Fan check test

[Chuggaboom]

With the ignition on I was told to pull the connector passenger side above the temp gauge supply.

Result: Both fans running, looking fwd, LH clockwise and RH anti-clockwise.

Is this as it should be !?!?

[pmessling]

Are the fan blades at the same angle.

[Steve_T]

Can you not tell if both are sucking air into the engine bay? If I remember right the connectors have blades at 90 degrees to each other so you can only connect them one way around.

[ukkid35]

Chuggaboom said:

With the ignition on I was told to pull the connector passenger side above the temp gauge supply.

Result: Both fans running, looking fwd, LH clockwise and RH anti-clockwise.

Is this as it should be !?!?

Yes, the AJP8 has two different fans that rotate in different directions, with the larger fan coming on first, and the slimmer fan coming on second.

On my car there is a sticker on the slimmer fan showing direction of rotation, there may have been on the larger fan originally as well.

[ukkid35]

Also worth adding that with some cars you can't force the fans to run unless the engine revs are above a few hundred. This is an optional mod included by Joolz to reduce battery load when starting the engine. I thought my MBE was broken until I found that out!

[Chuggaboom]

Yes looked again and the blades different direction. Repeated test and both fans pulling air into the bay.

So next question is why when it hasn't lost any water does it start to overheat when idling ?

[ukkid35]

Possibly partially blocked radiator, possibly faulty coolant temp sensor.

What is your definition of overheating?

[Chuggaboom]

Gauge normal 90-95-100 depending on traffic speed....get home idling on drive goes up to 110-115 and audible hissing.

[mike_e]

Temps seem a little high, mine ran around 90 on the road and up to 105 in traffic and you could definitely hear the fans cutting in when stationary. You didn't mention if your fans cut in automatically when hot and idling, they should do periodically. Disconnecting them doesn't tell you if the thermal switch which triggers them is working correctly, it just shows the fans are capable of running. Check the switch if they don't cut in.

[ukkid35]

You can't trust the dash gauge to give you the actual temp, only the change in temp.

You are better off using the Laptop Diags, or better still the RS_AJP. However even that can be wrong if the temp sensor is faulty or the connector is corroded.

So, best get the sensor replaced, and connect up the RS_AJP.

The fans will tell you what the engine thinks the temp is, because they will come on at the temps set by the MBE, although I can never remember exactly what they are as standard, and there's always the chance they could have been changed if the car has been remapped.

If everything is working correctly you should be able to leave the car idling and it should cycle through with the fans coming on and then going off again once the temp is brought back down.

[mac315p]

Chuggaboom said:

... and audible hissing.

Always difficult to diagnose via the interweb but the audible hissing would be a concern for me. . . Could this be due to excessive pressure in the coolant system?


Regarding fan temps I think the figures quote in this thread are about right.

Tanguero said:

First fan on at 90 second fan on at 95 is standard I believe. If you have had Joos cooling chip modification in the past then it will be 82 and 85 I think, certainly in the 80s somewhere.

[Chuggaboom]

I was told the ECU makes the fans cut in at 92 and 97, but lets not split hairs.

Defo one fan was working as could hear it over the engine but the 2nd smaller quieter not so sure. Need to do some more investigating at the weekend.

Understood about the gauge accuracy, well its a TVR FFS, and yes it is showing the change in temp but who knows actually from what to what.

So sensor probably on the shopping list....what mundane car is it from ? Part No ? Choice of makes ? Suppliers ?

[Juddder]

Just in case anyone else fancies a bit of detective working helping out the on and off temperatures, these are the values I have from 3 different ECU EPROMs

[address location provided by Mike SR who worked with Jules on this, from our email chats back in 2015]

1. ECU EPROM version 94110035 V8 (think these are stock values)

Main Fan: On = C3, Off = C0
A/C Fan: On = C6, Off = C1

2. ECU EPROM version 94130101 S6 (think these are stock values)

Main Fan: On = C2, Off = BF
A/C Fan: On = C6, Off = BF

3. ECU EPROM version 92810274 V8 (custom values I believe)

Main Fan: On = B9, Off = B7
A/C Fan: On = BA, Off = B7

I converted them to Dec initially and dropped 100 of the value, which would give, for example, 95o on for the Main Fan in example 1 and 98o on for the A/C Fan with turn off at 92o and 93o respectively, but no idea if that logic is correct

Cheers

Alex

[RUSSELLM]

If you want to test the fans individually, I found it easier to just bridge the relays

[Juddder]

Just to update my own posting, I think the hex numbers in the ECU for the Fans might be temperature in Farenheit

This would make a correct correlation that on for factory default is about 90-92oC and off at 89oC

Modified ECUs are set at 85-85.5oC on and 84.4oC for off

I'm guessing the 1 degree different between the main fan and the A/C fan is to save a bigger surge on the battery if both started at exactly the same time.

Release	Main Fan On	Main Fan Off	A/C Fan On	A/C Fan Off
Stock V8	C3 = 195 (90.5)	C0 = 192 (88.9)	C6 = 198 (92.2)	C1 = 193 (89.4)
Stock S6	C2 = 194 (90)	BF = 191 (88.3)	C6 = 198 (92.2)	BF = 191 (88.3)
Modified V8	B9 = 185 (85)	B7 = 184 (84.4)	BA = 186 (85.5)	B7 = 184 (84.4)

[TheRainMaker]

Could be worth changing the rad cap, mine went, you could hear hissing and it started to over heat.

[Chuggaboom]

Well apparently the issue has turned out to be never bleeding the system properly 2 years ago when fitting the alloy rad ! No that is what I call a slow burn fault !!! Which had matured because of a weeping top rad hose joint, and an old cap, leading to loss of fluid being replaced with air that migrated around to the rad, hence poor cooling efficiency.

So say with the cooling system rebuilt, refill from the reservoir until brimming and leave cap off, bleed the cyl head water rail taps, and then the rad....but if you only spend 5 mins to do this part you will not have done it properly as AJP's are a PITA to refill properly.....I was told more like over half an hour bleed rad and top up reservoir.

Start engine and run till hot and fans cut in and out to test. Leave to cool and top up system next day....I was told expect anything up to a litre.

Lazer temp gun in the thermostat housing area showed I have a gauge that reads 7 deg hot...fine now known.


Next job....starter motor needs looking at....makes not nice noises when used from cold....needs stripping and bearings re-greasing apparently.

[ukkid35]

There is no bleed hose from rad to expansion tank in the Cerb, so the coolant level in the rad drops before you can see the level in the expansion tank drop.