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david craig
david craig,
Category: Mercury
Satisfied Customers: 888
Experience:  owner/mechanic at 3D Automotive
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2007 mercury montego. We replaced the compressor, condenser,

Customer Question

2007 mercury montego. We replaced the compressor, condenser, expansion valve and all related parts. It doesn't cool as well as it should and at highway speeds the compressor kicks in and out repeatedly. It has the recommended amount of R134 in the system. It is a scroll compressor and the pressures look good
Submitted: 2 months ago.
Category: Mercury
Expert:  Ron replied 2 months ago.

Hello. My name is ***** ***** I am happy to assist you today. Give me just a moment to review your post, and I'll be right back with the help you need.

Expert:  Ron replied 2 months ago.

Can you give me your pressure reading, need the low and high side readings with the AC running please.

Customer: replied 2 months ago.
Low 50 high 200 to 230
Customer: replied 2 months ago.
This is at idle
Expert:  Ron replied 2 months ago.

Normal pressure on this system should be right at 35 to 40 PSI on the low side and 200 to 210 PSI on the high side, are you sure you not over charged? Your pressures are on the high side.

Customer: replied 2 months ago.
Don't think so. Underwood sicker calls for 1lb 13oz and we used our snap on machine to add it. Vent temp is around 55 degrees at idle and warmer on the road. Everything I have found on these systems is opposite to what we have
Expert:  Ron replied 2 months ago.

If you run some water over the condenser dose the temp come down any ?

Customer: replied 2 months ago.
Haven't done that. Car is not here at the moment
Expert:  Ron replied 2 months ago.

Let try that when you get a chance and also try clamping of the heater hoses to stop the flow of coolant through the core and let see if the temp will change, post back with the results and we can work from there.

Customer: replied 2 months ago.
What are ur thoughts on the cycling at highway engine speeds? It's like one that is low on refrigerant would act.
Expert:  Ron replied 2 months ago.

It would seem like a pressure issue unless the evaperator is trying to freeze up, have you scanned the system to see if there are any fault codes setting?

Customer: replied 2 months ago.
No fault codes
Expert:  Ron replied 2 months ago.

With all the parts you replace this thing should be blowing cold as ice.

Expert:  Ron replied 2 months ago.

One other thing that comes to mind that there are known issue with could be a failing evaporator discharge air temperature sensor .

Customer: replied 2 months ago.
Exactly. If not for the cycling issue I would be looking at an issue inside the dash or the controller.
Expert:  Ron replied 2 months ago.

Have you had a look at the evaporator discharge air temperature sensor , there are known issues with it sending a fault reading from the evaporator which can cause the compressor to cycle.

Customer: replied 2 months ago.
The car will be back here at 1. Where is the evaporated sensor located?
Customer: replied 2 months ago.
When the compressor cycles.the pressure swings from app. 50 down to 30 and the clutch kicks out and it starts going back and forth with the compressor being engaged noore than 2 to 3 seconds before it kicks out
Expert:  Ron replied 2 months ago.

Okay let check the Evap sensor and see if it checks okay, theirs not much left providing none of the new parts are defective which is very doubtful.

Customer: replied 2 months ago.
Still having issues with the AC on the 07 montego. We replaced the sensor at the evaporator core and it made no difference.
Expert:  Ron replied 2 months ago.

Did you try blocking the heater hoses off?

Customer: replied 2 months ago.
we did. No difference
Expert:  Ron replied 2 months ago.

Okay the complete system is new and the only thing that looks odd to me is the pressure readings , they seem on the high side. Unfortunately I am out of ideas. If you would like, I can open the post back up for you and perhaps someone else may have something new to add.

Customer: replied 2 months ago.
Please do. We are out of ideas as well
Expert:  Ron replied 2 months ago.

Okay, doing so now.

Expert:  david craig replied 2 months ago.

Hi Im David, just throwing my 2 cents in. With the manifold gauge set hooked up and the ac running what are the high side and low side cylcling at ?

Customer: replied 2 months ago.
The low side is running about 40 to 50 psi and the high is around 230-240 at idle. When u run it at 2000ish rpm the high side stays pretty steady and the low drops to about 30 and then starts cycling on and off rapidly
Expert:  david craig replied 2 months ago.

ok, 30 is a bit high but not bad. hide side is a problem. it should cycle

Customer: replied 2 months ago.
We've got the exact amount of R134 called for in the car. Starring to consider some type of restriction on the low side
Expert:  david craig replied 2 months ago.

when you evacuated the system before replacing all of the components, did you pull vacuum for at least 30 minutes?

Customer: replied 2 months ago.
20 min evacuation and 10 min leak test
Expert:  david craig replied 2 months ago.

ok. statically right now. vehicle off. manifold gauge hooked up, what are your readings.

Expert:  david craig replied 2 months ago.

any update?

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