[2001 V70 2.4T] Coolant Wars: The Coolant Strikes Back

[prwood]

I replaced the Volvo connectors with a pair of crimped disconnect terminals, with some dielectric grease, wrapped in some electrical tape. I have driven it a few times since then, and the results are a bit mixed.

First, here's a graph of speed, rpm, and ECT from my first trip out. The ECT seems to be more stable than I had experienced before repairing the signal wire.

IMG_2061.PNG (467.4 KiB) Viewed 911 times

However, on a later trip out, I got this result:

IMG_2069.PNG (346.86 KiB) Viewed 911 times

The ECT kept climbing while I was idling and it didn't come on when I would have expected around 225-230F. It actually got up as high as 248F, at which point I turned on the heater and vented the heat inside. You can see it came down pretty well after that. I shut the heater off when the temp got down under 200F. But the ECT it didn't settle into a more regular cycle, and then started climbing back up.

So I'm still not sure that the fan is coming on every time when it should, despite having rewired the fan signal connector. Is it possible that the fan, fan controller, or fan relay is failing? What would be the diagnostic approach for figuring that out?

[jonesg]

pop the hood and look to see if the fan is coming on.
read the voltage on the signal wire at the new connector and/or at the plug going into the distribution box.
I suspect you're losing the signal.

vida will tell you if the signal is missing.
if you get 2 to 5v on the signal wire but no fan at high temp then maybe its the relay which can be changed or pulled at hollands salvage.

[prwood]

The fan definitely *does* come on most of the time at expected temperature of 225-229F, and shuts itself off at 210F - I have witnessed it. But it also occasionally seems to *not* come on when the temps are in the higher range (230-240F), typically in situations where I can't get out of the car to look at it. This is my assumption anyway, based on the fact that the temperature does not start cooling down when I expect it to, having not been able to observe the fan directly in these cases.

For reading at the signal wire connector, would I just disconnect it and check for the voltage on the end coming from the wire harness? And then wait for the ECT to reach a temp where the fan should kick in and verify the voltage?

When you mention testing at the distribution box are you talking about the ECU or the fuse box?

Regarding the relay, I'm a bit confused at what I'm seeing online - some people mention the relay being built into the fan control module (and thus can only be replaced as part of a replacement of the fan control module), other people say it's on the underside of the fuse box, not sure if those are two different things.

[jonesg]

distribution box, located behind airbox, contains fuses and relays, the signal wire passes through on its journey to the fan.

I'll check for voltage on my signal wire, its 3 am right now.

your experiences with no fan at high temps are not verified. The high temp reading might be wrong, I'd verify with infra red gun on the thermostat housing. Sometimes its just worry. Especially suspect numbers if you get a reading near 250 but the temp gauge on the dash is still in the normal range. Something doesn't add up.

[dikidera]

distribution box, located behind airbox, contains fuses and relays, the signal wire passes through on its journey to the fan.

I'll check for voltage on my signal wire, its 3 am right now.

your experiences with no fan at high temps are not verified. The high temp reading might be wrong, I'd verify with infra red gun on the thermostat housing. Sometimes its just worry. Especially suspect numbers if you get a reading near 250 but the temp gauge on the dash is still in the normal range. Something doesn't add up.

Not my personal observation, but I have been told that the temp gauge is strongly vertical up to at least 128c his 250f is only 121c. This is intentional by Volvo.

[jonesg]

when my fan was dead I watched the gauge climb at idle into the hot zone, as soon as I started moving it dropped down again.
i presume if the needle is still vertical its still ok to run.

[jonesg]

cold engine, at idle, AC off, I get approx 8v at the dist box by back probing the purple wire with a pin.
but nothing at the fan plug.

At idle with AC on, fan turning , i get 1.5 - 2v at the fan plug, you can briefly pull the plug to read v it will not affect the ac or engine...the fan will stop but the command v is still there.

purple wire obviously passes through some switching relay or circuit at the dist box.

[prwood]

distribution box, located behind airbox, contains fuses and relays, the signal wire passes through on its journey to the fan.

I'll check for voltage on my signal wire, its 3 am right now.

your experiences with no fan at high temps are not verified. The high temp reading might be wrong, I'd verify with infra red gun on the thermostat housing. Sometimes its just worry. Especially suspect numbers if you get a reading near 250 but the temp gauge on the dash is still in the normal range. Something doesn't add up.

Not my personal observation, but I have been told that the temp gauge is strongly vertical up to at least 128c his 250f is only 121c. This is intentional by Volvo.

When the temperature got up to 248F, the temperature gauge actually moved one full tick mark past vertical, which is the most I have ever seen it move past vertical.