Tyler T5R Posted May 5, 2011 Report Share Posted May 5, 2011 98 V70r. On startup, sometimes coolant temp gauge shoots up and down in ways that indicate physically impossible temperature changes. At same time, orange lights on climate control flash for about 30 seconds. Needle eventually settles down at normal spot after a couple minutes. Most other tkmes needle and ACC work fine Where do I start 'diagnostics' instead of my usual 'random parts replacement'? Link to comment Share on other sites More sharing options...
--Aaron-- Posted May 6, 2011 Report Share Posted May 6, 2011 do you have a CEL? this sounds like your ECT sensor.the CC lights are telling you theres a fault, try gently spraying air into the opening which is in between the right portion of dash switches and the CCmost of the time the lights point to the blower motor and or resistor but can be a number of damper motors among other things Link to comment Share on other sites More sharing options...
Gilhuly Posted May 6, 2011 Report Share Posted May 6, 2011 You can clean the connector for the coolant temp sensor first and see if it makes a difference. You likely just need a new one and they aren't very expensive. Link to comment Share on other sites More sharing options...
jablackburn Posted May 6, 2011 Report Share Posted May 6, 2011 The climate control is probably also mad at the ECT sensor - it uses it to determine water temp. for heat too. I'm surprised if your car is doing that it hasn't thrown a CEL light yet. Link to comment Share on other sites More sharing options...
--Aaron-- Posted May 6, 2011 Report Share Posted May 6, 2011 great info blackburn, didnt know that Link to comment Share on other sites More sharing options...
Tyler T5R Posted May 6, 2011 Author Report Share Posted May 6, 2011 Never had a CEL on this car. Will try the suggestions this weekend. Thanks Link to comment Share on other sites More sharing options...
Oreo931 Posted May 6, 2011 Report Share Posted May 6, 2011 The climate control is probably also mad at the ECT sensor - it uses it to determine water temp. for heat too. I'm surprised if your car is doing that it hasn't thrown a CEL light yet. I've never had a CEL for a bad ECT. I've replaced it on 3 cars due to fluctuating temp gauge as well. Link to comment Share on other sites More sharing options...
db130 Posted May 6, 2011 Report Share Posted May 6, 2011 i'd change the ECT fairly soon - if the needle is dancing, that means it's also reporting erratic readings to the ECU and in extreme cases it will cause the car to not start if the ECT dies completely. now the obligatory VS suggestion when changing the ECT: "it would be a good time to replace the thermostat & thermostat gasket as well" Link to comment Share on other sites More sharing options...
Bah Posted May 6, 2011 Report Share Posted May 6, 2011 http://volvospeed.com/volvo_repairs_how_tos/engine_repairs/ect_sensor_coolant_replacement.html - Just in case :lol: Link to comment Share on other sites More sharing options...
Oldariel Posted May 6, 2011 Report Share Posted May 6, 2011 My 1993 850 GLT had the same symptomes a while ago. First the needle began to jump up and dowon and the lights on the AC began to blink, after a day or two the Lambda light (I think it's the same as CEL) came on and the blower motor stopped working altoghether. There were some stored codes that helped me indentify the engine temp sensor as the culprit, but I don't remeber exactly which ones. During the repair I found all the following things were shot: - engine (coolant) temp sensor - air blower motor power stage (resistor?) - engine ECU (after replacing both above items and reseting the codes, the CEL came back almost immediately and one of the codes reappered. I cleared it twice or three times, but until I replaced the ECU for a known good unit, the CEL and code alwayas came back) When replacing the engine temp sensor I found the insulation on the wires was striped where they rubbed on one of the metal parts around there. I'm not sure if that can be the reason for the engine ECU failure, or how it was all connected to the blower motor power stage failure. It could have just been a coincidence. But if it wasn't a coincidence I could have avoided the ECU failure if I replaced the sensor immediately. So just out of caution, try to check your temp sensor out as soon as possible. Link to comment Share on other sites More sharing options...
Guest JTSPO Posted May 11, 2011 Report Share Posted May 11, 2011 I've never had a CEL for a bad ECT. I've replaced it on 3 cars due to fluctuating temp gauge as well. It could but not always. It throws a code when the engine runs rough because the wrong ratio. But it is possible no code was caused. Keep the bad ECT and it will give you a code in the long run. Link to comment Share on other sites More sharing options...
Dick Dastardly Posted May 12, 2011 Report Share Posted May 12, 2011 I've never had a CEL for a bad ECT. I've replaced it on 3 cars due to fluctuating temp gauge as well. Mine didn't trip a CEL last time either...just a gauge that didn't move accordingly and crappy hot-start Link to comment Share on other sites More sharing options...
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