Coolant Light On After Moving Bottle

jamesbeat · Post by **jamesbeat** » 01 Aug 2016, 06:15

I am going to replace my timing belt soon, so yesterday I had a poke around in that general area to confirm that I have the right parts and tools.

One of the things I did was lift the coolant reservoir out of the way as shown in the tutorials.
I didn't unhook anything except the sensor wire, and I am confident that I reconnected it correctly.

This morning when I started the car (for the first time after reassembling everything) the coolant light came on.

I had a look at the bottle, and everything seems to be in order. The connection.for the sensor is definitely hooked up right, I didn't damage any hoses, and the coolant level is still a maximum.

I thought it was probably an air bubble from inverting the bottle, so I jiggled it around a bit and the light went out.

However, I was halfway to work and it came back on again.

I have checked, and everything looks fine. The coolant level is still at maximum, wires are still hooked up, no leaking.

I feel like inverting the bottle has caused an air bubble to get trapped or something, but I can't figure out exactly what happened or how to remedy it.

Any ideas?

Post by **theWIFES_S70** » 01 Aug 2016, 08:56

james,
You probably have a coolant level sensor (https://www.fcpeuro.com/products/volvo- ... -uro-parts that is on the outs. (Guys, I have no idea why the link has the words URO in it, this is for the OEM version!)

It's a relatively cheap replacement. But before doing that, you could try disconnecting the connectors and cleaning them with something sensitive like MAF cleaner, letting it dry and then reconnecting. I've had a lot of luck doing this with fouled up connectors. I noticed that the connectors were really dirty when I did my timing belt job. It's a pretty essential sensor to have working on your car so make sure you take action!

Post by **abscate** » 01 Aug 2016, 09:25

You only have about 4-5 inches of play when you lift the coolant reservoir, or else you will damage the connections on the sender.

I learned this the hard way.

It was Abby's first repair on her Volvo.

Pics here

https://www.matthewsvolvosite.com/forums ... by#p292541

jamesbeat · Post by **jamesbeat** » 01 Aug 2016, 10:06

Hmm. There definitely was some tugging on the wires - my friend was holding the tank out of the way while I was figuring out how to disconnect the cable, and I did wince at one point when he moved it a little too far and pulled quite hard on the wires.

I'll have to take a look at it later and see what got damaged.

Edited to add:
Is there an electrical test I can perform on the sensor to find out what's wrong with it?
Does the light come on when the circuit is open or when it is closed (or when resistance is high or low)?

101 · Post by **101** » 01 Aug 2016, 11:25

For $25, I wouldn't mess with it. Just replace it with a new Volvo sensor.

That coolant level sensor is your first line of defense to prevent coolant loss and engine overheating when:
- the heater core decides to takes a dump
- the plastic neck on the radiator decides to break off
- one of the turbo coolant hoses decides its had enough oil leaking on it

(yes - I've experienced all three).

Post by **abscate** » 01 Aug 2016, 11:36

Its connecting pin A15 on the CDM to pin 31/50 connector, only 1999 ME7 - I think your 2000 is the same

I know thats useful to someone, but not me.

(Im still current tracing it)

OK - think I have it. Its a bit strange.

X terminal (12VDC from ignition switch) feeds 12V to terminal 31/50. When the coolant sensor closes it feeds 12V to pin A14 on the CDM which I believe keep the low cooling light OFF

If you run low on coolant, or disconnect the sensor, 12V drops off and the coolant level light is turned on.

This needs to be confirmed, but the cooling level switch is shown as normally open - this is how a good engineer would design this, by the way.

jamesbeat · Post by **jamesbeat** » 01 Aug 2016, 13:56

Yes, it's definitely a wise choice to have the sensor fail safe - a false check engine light is better than it not coming on when needed
I bet I pulled on a wire too hard and it's not making contact properly and throwing a cel.

I agree that since its a safety issue, replacement is the right course of action.

Thanks guys

jamesbeat · Post by **jamesbeat** » 01 Aug 2016, 16:26

The plot thickens...

I just disconnected the sensor and tested it.
I get an open circuit across the terminals, and when I put a magnet near it, the circuit closes.

The same thing happens when I connect it to the car - when the sensor is connected, the light comes on. When I put it near a magnet, the light goes out.

This leads me to believe that the sensor is ok, but the floating magnet in the tank is not floating properly

Is this a thing? Could this have happened when I inverted the bottle?

I can't open it to check it yet because the car is hot and I'd rather not cook my hand.

Post by **Ozark Lee** » 01 Aug 2016, 16:39

Smack the tank and see if things get better. I have had the float stick a couple of times but one good pop with the palm of your hand can often free the float. If it stays stuck about the only solution is to replace the tank.

...Lee

jamesbeat · Post by **jamesbeat** » 01 Aug 2016, 17:41

I let the car cool down and opened the bottle.
I used a screwdriver to push the float down, and it appears to be working fine - it moves freely and pops right up as soon as I take the screwdriver away.

The light stays off since I pulled out the sensor and replaced it, although I haven't driven it far yet

I did clean the connections with MAF cleaner, so some combination of what I did seems to have worked, at least for now.

If I get any more problems, I'm going to suspect the car side of the wiring, as the sensor appears to be in good shape.

It's possible that I just dislodged the sensor the first time around, and removing and replacing it fixed that.

We'll see I guess...