IPD sale XeMODeX - Experts in Volvo Electronics
Did you know? 🤔
Logged in users can get email notification of topic replies Log in or register (free).
Amazon Link Buy your stuff using this and it helps MVS!

850 Turbo Coolant Temp Sens, or Sensor Connector ?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Nick777
Posts: 13
Joined: Thu Oct 24, 2019 7:40 pm
Year and Model: 1995 850
Location: New Jersey
Has thanked: 0
Been thanked: 1 time
United States of America
Nick777

850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by Nick777 » Sat Nov 16, 2019 1:25 am

Ok, so heres the symptoms and my reasoning:

My Temp gauge has been acting crazy shortly after I purchased the car. The needle would at times seem to act normally, rising normally to just a hair beyond mid-line, only to plummet to Zero, then rise back to approx mid-line, then plummet, repeat and repeat (I know its not a malfunctioning cluster gauge because I could hear and feel the engine adjusting when the Temp needle would plummet). So clearly something is off - but is it the sensor or the connector?

But yesterday the sensor did something Very interesting. Upon starting an absolutely cold engine, the Temp shot right up to mid-line, right away. Now given that these sensors are Negative Temp Coefficient sensors (the Resistance goes Down as they heat up), the fact that the needle shot up right away tells me that it can't possibly be the sensor connection. Reason why - any kind of connector issue would cause an Increase in resistance (corrosion, crud, partial open), yet the sensor is acting right off the bat as though there's a resistance Drop. This, along with the fact that there is NO evidence that the gauge in the cluster is malfunctioning tells me that it is HIGHLY likely to be the sensor itself.

Furthermore, although I will change the thermostat because I don't know how old it is, it would be physically impossible for even a trashed thermostat to cause a reading of instant heat on a cold engine.

So it MUST be the sensor!

What do you guys think?



User avatar
abscate
MVS Moderator
Posts: 19174
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 229 times
Been thanked: 759 times
Trinidad & Tobago
abscate

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by abscate » Sat Nov 16, 2019 3:06 am

Pull off the connector and check the pins for corrosion. Then pull the part number,search forum here for that part number and the resistance table, and confirm it Errors of about 10% are ok

The new part is about $50

Pick and pull less

I think I have one of my 1998 parts car , too. If you are tapped out and fighting the man, it’s free, otherwise market value or something in between.


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

User avatar
RickHaleParker
Posts: 3210
Joined: Mon May 25, 2015 2:30 pm
Year and Model: See Signature below.
Location: Kansas
Has thanked: 3 times
Been thanked: 374 times
United States of America
RickHaleParker

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by RickHaleParker » Sat Nov 16, 2019 3:42 am

Nick777 wrote:
Sat Nov 16, 2019 1:25 am
So it MUST be the sensor!
Intermittent electrical shorts will lower the resistance. Conductive corrosion in parallel with the temperature sensor will lower the resistance.


Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

Nick777
Posts: 13
Joined: Thu Oct 24, 2019 7:40 pm
Year and Model: 1995 850
Location: New Jersey
Has thanked: 0
Been thanked: 1 time
United States of America
Nick777

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by Nick777 » Sat Nov 16, 2019 10:26 am

Abscate - thanks for the info and especially for the offer! I'm not quite in financial dire straits (yet!) so I'll save your offer for if and when I really need it!

RickHaleParker - very interesting! I wasn't considering that there could be conductive corrosion, even though I'd imagine that resistive corrosion is far more likely. As to intermittent shorts, also another good observation. As a matter of fact i wonder if that is in fact going on in my situation - on one occasion I observed the temp needle shoot all the way to the tippy top even though the engine was clearly not overheating (just started more or less). An intermittent short would plummet the resistance to near zero, which would explain the needle jumping to the top like that!



User avatar
RickHaleParker
Posts: 3210
Joined: Mon May 25, 2015 2:30 pm
Year and Model: See Signature below.
Location: Kansas
Has thanked: 3 times
Been thanked: 374 times
United States of America
RickHaleParker

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by RickHaleParker » Sat Nov 16, 2019 5:09 pm

Nick777 wrote:
Sat Nov 16, 2019 10:26 am

RickHaleParker - very interesting! I wasn't considering that there could be conductive corrosion, even though I'd imagine that resistive corrosion is far more likely.
Resistance also has conductance. Resistance is some where between a perfect insulator and a perfect conductor.

Resistance and Conductance are reciprocals of each other, like Yin and Yang there is some of the other in each.


Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

User avatar
abscate
MVS Moderator
Posts: 19174
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 229 times
Been thanked: 759 times
Trinidad & Tobago
abscate

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by abscate » Sat Nov 16, 2019 5:17 pm

Isnt resistance more Buddhist, like Ooooohhhhhmmmmmmm?


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

User avatar
wizechatmgr
Posts: 1280
Joined: Thu Jan 12, 2017 1:07 pm
Year and Model: 1999 V70 XC AWD 2.4T
Location: Albany, NY area
Has thanked: 22 times
Been thanked: 53 times
Contact:
United States of America
wizechatmgr

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by wizechatmgr » Sat Nov 16, 2019 5:21 pm

abscate wrote:
Sat Nov 16, 2019 5:17 pm
Isnt resistance more Buddhist, like Ooooohhhhhmmmmmmm?
You're baaaadddddddddd =P


Wisdom requires knowledge as a prerequisite, but knowledge can be developed due to a lack of wisdom.
In order to learn how to fix something, you must first learn how to break it.
1999 V70 XC AWD - ~183k miles

User avatar
erikv11
Posts: 9365
Joined: Sat Jul 25, 2009 2:03 pm
Year and Model: 850, S/V70, 06 S60R
Location: Iowa
Has thanked: 72 times
Been thanked: 227 times
United States of America
erikv11

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by erikv11 » Sun Nov 17, 2019 7:56 am

If you need to buy another ECT, this is another part for which the cheap aftermarket ones often don't work.


'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 140k
'98 S70 NA, 210k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 280k
'06 S60 R, 160k
gone: '96 NA 850 210k, '98 NA V70 182k

User avatar
abscate
MVS Moderator
Posts: 19174
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 229 times
Been thanked: 759 times
Trinidad & Tobago
abscate

Re: 850 Turbo Coolant Temp Sens, or Sensor Connector ?

Post by abscate » Sun Nov 17, 2019 9:19 am

Driving through NJ all week MON TUES. WED

Give me a PM and see if we can connect


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

Post Reply
  • Similar Topics
    Replies
    Views
    Last post