| Author | Message | |||
     richard murphy Yet to post message Username: freo90mulsanne Post Number: 1 Registered: 06-2019 |
Aircon works fine when I go out somewhere. So I park it for a while, then when I start it for the return journey there is nothing - no fan or cold air. I leave aircon switched on, and then after about 8 -10 mins of driving it comes on and works fine. This has occurred many times, consistently. What is causing this 10 minute delay, always after it has been used earlier that day ? Thanks, in anticipation | |||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 665 Registered: 11-2017 |
The delay is built in. This is to insure the system is cold for A/C or warmed up for heat. | |||
| Jim Walters Frequent User Username: jim_walters Post Number: 333 Registered: 01-2014 |
There is a delay built in as Rob says that limits the operation of the AC system until the engine coolant temperature has reached 44°C. (Some descriptions are for 45°C) This is to keep you from getting a blast of cool air from the system if you have heat selected when the engine is first started. If the sensor malfunctions, which is quite common, you will get no fans or hot or cold air. It is very possible that the 44° sensor on your car is failing and not working as it should. To test, locate the 44° sensor plug on the thermostat housing and pull it off. The AC should then work all the time, right from cold and also when the engine has fully warmed up. If there is no difference with the sensor plug pulled off then something else is not functioning properly. Try that test first and report back. The diagram below may pertain to your car depending on model year.  SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | |||
| Frans Koek Yet to post message Username: frans_koek Post Number: 1 Registered: 07-2013 |
Richard, I had a very similar problem with my ‘89 Turbo RL. I checked all relays, contacts and disconnected the switch as described by Jim. That didn’t solve the problem. The various relays related to the aircon/fan system are switched by way of an earth to pin 85 (from memory) coming from the circuit board that lives in the middle console. All pins 86 should have a positive feed as soon as you start the engine. Remove the relays and check that you have a positive feed to the pins 86 sockets with engine running. Switch aircon/fans on and check that you get an earth connection to pins 85. In my case the problem was no earth connection to the pins 85 sockets and therefor the relays wouldn’t switch the aircon and fans. Eventually a replacement circuit board solved my issue. These boards are know to cause problems with age. FS sells reconditioned boards. Good luck, Frans | |||
| richard murphy New User Username: freo90mulsanne Post Number: 2 Registered: 06-2019 |
Thank you so much, Frans. Now I do not even know the name of this assembly of parts, but mine appears to be slightly different to your diagram. (my offsider is a handy mechanic, but away at the moment). (Bentley Mulsanne S 1990 # 32658) That top pipe out (in?) has the number "70148" on it, and it is obviously different. hopefully you can see attached photo. Thx again
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| Jim Walters Frequent User Username: jim_walters Post Number: 335 Registered: 01-2014 |
Thermostat housing. Illustration for your VIN:  Pull off all two wire connectors to test. If no change in operation check relays as mentioned by Frans. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | |||
| Darryl Watson Experienced User Username: inox Post Number: 146 Registered: 04-2015 |
I don't know if it's any help to you I had our control PCB repaired a number of years ago by Bowling Engineering in Leeds (UK). Details below. The price at the time was competitive. A B-RR modification was to fit a removable plastic membrane (sheet) over the top of the PCB. Details: BOWLING ENGINEERING LTD • Great BritainUNIT 5, FISHBROOK IND EST, • STONECLOUGH ROAD, • KEARSLEY BOLTON, • LANCASHIRE • BL4 8EL Phone: +44 (0) 1204 862500 fax Fax: +44 (0) 1606 48448 John Bowling johnrr@btconnect.com |
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