Air Con: 70: - '98 S70 Bizarre A/C Issue ;-0 - Page 2

Chris_Rogers · Jan 14th, 2008, 19:36

A thought, are you running the fan on 'AUTO' when the system stops working?
If so, have you tried running the fan on a manual setting? does the same fault occur?

M Miller · Jan 14th, 2008, 19:54

Hi guys;

A number of recent questions have popped up in this thread so let's address as many as I can

Cabin temperature sensor - I haven't checked them but I did put an evaporator in this car and didn't see any obvious issues. I was aware at the time what the sensors were and was careful to re-connect them etc.

The settings on the control head are all set to manual for testing - the idea is to get around ECC control as much as possible.

I have thought about WOT - I realize the system will cut out at WOT. The system will operate properly in the shop at idle and also if you run the engine at 2,000 RPM while stationary.

I've been thinking about running a wire from the compressor into the interior of the vehicle to check for power to the compressor while driving - I'm dead certain we'll find it's not being told to turn on - but it would be worth a 100% conclusive answer.

Engineer · Jan 14th, 2008, 20:57

You really should check for any fault codes as some will continue to give poor performance if not cancelled despite the fault being cured, however failing that you could also check out the coolant temperature sensor as if this is faulty and reads to high it will trigger an AC shut down as will exhaust temperature if too high (the ECU works out the exhaust temperature based on RPM, MAF and throttle position readings) something you won’t get in the workshop when not under load. Road speed is also considered by the ECU so don't discount the speedo. I am assuming this is a 4.4 Bosch control system although the ME7 is similar but also uses MAP sensors as well as a MAF.

Cheers

ShadeTek · Jan 14th, 2008, 23:17

Also, does the radiator fan come on when the AC is switched on? I believe this is supposed to happen.

M Miller · Jan 14th, 2008, 23:26

Engineer: I agree with your post however, we don't have a Volvo scan tool. Either way, we'll get into the midst of your post more/less as a last resort after everything else is taken care of first.

ShadeTek: The radiator fan does come on at some point during the A/C cycle - it is working as it's supposed to.

Jan 14th, 2008, 20:57	#13
Engineer Rubbing son is racing.... Last Online: Jan 18th, 2017 14:26 Join Date: Nov 2004 Location: London	You really should check for any fault codes as some will continue to give poor performance if not cancelled despite the fault being cured, however failing that you could also check out the coolant temperature sensor as if this is faulty and reads to high it will trigger an AC shut down as will exhaust temperature if too high (the ECU works out the exhaust temperature based on RPM, MAF and throttle position readings) something you won’t get in the workshop when not under load. Road speed is also considered by the ECU so don't discount the speedo. I am assuming this is a 4.4 Bosch control system although the ME7 is similar but also uses MAP sensors as well as a MAF. Cheers __________________ Engineer

Jan 14th, 2008, 23:17	#14
ShadeTek Premier Member Last Online: Apr 9th, 2024 19:03 Join Date: Dec 2002 Location: Renfrewshire View Photos By: ShadeTek	Also, does the radiator fan come on when the AC is switched on? I believe this is supposed to happen. __________________ Tek-Emo Villis Emo Bis V70 SE NAV 1.6 D2 2015MY POWERSHIFT, D4162T, 86000miles, RED. /VOL FCR/PEPER OBD2/Acron 9135 OBD2/L.E.D Flasher/VDASH/ANCEL BA301

Jan 14th, 2008, 19:36	#11
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	A thought, are you running the fan on 'AUTO' when the system stops working? If so, have you tried running the fan on a manual setting? does the same fault occur?

Jan 14th, 2008, 19:54	#12
M Miller New Member Last Online: Feb 5th, 2008 03:25 Join Date: Jan 2008 Location: Parksville	Hi guys; A number of recent questions have popped up in this thread so let's address as many as I can Cabin temperature sensor - I haven't checked them but I did put an evaporator in this car and didn't see any obvious issues. I was aware at the time what the sensors were and was careful to re-connect them etc. The settings on the control head are all set to manual for testing - the idea is to get around ECC control as much as possible. I have thought about WOT - I realize the system will cut out at WOT. The system will operate properly in the shop at idle and also if you run the engine at 2,000 RPM while stationary. I've been thinking about running a wire from the compressor into the interior of the vehicle to check for power to the compressor while driving - I'm dead certain we'll find it's not being told to turn on - but it would be worth a 100% conclusive answer.

Jan 14th, 2008, 23:26	#15
M Miller New Member Last Online: Feb 5th, 2008 03:25 Join Date: Jan 2008 Location: Parksville	Engineer: I agree with your post however, we don't have a Volvo scan tool. Either way, we'll get into the midst of your post more/less as a last resort after everything else is taken care of first. ShadeTek: The radiator fan does come on at some point during the A/C cycle - it is working as it's supposed to.

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