radiator fan low speed not working

[lloydy]

Hi all, Have noticed since getting my van back from engine conversion that it tends to run hot when sitting in traffic.

Needle on gauge goes a fair way past the led then high fan speed kicks in. So after doing a bit of reading on here, pulled the connector off the rad fan switch and bridged inner to outer spade terminals. On the high speed side, i can hear the fan kick in, on the low speed can't hear anything. So is this just a new fan? or is there something else to check first?
thanks, Lloyd

















nee

[AdrianC]

Hi all, Have noticed since getting my van back from engine conversion that it tends to run hot when sitting in traffic.

Needle on gauge goes a fair way past the led then high fan speed kicks in. So after doing a bit of reading on here, pulled the connector off the rad fan switch and bridged inner to outer spade terminals. On the high speed side, i can hear the fan kick in, on the low speed can't hear anything. So is this just a new fan? or is there something else to check first?

I've just been looking at this today, since I had very similar symptoms (but didn't wait for the high to kick in - if it would've). Fortunately, kicking the heater onto full hot and high fan brought it down to just above the LED, even trogging up mountains.

According to the Bentley wiring diagram, both use the same fuse - so that must be good. The low speed is wired directly - fuse->switch->motor. The high goes through a relay between switch and motor, so that's more complex. Fortunately, mine's working on both low and high by bridging the switch connector, so it's gotta be the switch.

Have a dive underneath the front, and bodge some +12v and earth to the fan connector - if it works there, you've got a wiring issue. If it still doesn't, then it's the motor. Mind you don't get your fingers in the blades...

As a bodge-around, mebbe swap the low and high-speed wires around, so you're just going straight to "hovercraft mode", but without getting the teabags ready first?

[syncroandy]

On the thermoswitch terminal housing, pin 3 goes to battery via fuse S1, pin 2 is the 95 degree switch, and pin 1 is the 102 degree. The circuit for the 95 degree switch then goes to the series resistance (so the fan runs at a reduced speed). So if you're bridging pins 2 & 3, and the fans not coming on, it could be the series resistance (or wires to/from it) stopping the fan running.

I'm a bit surprised your fans coming on, was that a high-speed run followed immediately by hitting stationary traffic ?

[lloydy]

I first noticed it earlier in the week, as after you say a fast run then parked on the drive. Temp rose until high speed fan kicked in, sun was beating down on the front of the van though. What i'm finding now is driving at any speed, say 10mph to 70mph the gauge stays left of led. As soon as i stop in traffic for more than a few minutes it will start to rise. I got stuck in traffic yesterday (very hot weather) after a hour motorway drive, and the needle creeped to the right until it was past the led

[jed the spread]

I too am surprised it is getting that hot, my water temperature has never gone over 75*c and I cant think my fan has ever come on, even doing Stratter Florida. The TDIs run super cool.

Was it bled properly?

jed

[lloydy]

Was it bled properly?

jed

probably not, as you know, he didn't put any coolant in it so i have to drain and put some G whatever in. Rad gets hot though, very hot. Still, the low speed setting on the fan doesnt seem to work. And i do remember 'him' saying that he really struggled to get the rad back in due to the chargecooler, maybe he knocked something off. So, bashplate off tomorrow and see if i can get to the fan and try to get it working. To be honest though even the AAZ had no problem sitting in traffic

[syncroandy]

Lloyd, can you put up a pic of your accessory belt ?

[ninja.turtle007]

I too am surprised it is getting that hot, my water temperature has never gone over 75*c and I cant think my fan has ever come on, even doing Stratter Florida. The TDIs run super cool.

Was it bled properly?

jed

Mine runs at similar temperature to yours Jed. But I found when it is cold outside the heater blows itself to Luke warm.

Correct me if I'm wrong but aren't they supposed to run at 87C?

Mario has replaced the thermostat to see if it makes a difference.

[camper]

Regarding the engine conversions are you fitted with external oil coolers?.

[lloydy]

Lloyd, can you put up a pic of your accessory belt ?

Not brilliant photo's. Hope you can see whats what.

[lloydy]

I too am surprised it is getting that hot, my water temperature has never gone over 75*c and I cant think my fan has ever come on, even doing Stratter Florida. The TDIs run super cool.

Was it bled properly?

jed

Mine runs at similar temperature to yours Jed. But I found when it is cold outside the heater blows itself to Luke warm.

Correct me if I'm wrong but aren't they supposed to run at 87C?

Mario has replaced the thermostat to see if it makes a difference.

The bit of reading i have done says the same. But i'm also wondering that if the timings off, could this make it run hot? To be fair though, if the low speed fan worked, it would not be getting hot. Its only in stationary/very slow moving traffic that i've noticed it move. At the weekend, it went just to the right of led and no higher. Which if i remember from when i had my gauges fitted is below 90. (as this is where my AAZ sat most of the time) .
So temp wise i think i'm ok? Will have a look at wiring to fan a bit better this afternoon

[lloydy]

Regarding the engine conversions are you fitted with external oil coolers?.

some of us are, some of aren't (i'm not)

[Cableguy]

Could something have got disturbed when dash taken out/put back?

[lloydy]

I don't know. I'm going to check the wiring under bashplate and also the back of the connector for the rad fan switch.
Hopefully I'll spot something. It's one problem I could do without at the moment. The list is growing

[syncroandy]

Thanks for the pics Lloyd, it was just that a silly thought went through my mind. The Passat water pump runs the opposite way to 'older' TDI's and if the PAS pump was deleted it possible the pump might have been being driven backwards. The PAS pump is there though.

(BTW, might be worth securing that cable that looks quite close to the belt so it can't make contact.)

Re. temps. I use a Scanguage to monitor stuff whilst driving (via OBD). The water temp is shows me is that seen by the ECU. I have the standard 87 degree thermostat, and I find temps are generally between 85-90, I can't recollect seeing it over 90. Oil temps (VDO gauge on dash) are close to the water temps, no more than 80-90 max. I therefore don't believe a cooler is needed. I have the larger AFN heat exchanger which may help.