CitroJim's AX, C3 Picasso, Cycling and Running Tales

[Stickyfinger]

Do you think you need any bits Jim ?

[Zelandeth]

That's the exact behaviour that led to me fitting g the switch on the front, Jim. Of course it happened in the middle of The Month From Hell when I was virtually commuting between Aberdeen and MK, hence I had no time to look at it. First happed in the Insch Medical Practice car park, and had to be dealt with using naught but what I had in the boot.

I am *really* curious to hear what the cause is, as I couldn't find any logical reason for it looking at the wiring diagrams and what voltages I was seeing at the relay sockets...Granted, I was rather more worried about other things at the time.

[CitroJim]

Do you think you need any bits Jim ?

Yes, a whole fan assembly, casing and loom plus a Bitron ECU Alasdair About the only way I can then guarantee reliable fans again!

I am *really* curious to hear what the cause is, as I couldn't find any logical reason for it looking at the wiring diagrams and what voltages I was seeing at the relay sockets....

So am I Zel, I will get to the bottom of it. Just like I'll get to the bottom of what ails the 207... You're right, it's just not logical... At this time it just makes no sense at all...

[RichardW]

Can't see it's anything other than the Bitron..... unless there's a high resistance to earth somewhere, or the cables are rubbed through and you're getting a spurious voltage on a wire somewhere. Or it's just possessed!

[Mandrake]

I haven't studied the circuit diagrams to see how it's done, but remember chaps that the fans CAN run when the key is turned off, by design.

Normally if the temperature is high enough to trigger the high speed fan while the engine is running, (>97 degrees) the fans will run at low speed when the ignition is turned off, until it cools below the high speed fan cutoff. (There doesn't seem to be a timeout either except cooling down, so it can run for a long time when the coolant isn't flowing!)

From this I presume the Bitron must have a permanent live power supply. So if for some reason the Bitron thinks the temperature is above 97 when the key is off it will run the fans on slow.

I'd identify this circuit that allows low fan speed with the key off and start troubleshooting there. Can you post the full circuit diagram for the fans Jim for a looksee ?

[CitroJim]

Shame is Richard, the Bitron ECU is such a pain to swap, being buried down under the LH headlamp and then under the front plastic panel.. It's a right 'mare to get to, needing most of the front of the car to be stripped!

But I agree, it has to be No.1 suspect...

But, having said that, I know the fan loom is a bit iffy as I've now had to bypass two wires in it.

[CitroJim]

I'd identify this circuit that allows low fan speed with the key off and start troubleshooting there. Can you post the full circuit diagram for the fans Jim for a looksee ?

Simon, yes, I will later...

It is interesting it has coincided with warmer weather but it's not that warm yet!!! I don't' yet know what triggers fan run-on but the fan diagram shows lots of unused inputs into the Bitron ECU which I presume are parts of the aircon diagram. I guess such an input comes from the aircon ECU via a sensor somewhere on the evaporator and this sensor may be the one telling lies and causing to odd behaviour.

I'll get those diagrams up when I can as I'd really appreciate your thoughts on this Simon

[Hell Razor5543]

It isn't only the French who made life difficult for themselves. The mainline WWII German battle tanks were not designed for maintenance engineers. For example, if you had to replace the final drive mechanism (the bits that drove the cogs that pulled the tracks) you had to pretty much strip out the whole of the insides (as they came out from within the tank), and the process was measured in days. The USA made some of their tanks more engineer friendly. On the Sherman tank you uncoupled the tracks, undid four massive bolts, and took the unit off the front of the tank, fitted a new unit, did everything back up tight, and drove away. 1/2 a day, tops.

[Stickyfinger]

It isn't only the French who made life difficult for themselves. The mainline WWII German battle tanks were not designed for maintenance engineers. For example, if you had to replace the final drive mechanism (the bits that drove the cogs that pulled the tracks) you had to pretty much strip out the whole of the insides (as they came out from within the tank), and the process was measured in days. The USA made some of their tanks more engineer friendly. On the Sherman tank you uncoupled the tracks, undid four massive bolts, and took the unit off the front of the tank, fitted a new unit, did everything back up tight, and drove away. 1/2 a day, tops.

Umm, and that was a limiting factor in the design (protection) of the US design.

Was not the case for the Pz4, the similar size German.

Panther/Tiger/Tiger Ausf.B were heavy tanks in comparison to the Sherman/Cromwell's.

Panther & Tiger Ausf.B could have the transmission removed via removable hull plate

[CitroJim]

Surprised the Germans made such a fundamental error as that James! Maybe their tanks were French designed

[Stickyfinger]

In fact the Panther/Tiger.B could use its own Jib to remove its own Transmission.....so not to shabby Jim.

Transmission removal on a Panther AusfG, note the removable deck panel on the ground


Engine deck/Engine change on Tiger.B using the crane mounted via the 'Pilzen' sockets


Modelled for ease of view

[RichardW]

I doubt Jim's going to need one of those to remove the Bitron, but you never know!!

[CitroJim]

I doubt Jim's going to need one of those to remove the Bitron, but you never know!!

It might help Richard Those S2 front bumpers are jolly heavy you know!!!

[RichardW]

Had a look at the wiring diag (a la BOL anyway!) Jim.

All 3 relays are earth switched via the Bitron. Item 1502 (the 'LH' fan relay) on its own, the other 2 together. Only this relay is fed with permanent live (via F14 which also feeds the Bitron). The other 2 are switched live via F2, also fed to the Bitron. Pulling in 1502 causes the fans to run at slow speed. Pulling in of the other 2 relays causes the fans to run at high speed (but requires the LH relay to be energised for them both to run, otherwise only the RH fan will run).

So, either the temp sensor is giving the wrong signal to the Bitron, and causing it to run the fans at slow speed after shut down, or the bitron is goosed. If the former, then I would expect the fans to be running at high speed immediately before shutdown - you would need to get out and see before switching off, or rig up a test lamp to see if you are getting high speed. Allegedly there is a connection to the diag socket, but it comes off the supply to the RH fan, so all it will tell you is if the fans are off, half or full speed. There doesn't appear to be a connection to the Bitron unit, so you can't see what it is doing. Warning lamp appears to come off a different sensor.

[CitroJim]

Thanks for that Richard That's brought out some good stuff as the fans never run at high speed - even with the Bitron sensor disconnected - as the RH and Centre Relay never operate and this I've not yet investigated as I've been so far happy that the fans at least run at half-speed and that should generally be good enough.. I suspect the reason is because of more breaks in the loom.

The LH relay is the only one that operates and my work-around has been to provide it with an ignition-switched supply rather than its more usual permanent live supply which was the last casualty of a break in the loom.

I've not had any opportunity yet to look at the other Bitron connections but my suspicion is that more loom breaks has open-circuited on of its inputs and the Bitron is seeing this as a command to run the fans after the ignition is off. I've not known a duff Bitron ECU itself but there's always a first time I guess.. I have had one in bits out of curiosity once and there's not a lot in there and it's all discreet components as far as I recall and should be amenable to repair with any luck..

I am going to obtain a complete replacement loom and Bitron next month and hopefully after fitting that lot all will be good.