 35[/td] [td] Compressor On Time[/td] [td] .1 second increments[/td] [/tr] [tr] [td] 36[/td] [td] Number Of Times Below Critical Time[/td] [td]-----[/td] [/tr] [tr] [td] 37[/td] [td] Software Version Number[/td] [td]-----[/td] [/tr]
 
that accelermeter is just laying off to the side of the trans tunnel right now. Is that what triggered the abs service?
 
JeffP1167 said:
that accelermeter is just laying off to the side of the trans tunnel right now. Is that what triggered the abs service?
Click to expand...

hell yea, it's a g meter. if it's on it's side it will see a constant g load of 0.98 (that's gravity at work there)

It works like this, if you're traveling fast and go around a sharp corner the inner wheel will turn much slower than the outer and the difference in speed and the vehicle speed would trigger the abs when you tap the brake in the corner resulting in loss of control, the g meter tells the abs control module the g load and it'll not work the rear circuit.

Now with you having the accelerometer off to the side and not level and centered in the car it'll detect a g load, not a problem but nobody makes an indefinite lasting turn so it's programmed to trigger a fault code when the g load lasts more than 120 seconds
 
BBShark said:
JeffP1167 said:
Twin_Turbo said:
JeffP1167 said:
about 70-75 degrees yet displayed temps were about 28 degrees.
Click to expand...

dude, 80F is about 28C, are you sure it's not set to metric?
Click to expand...

what do you mean set to metric? I've never changed anything on the car.
Click to expand...

See the button Eng/Met at the upper right of the trip monitor panel?
Click to expand...

Yes but the car defaults to english when started but the temp reading doesn't. So I don't think that is what is causing it.
 
default is only english after removing battery power, otherwise it will be set to whatever it was set at when the ing. was on for the last time.
 
Twin_Turbo said:
bad operator :)
Click to expand...

I just never payed attention to what it did before and had a short somewhere so always disconnected battery. this was first time Ive seen it do this and its not like it says 80f or 28c

also never had a car with all this electronic stuff.

mis-informed operator!
 
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