I've been driving my 405 GL since its manufacture. It is a model fitted with air-con.

Five years ago I was forced to replace the entire engine. Since then I have had problems with the cooling fans. Due to a leakage I have also not been able to restore my aircon.

Because of the shoddy work done, I had to download a Haynes Manual in order to get things right again. When the new engine was installed, it took me some time to get the engine temperature gauge to work again. I found out that there are some single pin sensors at the back of the thermostat head.

One lead was connected there initially, but it wasn't showing the temperature. It took me an inordinate amount of time to find out that there are three sensors there and find the right one. Unfortunately, the cooling fans do not work when they should (from various fora and the manual I have concluded that they should work from around 88 to 90 degrees).

I realised that some wire leads had been cut irrespective of their connections to the engine. There are three plugs hanging unused in the engine area. I was also given what seems like a thermistor with the new engine. I cannot tell whether it was part of the old engine or was part of the new engine setup.

I tried connecting it to any of the 3 unused plugs and even used hot water to simulate the hot radiator. It did not work. I have therefore concluded that it cannot be part of the radiator setup as I was led to believe by some info I saw online.

The only info I have seen as credible is this:
You have 1 sensor for the fans & Bitron unit

1 sensor does the temp gauge & ECU (if petrol injection )

The other sensor does the "STOP" & "High temperature" warning lights

Thats why Peugeot 405s have 3 temperature sensors.

Obviously I have found the temp sensor. I attached a wire each to the remaining sensors and connected the "open" wires to the sensors whenever the engine was hot enough but there has been no response form the fans.

he info I found did not say whether the sensors were single pin or double pin. But most fora spoke of double pins which is why I was initially ignoring it.

I have to add that I checked the fan relays, and they are all in proper working condition. I also read somewhere how to make the fans work fast or slow speed and tried it out using a piece of wire. It worked. All that I need now is for the fans to be triggered when the temperature gets to 88 degrees. I think because of the differences in Peugeot engines, I cannot entirely relate the diagrams in the Haynes manual to my car.

For now, I have inserted a wire from under the dashboard with a switch attached to run the fan manually when the temperature approaches 80 degrees. I am an Electrical Engineer by profession, that is why I have been able to delve into the practicalities of the engine myself.

I also cannot locate the Bitron sensor - if my car even has it.

For your information, I live in Ghana. We have a Peugeot dealer here (PRESTIGE Motors), but I live far away from them and cannot take the car there each time there is a fault. I have therefore had to rely on roadside mechanics to help me out.

Fortunately, the Haynes manual has provided me with much info, so I'm able to read and verify things for myself before I go to my usual mechanic. He has also seen that I know enough for him to trust my judgment - even though he does the work!