| Author | Message | ||
     Mark Tennison New User Username: fixstuff Post Number: 26 Registered: 11-2020 |
1977-1980 Corniche DHC. So I thought a nice easy fix, the Aux/Booster/coolant fan runs as soon as ignition is turned on with engine cold, this does not seem correct to me, I would have thought the fan should only run when the engine coolant temp is above norm. ? I was measuring the switch pins(the one hard to see in pics as it is underneath the thermostat outlet) to confirm the terminals were short/normally closed when the internals of the switch fell out of its housing (The retaining "O"ring had perished) ! although unexpected this gave me the opportunity to check the function of the switch & get numbers off it JLY79 B44G or B446..it works correctly but in my mind the wrong way around for correct fan functionality! So what's going on a) am I wrong in my assumption that the fan should not run when the engine is cold, b) Back in time could the wrong switch have been fitted or c) the wrong connector (there are 3 that with effort could be fitted to any one of the 3 switches) put on the wrong switch. Conformation of switch type, location, connector, wire colours will be very much appreciated. Hope Pics help   | ||
| Mark Tennison New User Username: fixstuff Post Number: 27 Registered: 11-2020 |
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| Jim Walters Frequent User Username: jim_walters Post Number: 336 Registered: 01-2014 |
Wires are most likely on incorrect sensor (switch). The switch circled in blue is the 44°C AC inhibit switch that prevents heat/ac fans blowing until coolant reaches 44°C. It is an NC switch (Normally Closed). If the fan switch wires and plug are on this switch the aux engine cooling fans operate from cold but will turn off when coolant reaches 44°C. Upper pic on the right is the engine auxiliary cooling fan switch, NO, which turns on radiator fans when coolant reaches about 85°C. This switch often fails to turn on the cooling fans even upon coolant boiling. Swap those two connectors to correct operation. The left switch in the top pic is for the EGR inhibit until engine coolant warms up. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Tennison New User Username: fixstuff Post Number: 28 Registered: 11-2020 |
Jim, Many thanks, I just need to double check wire colours etc... before swapping over the connectors however, I am very confident that sometime in history, maybe when the Thermostat was last changed these 2 connectors got transposed and it may even have been the reason the car was taken off the road and put in to storage, as I am wondering why the cabin heater blower fans are inoperable in all situations could this config have caused this ? I think fans not working is my last fix to do on the shopping list. Be very useful if all this switch/sensor info with Part numbers, specifications and physical locations was all in 1 place.  Many thanks again | ||
| Jim Walters Frequent User Username: jim_walters Post Number: 337 Registered: 01-2014 |
Mark, if the wires and plug for the 44° switch are plugged into the aux fan switch then the blower fans will not work unless the coolant temperature gets very hot. To check for 44° switch failure simply leave it unplugged. If you do that, the ACU fans should function irregardless of coolant temperature. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Mark Tennison New User Username: fixstuff Post Number: 30 Registered: 11-2020 |
Jim, thanks again I feel like I know exactly how to correct this historical connector/switch error however, 1 thing does not stack up... the cable pair routings to the 44°C (NC) and the 105°C (NO) seem like they were factory dressed, to swap them over (correct the error) will mean an unnatural cable routing. Would be very useful to have each connector cable pair color code to which switch info. Cheers Mark FI - The 3rd switch is a 14°C, no concerns with this. The °C values come from the actual Otter switch black plastic cases. | ||
| Omar M. Shams Grand Master Username: omar Post Number: 2121 Registered: 04-2009 |
Maybe the connectors and cables are in the correct physical location but the probes have been moved around in the past. | ||
| Mark Tennison New User Username: fixstuff Post Number: 31 Registered: 11-2020 |
Please check my findings and agree or otherwise. Cheers Mark   |
