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What A/C Component Activates Engine Cooling Fan

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
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June
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Re: What A/C Component Activates Engine Cooling Fan

Post by June »

wanderdüne wrote: Fri Jun 15, 2018 8:09 pm Thanks all,
The cabin temp I referred to is the one from the CCM itself behind the tiny grill on the face of the unit. Not really sure how that effects things. I rented a manifold gauges today and it is reading a really high pressure on the high side ~350-400psi and pretty normal pressure on the low side ~45psi @85*F in my garage. Based on the sheet that came with the gauges unit, it looks like it may be the expansion valve is clogged. Going to take it in in the morning to the Tunex by me to get it evacuated and see how much they want to replace that and the receiver drier.

Looks like the least expensive option for me on the temp reading front would be to replace the CCM temp sensor (the xemodex CCM unit is over $500 USD, I think), but I think that it needs to be programmed to the car afterwards. Anyone know if Vida Dice can do that?
Do these cars have expansion valve or fixed orifice? At any rate if either was bad/blocked the low side would read really low according to my husband. Clogged fins from bugs/dirt will cause the high side to run high. Mike says inspect the condenser for debris. He said spray water on the condenser and watch the high pressure reading. If it comes down and the ac temperature is cold than clean the coils with appropriate cleaner, pressure washing it off than recheck. Also if the airflow from fan is not pulling through the condenser properly also will cause high pressure reading. June
My Volvo cars owned
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Re: What A/C Component Activates Engine Cooling Fan

Post by ggleavitt »

k, so maybe the last of my foolish assumptions- Interior temp thermistor not blocked by any crap, and the little fan behind it is working? Fan is PN 8691666 I think, does not include the thermistor. Think maybe you have 2 problems as was noted earlier, the interior temperature sensor difference may or may not be involved with your AC issue.

Link https://www.volvoforums.org.uk/showthread.php?t=122093 for some info on interior temp sensor, include a teardown for replacing the thermistor itself. Another area to consider (and maybe omit)? No idea on the CCM and programming, number of links suggest it's not required. Need VIDA to calibrate dampers I think. Probably ought to get a working VIDA/DICE up if you're going to keep this car regardless, it'll pay for itself in very short time.
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Re: What A/C Component Activates Engine Cooling Fan

Post by wanderdüne »

I did clean the condenser this morning, at least preliminarily. I am going to have my wife drive it to the shop this a.m. and I will track the pressures/temps on my scanner. Thanks ggleavitt for the link on the thermistor. I don't know if the fan is operating behind it. Looks like I can probably find a thermistor wire somewhere online. I probably will bite the bullet and buy a Vida Dice soon. Hard to do when facing unknown bills for this ac work. We will have Volvos for the foreseeable future, though, so it is a good call.
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Re: What A/C Component Activates Engine Cooling Fan

Post by wanderdüne »

Thanks June,
Your husband was right. Driving to the shop, the pressure was reduced by ~80psi on the high side. Cleaning the condenser did have a measurable effect. At the shop, it turned out that the system was overfilled by about 1/2lb of refrigerant. They vacuumed the system and refilled to the proper amount and now the a/c operates as it should. Evap temps are~38*F-41*F.

The high fan speed is not happening now, so it would appear that high system pressure can activate the cooling fan on it's highest speed, which is really loud. That is what has happened here.

I will post up when I replace the thermistor and possibly the fan behind it.

*edit* Also wanted to give a shout out to Eric the Car Guy for his video on cleaning the exterior of the condenser and for his caveat, which I will heed in the future:
"...work that's not necessarily for the DIY. Namely because of the specialized equipment that's often involved and the experience, and the complexity of the system and how it works in general. It takes quite a bit to work on A/C."

Thanks to everyone for your comments and help; thanks MVS.
Last edited by wanderdüne on Sun Jun 17, 2018 7:12 am, edited 1 time in total.
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June
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Re: What A/C Component Activates Engine Cooling Fan

Post by June »

wanderdüne wrote: Sat Jun 16, 2018 2:51 pm Thanks June,
Your husband was right. Driving to the shop, the pressure was reduced by ~80psi on the high side. Cleaning the condenser did have a measurable effect. At the shop, it turned out that the system was overfilled by about 1/2lb of refrigerant. They vacuumed the system and refilled to the proper amount and now the a/c operates as it should. Evap temps are~38*F-41*F.

The high fan speed is not happening now, so it would appear that high system pressure can activate the cooling fan on it's highest speed, which is really loud. That is what has happened here.

I will post up when I replace the thermistor and possibly the fan behind it.

Thanks to everyone for your comments and help; thanks MVS.
Your welcome. Mike said your problem could not be electronic because of the pressure readings you had. He says at certain high and low pressure the computer is supposed to cut the compressor off this is normal. Also when the high pressure hits a certain number the fan kicks to high to move air across the condenser to lower the high pressure. He said on a real hot day especially if recirculate is not selected and interior fan is on a higher setting the high pressure side should kick the radiator fan on high sitting still. That is normal. He said refrigerant pressure also will be higher on a humid day at 90° outside than a dry 90°day. He also said a 134 system is very sensitive to overcharge evaporator temp wise, where as slightly less of a charge will result in slightly cooler evaporator temperatures. That doesn't make sense to me, but it's what he said. Glad your car is fixed! June
My Volvo cars owned
1989 740 GLT ordered
1994 850 4door standard shift ordered
1996 960 ordered
1998 S90 ordered totalled after 3 weeks
1998 V70 GT dealer stock car
2002 S80 T6 ordered totalled
2004 S80 T6 dealer stock car and current car owned
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Re: What A/C Component Activates Engine Cooling Fan

Post by abscate »

I need a hot climate where June is, you want to undercharge the fill by a bit, like 10%, to get best cooling performance. In the temperate North, we overcharge a bit to keep from freezing our EVAps.

If you need to replace a component without pressure loss, you can vacuum and pump on it for a hour and not replace the drier...that’s an up sell a good AC tech will discuss with you

Volvo says if the system is open less than 24 hours, drier replacement is not necessary
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Re: What A/C Component Activates Engine Cooling Fan

Post by Fernandomiguel »

Wella cording to all manuals videos and so on

The high pressure valve is the one that controls the cooling fan
to test it, Take the High Pressure valve and short the connector
the fan should come on!
The etc turns the fan also!
I hope that helps!!
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