Thermostat fun on a C3 Picasso

[JoolsPB]

Hi All,

I have a 2012 C3 Picasso 1.6 Vti Exclusive that recently started drinking coolant. No white slop in the oil, but plenty of coolant all over the gearbox which made the thermostat and associated pipework suspects 1 & 2. After pulling the old housing, I ordered a replacement which is physically the same bar the connector that faces the rear that only has two pins, rather than the 4 fitted to the original. The spares shop checked their other brands for similar parts but they all had two 2 pin connectors.

So, my only question is, what am I looking at here? I have searched and found the link listed here:

viewtopic.php?p=678605&sid=6e786ce5a66b ... 6f#p678605

which shows three types. The original looks most like 'B' with the separate temperature sensor screwed in where the bleed screw normally lives but part 'B' only appears to have two wires. The replacement has a bleed screw and a removable temperature sensor like part 'A' but comes with a 4 to 2x2 pin connector adaptor.

Is there a way of wiring using the adaptor that would work? If so, what happens to the extra 2 pins that are on the original part as well as the thermosensor that screwed into the bleed screw hole?~

If anyone has done this change and could help out I'd be grateful. Pics below,

Thanks,

Jools

[JoolsPB]

OK, I now have a part number which is V759927580-06 and apparently, they are as rare as rocking horse poo, there being many variations, but none exactly like it with Eastern Europe being the only place they seem to stock them. I guess I'm going to buying from Poland.

[JoolsPB]

Have taken a multimeter and measured between the pins in the 4 way connector on the original unit. 1&2 have a resisitance of 10.6Ohms and 3&4 measure in at 6.7K. The two 2 pin connectors measure the same as the pairs in the original, resistance wise, so I'm going to go for it anyway and just move the screw in thermistor from the old one into the bleed screw hole on the new one.

If it works, I'll post details for anyone else who ends up in the same position.

[xantia_v6]

The thermostat housing has a heating element (the ≈10Ω pins) and a thermistor.

In some early applications the thermistor was located near the heating element and everything was connected with the single 4 pin connector.

Later, the engineers decided that the thermistor was not in the optimum location and moved the thermistor to the top of the housing (replacing the bleed screw) and added an adapter harness with male and female 4 way connectors and a 2 pin connector to the new thermistor. in this configuration the original thermistor in the thermostat body is disconnected, and maybe the pins are not even present.

Then later the bleed screw was reinstated so the housing had both a bleed screw and thermistor at the top, some of these retained the 4 pin connector (with 2 pins missing), but some (later still?) had 2 2 pin connectors and a different adapter harness (the wiring on the car continues to have the 4 pin connector).

Whichever variant you have, only one thermistor is connected, the other (if present) is not connected.

[PaulC5]

We had a 2010 c3 1.4 vti and when about 4 years old the temp gauge started going to max. The dealer said there was a faulty batch of temperature sensors and the free Citroen official fix was to fit a new temp sensor where the bleed screw was originally located along with a new bit of wiring and the old one left in place but possibly not connected. This fix was a lot cheaper than alternatives of a new housing and labour. From the above posts it looks as if later engines had a modified housing so this could explain the various ones available. This modification to our C3 is explained in the linked post above where it went from type C to type B in the pictures.