I discovered to today while driving a P38 4.6 Motronic/Thor from a friend, that the air con fans cool down the engine, after it has been switched of. Nice feature, which I always wanted on my own GEMS V8. Now I compared the Electrical trouble shooting manuals of my model year (98 VIN WA) to the 99 onwards ETM and both say the air con fans will be running after engine is switched off, for cooling purposes? Does the GEMS Efi has this feature? There are three relays on both models (13/14/18) which I do maybe understand, but I never experienced my fans running after switching off the engine (or I never heard it?) ... I will test according to the ETM the function of the relays and fans tomorrow on my car, but any hints/tipps on this subject are highly appreciated! happy rangerovering

I have a feeling I've seen this question before.....

They will do it on a GEMS too but only if the engine temperature is high. My car runs fairly cool, rarely, if ever, getting over 95 degrees C and I've only ever heard the fans kick in once while it was idling when I was calibrating the EAS. However, with the current heatwave affecting most of Europe at the moment, I don't know about the electric fans but my viscous has been locking up regularly, I can hear the jet engine noise it makes when pulling away if I have been stationary for more than a couple of minutes. It would be interesting if you used diagnostics to check the engine temperature on your car and the Thor to see what the running temperature is.

Hi Richard, yes I crossposted it 😉
Temperature was between 91 to 95 C after long incline and 30 C outside.
I always liked the idea of using electric fans for cooling, when the engine is switched off. I know it from VW and Audi.
Now I discovered that the P38 has this already …
BTW as You changed Your gearbox… the THOR 4.6 drives impressive, but as smaller TC fitted like in our 4.0 has the same rpm like mine, when in TC mode. The bigger TC You have fitted should have a lower rpm. I can compare now 4.0 and 4.6 GEMS and 4.6 THOR.

My original gearbox always seemed to change up at lower revs than I expected and was reluctant to drop down a gear when climbing a hill for instance, I had to give it plenty of throttle to make it change down. The Ascot, a 4.6 GEMS, changed up at slightly higher revs (around 2,000 rpm compared with 1,700 on my original box) and would drop down a gear far more readily when needed. My car now drives much the same as the 4.6 (if not better) although I don't know if this is a difference between the two gearboxes and torque converters, my original box had been on its last legs since I've owned the car or if the fact I am now running a 4.6 gearbox ECU and the original one had been re-programmed to meet the requirements of the original owners (Greater Manchester Police) I have no idea. The larger torque converter means I now have effectively a heavier flywheel so I thought that might make it feel different, but it doesn't seem to have done.

The gearbox supplier has fitted the 4.6 gearbox to over 30 4.0 litre cars over the years and has always left the original 4.0 litre ECU in place. I suspect the only difference is the range over which adjustments to suit driving conditions can move. I will admit that mine is now so smooth when accelerating with the rev counter just hopping between 2,000 and 2,200 rpm as it goes up through the gears but the changes can't be felt at all.

Going back to the original subject, I'm about to go out in mine and it is already up to over 26 degrees outside, so I'm going to monitor the engine temperature and see what it is running at now.

Hi Richard,
on topic: Checked the fans and relais on my car, they work as intended. Never noticed them running after switching off the engine on hot days before, in my own car.

Off topic @gearboxes, tcs and engine sizes… interesting and valuable observations, thanks.
I have a slightly different situation with my own 4.0. It shifts at higher rpm, than a 4.6 GEMS (big tc) and comparable to 4.6 THOR with the smaller tc (like the hp22).
My suspicion is the bigger tc gives the lower rpm?

I checked the running temperature on mine yesterday out of interest. Driving back from Paris and the exterior temp display was showing 32 degrees C. Running on the motorway the coolant was at 91 degrees, slowing down in town traffic it rose to 93 so no need for the fans to come on at any time.

One thing I did notice was that my blowers aren't adjusting with sunlight. In the past I've noticed if I get in the car when it has been parked in the sun, the blowers start up then after a few seconds speed up to get the interior temperature down. Once the interior is getting comfortable the fans slow down but will speed up when the sun hits the sensor on top of the dash and slow down again if in shade. At the moment it isn't doing that so there's a problem with either the interior sensor or the sun sensor. Fortunately, the Ascot works as it should so I'll get the Nano out and compare the readings on both cars. I think the interior sensor is working as it should but no idea if the solar sensor is and as the Nano reads it out in w/sqm, I've no idea what is correct and what isn't.

Hi Richard, the solar sensor can be triggered by a really bright torch light, I was told. Maybe You can test, if the Nano shows the alteration? Iirc the test was, as You described, to point a torch light to the sensor and the fan speed should increase.

This gets even curiouser. Driving it yesterday the blowers were running at half speed but I went round a tight RH bend with a bump partway round and the blowers suddently went to full speed. This suggested a bad connection somewhere. Checked the readings from the assorted sensors and compared them with the Ascot, all virtually the same. Solar sensor was giving readings close to 100 but dropped if I put my hand over it yet the fan speeds didn't change. So, out with the HEVAC and have a good look at it. Spotted what might have been a dry solder joint on pin 2 of C245 which feeds the RH blower so re-soldered that. Gave all connectors a good dose of contact cleaner and put it back in. Now the blowers are running at half speed but if I manually turn the blower speed up, they go to full tilt as they did anyway but stay on full speed if I switch back to Auto. They will also slow down if I cover the solar sensor so seem to be working properly as long as I manually put them on full speed before switching to Auto. Very odd.

I can't swap the HEVAC between the two cars as I modified mine some years ago. I had an intermittent fault which was a bad connection on the main power feed plug into the HEVAC (C244). So I soldered flying leads to the connector pins and put an inline plug and socket on it. That has worked perfectly for at least 10 years but it means that I would need to do a similar modification on any replacement HEVAC.

Yesterday with 30C outside the electric fans were running, but in slow mode.
Speed was mostly in TC mode in a hilly valley, so load on the engine and not that much cooling by „breeze“ ;-)