Cooling Fan Coming on Late, I Think? Topic is solved

[WhatAmIDoing]

What coolant-to-water ratio have you (or a shop) measured?

No idea. Never been measured.

If the low speed connector comes off its pin on fan relay then the high speed fan will be triggered at a higher temp. The plastic on those "bullet" style connectors disintegrates and the grey plastic connector body can't keep them on. Easy to inspect. Look just under that top fan shroud plastic bar for the big rectangular relay and see if the grey plastic two wire connector has a loose wire. If it is loose then push it back up on the pin on relay.

I inspected the fan relay. All the connectors looked good. Jiggled and pushed them all in to make sure they were fully seated.


Okay, now it's data time. Figured out how to make my OBDII scanner read live data. First I started the car and let it warm up a bit. Ambient temp 83F. ECT read 90F at startup. Turned on the A/C to see if that would make the fan come on. Fan came on when the needle hit 4 o'clock (sorry, but wasn't looking at the scanner). A/C was blowing very cold on max cool. Drove ~1 mile on a dirt road, second gear, ~20mph. Temp hovered around 190F with peaks at 193. Turned on a main road, put the hammer down, temp shot to 204 before I let off going into 3rd. Drove a few miles always in 3rd gear between 2000 and 3000rpm. Temp stayed between 190 and 202. Stopped for a hard left back onto the dirt road, and temp shot to 207 very briefly before I started moving again. Went 1 mile on a hilly dirt road, 2nd gear, ~20mph. Temp started at 194, climbed slowly as I was travelling uphill and peaked at 215F at the crest of the hill (needle one notch above 3 o'clock), then just before I let off the temp began dropping. Downhill it was at 190-193 and stayed there the rest of the way. Parked the car, turned off the A/C, turned off the blower. Temp slowly began climbing from 193F while it idled. At 205 the fan did not come on. After a few minutes, it hit 215F and the fan finally came on. Temp peaked at 217 (needle about where pictured above). Temp steadily dropped to 199F and fan shut off, needle back at 3 o'clock, I turned off the engine, and turned the key back to 'run' position. Watched the temp go back up to 204 with spikes up to 208F. *All temps are in degrees Fahrenheit converted from Celsius by the scanner.

Based on what I've read, the fan should come on with the engine off over 205F? The fan spun with ease, key still in position 2 (yes I realize this isn't a smart idea). I could hear an electrical buzzing noise with the key still on pos 2. It was coming from near the fan motor area, picture attached.

Assuming The ECT is reading the correct temperature, and that the scanner is translating the temperature correctly, and since the temps are within normal operating range while the vehicle is moving at normal road speeds, It would appear that the issue lies with inadequate airflow passing through the radiator. I'm guessing for some reason the low speed fan is not coming on. So once again it looks like I'll be chasing an electrical issue.

[WhatAmIDoing]

Going off a post on volvoforums about diagnosing the cooling fan when it doesn't come on, I pulled the the middle, gray plug on the fan relay controller. I then jumped one pin at a time to ground for about 2 seconds. I managed to get both the high speed and low speed fan to actuate. So at least now I know where the problem lies. The fan isn't being told to come on when the ECT reads over 205F, but the high speed comes on when the temp hits 215F. The fan also comes on when the A/C is turned on like it's suppose to.

So does this mean the relay is bad ($75), or bad wiring, or both? Or could there be another problem. I doubt the ECM is bad. Does anyone have a wiring diagram for the cooling system? And how would I test if the relay is bad (really don't want to buy a new one)?

If my temps are hitting 215F, is the car still okay to drive for the meantime? I think there still a pretty good gap before I have to worry about overheating and the coolant boiling .

[jimmy57]

If you have an old fashioned bulb test light you can test for the signal from ECM. If you connect the alligator clip to batt pos and then probe the low speed trigger wire, yellow/white one, then the light should light to indicate the ECM grounding for low speed at 205-210. The signal won't show readily on a DVOM unless it has the voltage present to see the contrast of voltage and then 0.7-1.1 V DC when the ECM outputs ground. The connectors used on that relay for the ECM signals aren't backprobe friendly to check it with the two wire plug connected.
If you ground the two pins and get the two speeds it is leaning to no signal from ECM or problems with the yellow wire from ECM to relay. That wire has not connectors between ECM end and relay end to give problems.

215 is fine. They ramped up the fan on temps the next model year after yours. Many cars today don't turn on fan for low speed until it gets to 213-215F
With a pressure cap and coolant there is no boil risk until upper 230's. Radiator tank caps are moving to 150kPa/21 PSI and that pushes boiling to 245 or thereabouts.

I am surprised the temp climbed to 215 at 20 mph. What was ambient temp when you did the testing?

