Testing cabin temp sensor fan motor

Post by **scot850** » 19 Oct 2017, 16:47

I planned to install the bag of spare cabin temp sensors to check they work. However, as they are a pain to access requiring removing the radio and ECC unit to get to it each time, I want to check the sensor fan actually runs before installing them as otherwise it is a waste of time. I suppose I could just try to connect each one with the connector without actually installing the ECC fully, but I thought I could shortlist them by say connecting a 9V cell across the live and ground terminals hoping it is enough power just to spin the fan.

Problem is the wiring diagram I have has the heating circuit but for some reason this does not include the temp sensor and it's 4 pin connector. Can anyone tell me which wires to the connector have which function so I can try to see if this would work?

I have also considered just check the fans work and just sell all the spares as a 2 for 1 as the chances of 2 being bad are low.

I'm also thinking if I wanted to be thorough, I could use a thermal temp sensor to check the temp output at one vent and at a set temp to see how accurate the temp sensors are relative to each others.

Thoughts and help on identifying the wire/pins is appreciated.

Neil.

Post by **BEJinFbk** » 19 Oct 2017, 23:51

Hey, Neil -
From what I see, you've got:

Motor Ground - Pin 2 - Black
Motor Power - Pin 4 - Yellow/Red

Thermistor - Pin 3 - Brown/White
Thermistor - Pin 5 - Yellow

Hope this Helps. Cheers!

Post by **scot850** » 20 Oct 2017, 08:04

Thanks my northern friend! That really helps! Now all I have to do is pull it all apart at least once to find the connector and which pins they go to on the unit. I couldn't have figured this out myself so thanks again!

Neil.

Post by **BEJinFbk** » 20 Oct 2017, 15:02

Always happy to help.

Is this something that you can use ... ?

: Screen Shot 2017-10-20 at 12.59.07 PM.png (22.12 KiB) Viewed 1899 times

Post by **scot850** » 20 Oct 2017, 18:48

I'll give it a whirl with a 9V battery and a couple of leads and see what happens. I'll report back. Weird how they list 5 pins but there are only 4 in the unit. Only electrickery people would do that to confuse us mere mortals!

Thanks again!

Neil.

Post by **BEJinFbk** » 20 Oct 2017, 19:04

We do what we can!
Possibly, they chose that to be sure that
it was different from nearby connectors.

Post by **scot850** » 21 Oct 2017, 17:43

So using the info supplied, I used a 9V battery and wired 2 leads to it and a couple of small screwdrivers clamped to the other ends. Touched the #4 pin with the +ve lead and #2 pin with the -ve lead and then watched for the motors spinning. I have 9 (yes 9!!) of these cabin temp sensors and all of them have been cleaned and lubed. All thankfully run nicely.

Also decided to do a resistance test. On my cheapo multitester, this can only be read in continuity mode. 6/9 gave a resistance of approx. 12.6 ohms +/- 0.05, and the other 3 strangely all read 12.9 +/- 0.5 ohms across the motor contacts.

So at least they all have good running fan motors. Does a resistance difference of 0.3 ohms make much difference?

Tried taking a resistance across the 2 pins for the thermocouple (pins #3 and #5) but go no response. Thought I might get a value like with the engine temp sensor, but nothing on any of them.

Neil.

Post by **jreed** » 22 Oct 2017, 06:39

I've got an 850 so the info may not apply to the V70, but the duct and cabin sensors on the 850 should generally measure in the 8-12kOhms range. I wrote up a easy way to test them all quickly here:
viewtopic.php?t=50443

Post by **abscate** » 22 Oct 2017, 08:45

scot850 wrote: ↑21 Oct 2017, 17:43 So using the info supplied, I used a 9V battery and wired 2 leads to it and a couple of small screwdrivers clamped to the other ends. Touched the #4 pin with the +ve lead and #2 pin with the -ve lead and then watched for the motors spinning. I have 9 (yes 9!!) of these cabin temp sensors and all of them have been cleaned and lubed. All thankfully run nicely.

Also decided to do a resistance test. On my cheapo multitester, this can only be read in continuity mode. 6/9 gave a resistance of approx. 12.6 ohms +/- 0.05, and the other 3 strangely all read 12.9 +/- 0.5 ohms across the motor contacts.

So at least they all have good running fan motors. Does a resistance difference of 0.3 ohms make much difference?

Tried taking a resistance across the 2 pins for the thermocouple (pins #3 and #5) but go no response. Thought I might get a value like with the engine temp sensor, but nothing on any of them.

Neil.

That resistance difference won't matter,and is probably less than the error in even a pretty good meter, no fluke intended.

Post by **scot850** » 22 Oct 2017, 09:09

Thanks guys (and yes the pun was received abscate!).

jreed, thanks for all the info. I need to spend some time reading it for the detail. I like the duct temp sensor info as I know I have some of those kicking around too somewhere!

What I found strange was I was getting no resistance reading on the temp sensor pins which I was hoping to use to see if they are all reading in the same range for temperature. Then that would mean I would be able to carry out 'field' test at PnP when pulling parts for all the sensors. It is a 50km round trip to the 2 x PnP from my house so a pain/expensive to return parts that are only found to be faulty later. I could even test the parts in the car after buying and return them right away if needed.

When testing the cabin temp sensors (I am no electrical genius) on the resistance settings all I got was a 1. on all settings.

Many thanks,

Neil.