My nerves and the otter switch are in constant battle- probably because on at least one occasion the switch has failed. I have renewed the otter switch but somehow I can't quite bring myself to trust it fully and sitting in traffic is pure torment. I find myself watching the temperature gauge and waiting for the fan to switch in. However, as things stand there is nothing I can do as the temp creeps up and I can't tell if the switch is late until its too late! What I therefore need is firstly a monitor light which will activate whenever the fan is active and a bypass switch that will allow me to turn it on manually if I suspect the motor is becoming too warm. This is also useful to decrease the motor temp just before parking as the fan will not operate once you have parked and the ignition is off, Leaving the motor with a heat build up just as you park isn't necessarily a good idea- I note modern cars do have fans that can run on after the motor is off.
The wiring diagram shows that the otter switch functions to connect a yellow green (YG) switched power feed to a brown/orange (BO) wire that earths via relay no 3. This closes the contacts and energises the fan. Power flows from the relay to the fan motor through a thicker brown and black (NB) wire.
In order to fit a bypass switch I need to connect a jumper switch between the YG and BO wires. I could connect this from the otter switch itself, but these wires are also accessible at the relay, and connection here would be neater. However the relay connections are all hidden away behind the fuse panel in the drivers footwell, and access is as always, very tricky! To get at least some chance of making these connections I unscrewed the 2 x 10mm bolts that secure the fuse panel.
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| Fuse panel is held by two 10mm bolts- lower one has been removed already |
I was able to reach through and tease out the two B/O wires entering the relay
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| Fingers have just managed to grab the two BO wires |
These wires are very tight and have virtually no slack. Cutting and rejoining will be very difficult. I was able to get the automatic wire strippers in to reach the wires and open up an internal gap in the insulation to which I could connect a red fly lead as an internal splice and then wrapping the join in insulating tape.
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| Fly lead for switch bypass- still to be wrapped in insulating tape. |
If you look closely in the pic below you can also see the thicker brown and brown/black wires that also connect to the relay and supply power to the fan. Both are positioned just below the red fly lead connection shown above.
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| Fly lead for switch bypass- note thicker brown and brown/black wires (power feed to fan motor) below fly lead connection- again access is awkward. |
I created the warning light connection by making an internal break in the insulation of the brown/black (relay-to-fan motor) wire in exactly the same manner as that in the BO. I could then bring this fly lead forward, adding a 0.1a in-line fuse and connecting it to a warning light. I connected an earth to the other side of the light. This light will then illuminate every time power passes down the brown black wire to the fan motor- is whenever the fan is in operation whether it is switched by the otter or the bypass switch.
Finally I installed the warning light and bypass switch under the dash.and tested operation. I still need to tidy away the wires but the circuits are operating as expected.
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| Bypass switch and warning light installed in mini panel beneath the dashboard. |
Hi, when I first got mine the fan fail light came on while driving. All sorts of expensive assumptions went through my head, got home and checked fuse box, no fuse! never trust the previous owner. Check everything. My car was owned by the previous owner from 1984 until I bought it a few months ago. I have now taken it off the road to check and or replace everything possible,
ReplyDeleteJohn