[WhatAmIDoing]

If you have an old fashioned bulb test light you can test for the signal from ECM. If you connect the alligator clip to batt pos and then probe the low speed trigger wire, yellow/white one, then the light should light to indicate the ECM grounding for low speed at 205-210. The signal won't show readily on a DVOM unless it has the voltage present to see the contrast of voltage and then 0.7-1.1 V DC when the ECM outputs ground. The connectors used on that relay for the ECM signals aren't backprobe friendly to check it with the two wire plug connected.
If you ground the two pins and get the two speeds it is leaning to no signal from ECM or problems with the yellow wire from ECM to relay. That wire has not connectors between ECM end and relay end to give problems.

215 is fine. They ramped up the fan on temps the next model year after yours. Many cars today don't turn on fan for low speed until it gets to 213-215F
With a pressure cap and coolant there is no boil risk until upper 230's. Radiator tank caps are moving to 150kPa/21 PSI and that pushes boiling to 245 or thereabouts.

I am surprised the temp climbed to 215 at 20 mph. What was ambient temp when you did the testing?

Ambient was ~85F. I wasn't too surprised with the engine always under load on all the hills. Lots of residual heat and a hot turbo. I figured 215 was not anything to be overly concerned about, going to see what I hit on a 20 mile drive tomorrow through the hills at ~50mph. All I have is a DVOM, but I suppose I could rig a tester with 2 alligator clips and an old light bulb.

[jimmy57]

Yes, that would work. pick a smaller bulb, 5w. A 194 push in bulb would be fine. The power stage circuit for relay is not llikely to be happy with more than
0.5 A

[WhatAmIDoing]

So I'm guessing I have to test this with the engine on and the ECT reading over 205?

[cmblackburn]

Fan relays are known to go bad in these cars. I would make sure you have a low speed signal when you should, and if so switch the relay out. You could also jump power to pin 1 and see if you get low speed fan.

[esl_97_850_T5]

You can command the Motronic 4.4 to test the engine cooling fan using an ELM327 device which is KWPD3B0 capable (eg, like ScanTool.net OBDLink LX BT, OBDLink MX BT, OBDLink SX USB).

See viewtopic.php?f=1&t=78274&p=420879#p420879 post for details.

At the present time, the simplest way to do this is to forget trying to manually issue all the commands in the CODE blocks in the first part of that post, and instead use volvo850diag / Realterm / ELM327-compatible tool (which is KWPD3B0 capable so it can address the M44 as ECU 7A) / MS WinXP thru Win10 / MS IE (IE8 for WinXP and IE11 for WIn7 thru Win10).

Once you get volvo850diag up and running w/ Realterm:

1. Click "Start Realterm".
2. Click "Read All DTCs" and wait for it to complete.
3. Click ECU 7A "Setup".
4. Click ECU 7A "Read DTCs" (or ECU 7A "ATSI") and wait for it to complete.
5. (optionally) Click ECU 7A "Quick Scan" or ECU 7A "Full Scan".
6. Now, once that setup has completed successfully, follow the last paragraph of that post just mentioned. Issue all 3 of the commands in the Realterm Terminal pane.

First issue the ATSH command to get the headers setup correctly:

ATSH 85 7A 13

Then turn the fan on high:

B0 1F 3203

Then turn the fan on low:

B0 0E 3203

The results should be something similar to those in the next-to-the-last CODE block of the MVS post referred to, ie, the CODE block with the ELM327 commands and responses with some explanatory comments added.

When finished, press "Close Realterm" in Realterm and disconnect everything.

I'll see if I can add those two fan control commands as some ECU 7A pushbuttons in the very near future so we don't have to worry about typing them correctly.

esl_97_850_T5

[rspi]

In about 20 P80 cars checked, between '94 - '98, the fan come on at 216 degrees F and goes off at 206 degrees F. In the '99 and '00 cars, the fan doesn't come on until around 225 degrees F.

In the rare times that the temp on my scan gauge II rose above 225 degrees F, the gauge has not moved above 3 O'clock until the temp reached 235 degrees F.

These cars have pressurized coolant system, so if the coolant is in good condition, there should NOT be a hazard of overheating and damaging the head gasket until 275 degrees F.

[WhatAmIDoing]

In about 20 P80 cars checked, between '94 - '98, the fan come on at 216 degrees F and goes off at 206 degrees F. In the '99 and '00 cars, the fan doesn't come on until around 225 degrees F.

In the rare times that the temp on my scan gauge II rose above 225 degrees F, the gauge has not moved above 3 O'clock until the temp reached 235 degrees F.

These cars have pressurized coolant system, so if the coolant is in good condition, there should NOT be a hazard of overheating and damaging the head gasket until 275 degrees F.

Well you're the expert. Fan comes on at 215F and goes off around 200-204F. That fits in pretty well with what you have observed. The dashboard gauge; however, begins to rise from 3 o'clock as soon as the temp exceeds 206F. Highest temp I have observed was 222F, and the gauge was at 2 o'clock, but saw no signs of overheating (not that I expected too, but my passenger insisted I check). Starting to wonder if the idiot gauge is starting to take its title too much to heart. Since my temps seem acceptable, and I know the fan works, I'm going to stop worrying about it. Thanks Robert!