Engine 850: B5234T/2.3/20v/T5: engine wont start while fan is on

[amazondean]

ok, I am hoping for some advice on an engine related problem. The car in question starts and runs fine until the fan comes on. The car then runs a little lumpy but keeps going. If I switch off the engine the car wont start until the fan has stopped running, which can take some time. Once the fan stops, the car will start as normal.

Any advice on what might be the problem.

[byootox]

the fan doesnt really have much bearing on the starting of the car except for the fact of voltage drop.
Is the engine sluggish to turn over when the fan is on ?

[amazondean]

No. The battery is fine. An odd one this. It might just be that the engine is warm and a coincident that the fan is on

[Joe H]

Originally Posted by amazondean

No. The battery is fine. An odd one this. It might just be that the engine is warm and a coincident that the fan is on

Does it happen exactly or approximately when the fan switches on and off?

If approx. then I would suspect some component is failing as the engine gets hot (=fan comes on) then is OK again as the engine and all sensors and coils etc cool (= fan switches off).

The good thing is that you can make it fail, so you can then go through normal checks to figure out the component.

Joe

[Clogs]

There are usually just three reasons the fan comes on:

The engine is overheated - which can be because insufficient fluid in radiator, fluid not circulating (pump not working or thermstat not opening) or hot weather or just been working hard running up a lot of hills

OR

Air con fluid too hot and in need of cooling - usually because there isn't enough fluid or it's hot outside.

OR

The sensor that makes the fan spin (based on temperature) is malfunctioning

If the first two are OK, then it's the switches / wiring that need to be looked at.

[andrewc1267]

Poss worth checking coolant temperature sensor on live data on diagnosis equipment as if it's reading to cold it will over fuel

[CNGBiFuel]

Poss worth checking coolant temperature sensor on live data on diagnosis equipment as if it's reading to cold it will over fuel

Agreed. Where my money sits. These sensors are known to be troublesome.

[amazondean]

Ok, I have now driven the car home and now know what it is doing. The cars temperature stays in the middle while driving and does not faulter. Then when I got home I switched it off and back on again a few times. The car started fine.

I then left it ticking over for a while until the fan came on. I switched it off and the car still started. I did this a few times and all was well.

Then I switched it off and left it a few minutes and when I tried to start it I noticed the temp gauge stayed at the bottom instead of half way and the car wouldn’t start, just spinning over. Around ten minutes later I tried the ignition and the temp went back to the middle and it started fine.

When I switch the car off the fan stops immediately and doesn’t carry on for a few minutes like I presume it should. I think this is causing the car to overheat slightly, stopping the car from starting. It’s as though it trips something until the engine cools on its own steam.

Does anyone know why the fan is not continuing when the ignition is off?

Thanks.

[amazondean]

Is there anyone out there that might know what is happening here. I believe that when I switch the car off, because the fan switches off immediately, the engines temperature increases and somehow stops you from starting the car until the engine cools slightly.

Does anyone know what might be causing the fan to switch off when the ignition is turned off!!

I have swapped the fan relay and no difference.

Thanks

[Laird Scooby]

Originally Posted by amazondean

Is there anyone out there that might know what is happening here. I believe that when I switch the car off, because the fan switches off immediately, the engines temperature increases and somehow stops you from starting the car until the engine cools slightly.

Does anyone know what might be causing the fan to switch off when the ignition is turned off!!

I have swapped the fan relay and no difference.

Thanks

Yes, it's ignition controlled!

As for the non-starting/cutting out while the fan is running, i'd check the earths behind the left hand headlamp, around the left hand side of the radiator and wherever the fan motor earths. If memory serves correctly, the ignition amp and the fan are earthed fairly close to each other, possibly the same MEP (Multiple Earth Point) and also check the engine to battery earth (usually on or near the starter) and also the battery to body earth.
When i say check, i mean remove the bolts, clean the bolts and ring terminals with a wire brush/emery cloth and also clean the metal where the attach. Refit ensuring they are tight and smear silicone grease (or at a push, Vaseline) over to prevent ingress of water and corrosion or if you have it, dielectric grease.

Also check the wiring to the aforementioned temp sensor and maybe consider replacing it.