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Old 1 Week Ago   #1
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MPI Sei fan circuit.

Hi all, returning after long hiatus. Finally got my Niece's MPI Schumacher Sei to my house to work on. I'm currently investigating and removing the utter bodge-up of the fan wiring. The wiring from the radiator thermo-switch has been entirely removed and directly wired to the fan and an un-fused 12V feed was supplied from the cabin via a pull switch. Yes, it seems to have been slightly on fire at some point in its past. Questions/observations:

1. What is the relationship between the radiator thermo-switch and the ECU, and the temperature sensor on the head and the ECU? i.e. why is the rad-switch even needed if the ECU references the temperature sensor? It may be that there has been a non-original rad. fitted to my car - nothing would surprise me at this point.

2. Once all the splices/Scotchloks The system appears to be factory wired as per the attached diagram (Yes, I know I draw like a drunk child). The MPI seems to have a constant ground to the fan and a switched 12 V, which is apparently supplied via the ECU actuating the relay. I have verified the continuity on the connections shown. As far as I can see, it agrees with what Honeymonster's findings in this thread.

3. The fan operates when powered directly.

4. The rad-swich wiring is entirely missing. I got (what I thought) was the loom section from the scrappies which has the rad-switch, and it is wired in with the horn on that example. On my car, the horn arrives in a plastic carrier on its own. I have looked inside the upstream loom branches and there is no remnant which I can find.

Assuming the MPI ECU references the head temp. sensor alone to actuate the fan, and the rad. switch is an artefact of having a non-standard rad fitted the wiring is now correct - is there anything I'm missing?

Alternatively, if the rad-switch is also needed, can someone please tell me, preferably with the aid of a photo, where the rad-switch wiring goes.

Many thanks in advance for any assistance.
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Last edited by Jamieboy; 1 Week Ago at 23:11.
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Old 1 Week Ago   #2
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Re: MPI Sei fan circuit.

Im pretty sure the mpi sei fan is controlled by the ecu... check out the download section on the forum for the seicento service manuals... there will be wiring diagrams and the likes in there that will help you no end
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Old 1 Week Ago   #3
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Re: MPI Sei fan circuit.

Quote Originally Posted by Lecook View Post
Im pretty sure the mpi sei fan is controlled by the ecu... check out the download section on the forum for the seicento service manuals... there will be wiring diagrams and the likes in there that will help you no end
Thanks for the reply. ECU-controlled relay to fan was my understanding too but the diagram in the service manual seem to be for SPI only unfortunately.
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Old 1 Week Ago   #4
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Re: MPI Sei fan circuit.

Ahh i see... i have an mpi ms edition too.. but fortunately mine hasnt been bastardised... what exactly has been replaced on yours?? Has the fan been replaced with a spi item or an spi rad fitted??
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Old 1 Week Ago   #5
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Re: MPI Sei fan circuit.

Quote Originally Posted by Lecook View Post
Ahh i see... i have an mpi ms edition too.. but fortunately mine hasnt been bastardised... what exactly has been replaced on yours?? Has the fan been replaced with a spi item or an spi rad fitted??
It's a possibility the rad. has been replaced by an SPI unit. I am wondering - does your rad have a thermo-switch on it? If so, could I ask, when you have a moment, to document where the wiring goes. It's not at all clear from the loom on mine if the wiring has simply been cut and tucked away or if it should indeed not be there.

If there is no rad-mounted switch, my guess is that the temperature sensor in the head is monitored by the ECU and the fan relay is actuated at a set point.

The whole thing has been a cowboy job by the looks of it.
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Re: MPI Sei fan circuit.

Ill see if i can get to the car tomorrow and ill get some pictures... i cant remember off the top of my head if ot has the switch on or not...
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Re: MPI Sei fan circuit.

Quote Originally Posted by Lecook View Post
Ill see if i can get to the car tomorrow and ill get some pictures... i cant remember off the top of my head if ot has the switch on or not...
Thanks so much; that's really appreciated!

Night!
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Old 1 Week Ago   #8
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Re: MPI Sei fan circuit.

