Citroen DS electric cooling fan

Published November 8, 2019 · Updated September 15, 2024

The Citroen DS cooling system is somewhat unique in that it relies almost exclusively on pulling air through ducting to cool the radiator. Most cars have a grille where the faster the car moves, the more air is pushed over the radiator. On modern cars this is the grille below the bumper. It is only at idle they only rely on pulling air through the radiator. The Citroen DS has a large plastic fan attached to the camshaft pulley. That fan sits behind the radiator and then pulls air through based on engine speed. The DS21ie and all DS 23 models augment this with an electric fan and an improved radiator / header tank. The Citroen DS electric cooling fan is mounted alongside the mechanical fan (actually almost inside it) and also pulls air through the radiator.

My car, being a carburetor DS21 does not have this improved radiator / electric fan combination. The Citroen DS cooling system worked quite well when the cars were new. However, a combination of the hot Australian climate and an almost 50 year old car that spent quite a lot of time in South Australia means that my cooling system struggles in stop and go traffic. For international readers, South Australia has very hard water resulting in mineral deposits if distilled water is not used.

While I was having some other work done, I had a Davies, Craig fan fitted behind the radiator. This is to augment, not replace the mechanical fan. The setup is basically the same as the Citroen DS electric cooling fan. Over the years people have tried to replace the mechanical fan entirely. This is a recipe for disaster as the electric fans cannot pull enough air at high speed with no ram effect. The Davies, Craig fan is equipped with a controller that allows adjustment of the cut in point.

I also wanted to know when the fan is running. The Citroen DS instrument cluster has an extra warning light that is not used in my car. This is for parking lights. The spot for this warning light was taped up. I have a spare instrument cluster for parts, so I was able to grab another bulb housing to enable this extra light.

Looking at the parts instrument cluster the tape used to disable the warning lights not in use from the factor can be seen. This is at the 12 and 6 O’Clock positions. From there, it is relatively easy to run another wire to the back of the instrument cluster for the warning light. The speedometer cable is already running right past this area. The connections on the back of the cluster are well documented.

I would have preferred a green or orange warning light, but the red one is fine. It works quite well. I took the car for a drive in the 30 degree heat and the light was on for quite a lot of the time, but it did cycle on and off as the fan kicks in/out. The fan is wired to be ‘always on’. This means that after the car is turned off, the fan will continue to run if the engine is hot enough to warrant it. I did this because heat soak can be an issue in these cars. On my test drive, it ran for about 10 minutes after I switched off the car. The risk is draining the battery, but on a hot day this is a useful feature for a short stop.