Radiator E-Fan manual control isn't working(?)

[eddiehumpf]

Hi everyone,
I bought recently my first Volvo, a 1998 940 2.3 LPT from the Celebration series. Now that I've worked through the three oil leaks that it had, I am plagued by a new issue, overheating.

Essentially, it keeps overheating in traffic, and this is due to the radiator fan not switching on. Before anyone mentions temp sensors, the E-Fan in my car has been wired by a previous owner to be manually controlled by the three pronged switch on the dash (used to control antenna?). I've followed the wires from this into the engine bay, and found that one has come undone. I don't know what approach they took to wiring this, but I just can't figure it out.
The pictures I've attached are:

1. The wiring of the switch
2. One wire connecting to the underside
3. One going through the bulkhead
4. The end of the wire

I've tried plugging the end of the wire into the 1 and 2 slots, no success. All the fuses are also intact.

Any help would be great!

https://drive.google.com/drive/folde...BP?usp=sharing

[Rversteeg]

Apparently you still have the standard E-fan relay controlling the fan. This is a double relay, with one coil for low and one coil for high speed.
By either grounding the connections marked IN 1 or 2 of the relay, you can have the fan run at high or low speed. Your predecessor has replaced the wire to IN 1 to control the fan. This wire is grounded via the dashboard switch.

If you directly ground either IN 1 or IN 2 the fan should start running. If so, the problem is in the DIY wire or dashboard switch.
If only grounding IN 2 starts the fan running, the problem is probaly in the no. 1 coil of the relay.
If there is no 12V feed on the single red wire connection 30 the fusible link has probably blown.
Finally it could also be the fan itself that has failed.

To try to revive the original E-fan control I would also check the wiring to the ECU in the drivers footwell area, by measuring or bypassing with a temporary wire from the dashboard switch. The ECU takes its temperature reading from one of the two sensors below the inlet manifold. This sensor could be defective as well, although this will also have a negative effect on fuel economy.
Another solution would be to add an additional temperature switch with its feeler on eg the bottom hose to the radiator.
https://www.conrad.com/en/p/kemo-m16...-c-191249.html

Personally I would not want to rely on a manual system, as my car is also used by other drivers than myself.

BTW, switches 7/38 and 7/40 are mounted in the A/C condensor, so only applicable if you have A/C.

[eddiehumpf]

Thanks! It did end up being the switch on the dashboard having issues. Next job is to revert it to automatic control.