The green plug near the thermostat is the warning light iirc and the block temp sensor on the back is for the ecu i think. No sensor on the rad like a Cinq. A little Fiat cost cutting and no temp gauge!

I guess you dont need a gauge until the car gets older...

Oh and I notice the rad fan does not stay on after you switch the ignition off, as I think it did on the cinqs?

Do you think the switch was a botch for a tired radiator?
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Old 1 Week Ago   #9
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Re: MPI Sei fan circuit.

There should be no fan switch on the rad, it is definitely ECU controlled. The fuse for the fan is behind the battery.

Its quite well hidden so possibly a previous owner was unaware of its existence.

The Sei manual in the download section has wiring diagrams for both SPi and MPi.

Cheers

D
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Old 1 Week Ago   #10
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Re: MPI Sei fan circuit.

Quote Originally Posted by purf View Post
The green plug near the thermostat is the warning light iirc and the block temp sensor on the back is for the ecu i think. No sensor on the rad like a Cinq. A little Fiat cost cutting and no temp gauge!

I guess you dont need a gauge until the car gets older...

Oh and I notice the rad fan does not stay on after you switch the ignition off, as I think it did on the cinqs?

Do you think the switch was a botch for a tired radiator?
Yes, it seems a bit cheap. I think the rad-swap was to make up for an inoperative fan or indeed a tired radiator.
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Re: MPI Sei fan circuit.

Quote Originally Posted by rallycinq View Post
There should be no fan switch on the rad, it is definitely ECU controlled. The fuse for the fan is behind the battery.

Its quite well hidden so possibly a previous owner was unaware of its existence.

The Sei manual in the download section has wiring diagrams for both SPi and MPi.

Cheers

D

Thanks for the reply. When I originally found the 30 A Maxi fuse, it was blown and there was definitely scorching to the upper bulkhead and scuttle panel which I think has been from a small fire as a result of the awful work that has been done in the past.

It's very good to know that there should be no native switch on the radiator. I can safely leave this disconnected, stop searching for missing wiring and instead turn my attention to the temperature sensor on the inlet manifold and probe its reading using Multiscan.

Thank you also for confirming that the Sei manual also has MPI wiring - I will revisit that; careless of me to miss it.

I'll post my progress.
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Re: MPI Sei fan circuit.

Just to confirm what others have said, mpi has no rad switch.

the seicento technical manual is great, will have all teh wiring diagrams you need to put this back how its meant to be
What purf said sounds wrong to me though regarding which sensor is which, I believe its the other way round... the sensor on back of the head at belt end is the temp sender for dash i.e. an ON/OFF switch for the overheating warning light. The green sender by the stat is for ecu engine temp.
I'll admit I have never personally had an mpi one but on a spi the sensor on the back of the head is for the warning light, and on a cinq its the varying resistor type for the temp guage. On both the spi sei and cinq the ecu temp sensor is blue and on the inlet manifold and its equivalent is the green sensor by the stat on an mpi.

Hope all that made sense. lol
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Re: MPI Sei fan circuit.

You are right blu. Thanks for clearing that up
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Re: MPI Sei fan circuit.

Looks like someone in the past has fitted an earlier rad to yours - not a bad thing!
The MPI/ECU operated arrangement cuts in very high - (dangerously so IMHO) - with the torque app running on my new Sei - it cut in at 99 degs! (my other SEi cuts in around 98-99 also)
If you run a non ign supply to fan sw (via say a 10A fuse) - from battery would do as like the Panda(old) fan is not ign controlled - and other to earth (body) you will find fan will most likely come on via rad sw. first - belt and braces

See thread 'meanwhile' for how I fitted manual o'ride sw on my Sei (this gives advantage of keeping your fan nice and free if you rarely get up to 'fan cut in' operating temperature) - a job I'll def do on my latest Sei
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Old 1 Day Ago   #15
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Re: MPI Sei fan circuit.

But an old rad from a Cinq might not be working very efficiently if it's old and gunged up. I reckon My sei would benefit from a new radiator.
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