1996 Volvo 850 GLT N/A - Engine cooling fan doesn't run

jragone · Post by **jragone** » 25 Jul 2025, 09:05

I'll add more context below, but here's the short of my question: can it still be a sign that the engine cooling fan is busted if it doesn't run when jumped but does run with the ECT sensor unplugged?

My engine cooling fan isn't running, and it's giving me a major headache with the near-100-degree heat in the midwest recently.

A few weeks back, my engine temp got a bit above 3 o'clock on the gauge. I pulled over to let it cool and noticed a small hole on the expansion tank nipple that was hissing coolant vapor. The coolant system was almost all original to the car, so I decided this was the time to replace it. I replaced:

Expansion tank

Expansion tank cap

Expansion tank sensor

Rubber hoses

Thermostat

Radiator

I flushed the system with water a few times and filled it with a coolant mix. One week later, the car started blowing coolant out of the cap right after a drive. So it was clear to me I had not fixed the root of the issue.

I noticed that the fan wasn't running when I turned the AC on, and I could hear the compressor cycling on and off every 5 or so seconds. I read in a few other posts like this one that the ECT sensor was the likely culprit. And given that the fan could run with the ECT sensor unplugged, I decided to order a new OE sensor. I found while replacing it that the female connectors for the sensor had corroded, so I spliced and replaced those with these female bullet terminals from Dave Barton.

Still, the fan would not run. So I started to look at the fan relay. When I banged on the relay, I heard a click and saw the fan blades jerk slightly. Thinking the relay was bad, I ordered a new OE one and replaced that. But again, the fan would not turn on, regardless of whether the AC was turned on or the coolant was hot.

Now I'm nearing my wits' end. I followed Robert's video to jump the high and low-speed leads, and it sounded like I got a couple starting kicks out of the fan. But I didn't get any more movement after that. I also followed scot850's steps to ground the middle connector that attaches to the relay, and I could hear the relay click. But the fan didn't spin.

What's weird to me is that it seems like the fan is busted. Jumping the relay pins should have turned the fan on, but they didn't. Though when I unplug the ECT sensor, the fan kicks on at what I assume is the high speed. It doesn't sound as pretty as the fan in Robert's video.

Despite the behavior with the unplugged ECT sensor, my gut says that the fan is the issue. But this is becoming a rabbit hole of replaced parts, so I wanted to post and see if I'm looking in the right direction.

Post by **scot850** » 25 Jul 2025, 13:21

If you jump the ground and power wire on the fan and you get nothing, then sorry, but sounds like the fan motor has failed. Not a common failure but at this age it can happen.

Neil.

Post by **Chuck W** » 25 Jul 2025, 16:30

I'm going to guess it's the fan itself.

Odd that it turned on when you unplugged the ECT, but seeing as you're replaced the relay (and verified that the connector/connections were good and clean), I would mostly rule that out as the culprit.

jragone · Post by **jragone** » 31 Jul 2025, 21:04

Thanks all. I've got a new fan on the way, and I've been tinkering with the fan some more in the meantime. The fact that it could run with the ECT sensor unplugged was bothering me, so I tried grounding the middle connector pins again. To my surprise, I could turn the fan on in both the low and high-speed modes. The coverings on my female connectors have degraded, so I could ground it directly from the exposed copper wire at the base of the connectors. This didn't work when I tried it a week ago. That was after trying to jump the fan's pins directly to the battery.

This gives me some hope that I can get the car back in service sooner than the new fan will arrive (end of August). I'm horribly novice with electrical work, but could this mean the fan's ground is bad? I bought a cheap multimeter from harbor freight and am going to test a few things:

Resistance of the ECT sensor compared against those in this post

Voltage of the live wire going to the fan relay

Trace the fan ground

See if there are any OBD II tests I can run/live data I can read

Anything else worth checking?

Post by **abscate** » 01 Aug 2025, 03:46

The Oem fan 9497929 is no longer made at Volvo but the good news is it’s a p80 model part spanning 1992-2000 models.

As Professor Potato teaches us, two words , “junk yard “

Four seasons makes an aftermarket for $130 if you hurry and beat the consumer import tax, it’s part number 843-05100704

jragone · Post by **jragone** » 20 Aug 2025, 07:48

I gave a new fan a go, but no luck. Weirdly, while I was waiting on the fan, the old one started working perfectly for one week. I could flip the AC switch on and off and see the fan start and stop. It also engaged when the engine heated up and the AC was off. All I did was a drain and fill of the transmission oil, so I'm not sure what got the fan going or stopped it.

The fan's ground is good, but I'm suspicious the ECU isn't signaling to turn the fan on. I don't hear the relay click when I turn the AC on, and I can still ground the signal pins and see the fan turn on. I checked the resistance on the ECT sensor when the engine was recently run, and I read around 150 ohms. That looks right to me.

I pulled the ECU and sprayed the male and female connectors with some electrical contact cleaner. If that doesn't help, I'm thinking to grab a used ECU from ebay.

Post by **scot850** » 20 Aug 2025, 08:28

Have you checked the fan relay and wiring on the top of the radiator? The wiring connectors and the relay can go flaky.

Neil.

jragone · Post by **jragone** » 20 Aug 2025, 12:47

Yep the fan relay is new, and the yellow & yellow-white signal wires were a little corroded near the connectors to the fan relay. So a few weeks back, I cut the wires back until I couldn't see any corrosion and spliced in new wires w/ connectors.

jragone · Post by **jragone** » 03 Feb 2026, 06:29

To close this out, I eventually got to the root of this and found the issue to be my impatience (as well as the original cooling fan.) I hadn't had an overheating episode since I put the new fan in, but I also hadn't seen the fan run when I thought it should. So I threw up my hands and brought it to the dealer, with hopes that they would sort it with some special diagnostic equipment.

Hours later, I received a video of the fan running, and the tech noted that it takes a while to trigger the fan due to the higher volume of the do88 radiator I put in. So it does appear that the final issue was my old, original cooling fan. I have the four seasons fan in there now and managed to snag the OE fan from IPD at ~$300 back in the summer. I'm planning to drop that in there when the weather improves and keep the four seasons as a backup.

I also want to note that the non-turbo do88 kit that FCP sells comes with the turbo upper and lower radiator hoses. I had to buy the non-turbo ones separately, but I didn't notice this discrepancy until after I tore open the packaging. So if anyone's running a turbo and wants to swap out their radiator hoses, I'd be happy if you could take these off my hands! Maybe $80?

Post by **scot850** » 03 Feb 2026, 08:05

Definitely an new one on me. Thanks for getting back and closing out on the issue. Point noted on the higher efficiency Do88 radiator. Probably aggravated by the car being an NA which don't work the system as hard as a turbo.

Neil.