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Ac Problem, frozen matrix?


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A problem came to light driving this weekend, same symptoms as a problem I had on 2 of my exiges but not heard of any reports of issues on the evora. I have the Ac on constantly but after a while the fan flow reduces until it's almost non existent. If I turn off the Ac it slowly comes back. On my exiges it was a sensor failure allowing the heater matrix to freeze up. Anyone had this problem on the evora?

Gav 

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Mine also turned off completely on a hot day.Worked again the next day. Second time it also threw a spurious fault that needed to be cleared first.

I believe the engine bay gets quite hot and then the ECU decides to protect the system.

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Sounds similar but on both hot and cold days on a long run if I switch the Ac off the flow comes back in minutes so if it was the same as yours I would have thought the engine bay would have to cool down first before it came back on? I've not had any spanner light come on.

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My Launch Edition has evaporator freezing a few times. It normally happens when the AC is on full cold/blower is on 3 or 4 and the outside air temperature is above 20°C. I have confimred this using my borescope (see link below as I've just about used my attachement quota).

Some have mentioned in other threads that water is backing up the drain pipe from the heater/AC box due to a blocked one way valve, causing the water to freeze, so have had it removed.It's something I'm going to have looked at at the next service, but it could be soemthing else. EDIT: I know the thermistor isn't boken because there would be an ODB code and the spanner light would be on (the Service Notes quote that "A thermostat, using a thermistor positioned against the outlet side of the evaporator finning, monitors the temperature of the refrigerated air and signals the ECU to regulate refrigerant flow in order
to provide an output air temperature just above that at which ice may form on the evaporator."
)

http://api.viglink.com/api/click?format=go&jsonp=vglnk_147308167063312&key=c6299c9d4f786d2993c68403dbe79d32&libId=isq2rrls01004p4m000DA2scgkdde&loc=http%3A%2F%2Fwww.thelotusforums.com%2Fforums%2Ftopic%2F82702-evora-nigglesfaults%2F%23comment-651674&v=1&out=http%3A%2F%2Fs3.amazonaws.com%2Ftlf%2Ftlf%2Fforums%2Faws_uploads%2Fmonthly_2016_06%2F5759c3a0ba260_Icing1.JPG.573755ea632e5859da4296e6348aa077.JPG&ref=http%3A%2F%2Fwww.thelotusforums.com%2Fforums%2Fattachments%2F%3Fpage%3D1&title=Evora niggles%2Ffaults - Evora Chat - The Lotus Forums&txt=

Edited by EuropaSman
Correcting typos.

Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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  • Gold FFM

I've had this a couple of times on my LE. The first time, the drain pipe mentioned by Mark above was blocked, so the when the ice melted, it would build up in the heater box, and spill into the footwells.

I'm pretty sure that Matt from Lotus Silverstone told me that the bit in the service notes about a thermistor was an error, and that they were removing that section. He said there is nothing in the system to check for freezing, and that the system relies on hopefully being set up such that the freezing is unlikely when everything is running right. (I hope I'm not mixing that story up with something else).

When this happens, I've found that switching off the A/C, and turning up the heat to full clears the ice quite quickly, then when I turn the A/C back on, I try not to have the temperature on full cold.

My car is going to Lotus Silverstone on Wednesday for another look at my A/C system as it's throwing a fault code related to the compressor speed sensor. 

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No problem Gav. Here's the excerpt from Page 52 of Section EMR in the Service Notes:-

A/C Evaporator temperature sensor

P0537 A/C Evaporator temperature sensor circuit low
P0538 A/C Evaporator temperature sensor circuit high

Description

The A/C system incorporates an evaporator temperature sensor for system control. This is a thermistor device
that changes resistance with temperature. As the evaporator temperature decreases the thermistor resistance
value increases, and conversely as the evaporator temperature increases so the thermistor resistance value
decreases.

Sensor connections               Sensor Connector Description         ECU Pin             ECU Connector
1                                            Sensor signal                                   A3                      48 Way (Right)
1                                            Sensor ground                                 K3                      48 Way (Right)

Monitor:
• Continuous

Enable Criteria:
• Vehicle Running

Disable Criteria:
• None

Malfunction Criteria:
• P0537 – Signal voltage < 0.049V for 1.5 seconds
• P0538 – Signal voltage > 4.399V for 1.5 seconds

Potential failure modes:
• Thermistor wiring open circuit or shorted
• Thermistor fault

Diagnostic Mask:
• The service light will be illuminated for 30 seconds after engine start if the fault has been present for the
previous two trips.
 

Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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  • 2 weeks later...

I've a different problem on ac. After some second at whatever fan speed and temperature, the fab speed reducing and start to go low and fast completely in autonomy... like if you play with fan speed regulation passing from high to low. The dealer order a new circuit mask (under the three climate potentiometers) and I hope that the can solve problems. 

I will update you as soon as they replace it.

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Mine does a similar thing and I've also done the drain pipe mod and removed the two end pieces. I find that on mid to 3/4, after a period of time, the fan starts to slow down and eventually no cold air comes through vents. If I turn fan to max then I can hear the fan but very little air comes through vents. If I switched the aircon off for a couple of minutes, the air comes through pretty quickly, I turn my fan speed down and switch aircon back on again. It must be something freezing up somewhere.

Call it a quirk rather than a fault!

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48 minutes ago, superdavelotus said:

Mine does a similar thing and I've also done the drain pipe mod and removed the two end pieces. I find that on mid to 3/4, after a period of time, the fan starts to slow down and eventually no cold air comes through vents. If I turn fan to max then I can hear the fan but very little air comes through vents. If I switched the aircon off for a couple of minutes, the air comes through pretty quickly, I turn my fan speed down and switch aircon back on again. It must be something freezing up somewhere.

Call it a quirk rather than a fault!

Now have you completely solved it? Or still continue to have crazy behaviour? Do you suggest me to make additionally to what suggested from my dealer?

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  • 2 weeks later...
On 26/09/2016 at 15:20, 21gg said:

Well it's not the drain pipes.

Gav 

That's a shame. Mine goes into Lotus Silverstone for its annual service on Friday and the evaporator icing problem was going to be looked at. It's begining to sound like it's a feature/quirk (a case of TADTS?).

Looking at the airflow diagram I wonder if anything can be done beyond the drain pipe SB and removal of the two one way valves? Could the ECU software be tweaked by Lotus to better regulate refrigerant flow to prevent the air temperature getting too low? I know that there is now a modified HVAC housing but it probably wouldn't make a difference; the parts list states "the D level assembly is wider than previous levels fitted at SOP. If replacing an assembly prior to 10MY vin AH_10901 also change the RH steering rack mounting bracket with the lastest level bracket see 32.03."

 

HVAC.jpg

Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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My first exige 54 plate, had needed the sensor on the matrix relocating, it was actually a bulitin in the USA.

My 07 had the same issues but it was something different and for the life of me I can't remember what it was.

Neither of my previous evoras did this.

Good luck and let us know how you get on.

Cheers Gav 

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Here's an update after the service last week. The air conditioning system was serviced and the refrigerant level was found to be low (down by about 0.2kg), which could have contributed to the evaporator freezing as the refrigreant is having to work harder. It was topped up to a revised level according to the Tech. The original refirgerant figure given in the Service Notes is 0.625 kg of R134a, but I don't know what the new figure is I'm afraid.

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Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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  • 2 weeks later...

That's interesting to know Gav. Fingers crossed that the issue has been sorted now that both our Evoras have been regassed. Mine is coming off the road for the winter at the end of the month. I'll keep an on the aircon in the Spring.

Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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