Ac problems

[Steven Todorow]

So I’ve had ac problems for about a year now, had the evap replaced and still didnt solve the problem. I have a 05 ford Mustang v6 from America.

So I just got out of the shop today and had the system recharged cause it was a little low and in the past three months might have used it a couple times.

So it blows freezing cold 40 degrees but the compressor keeps turning on and off about every 15-20 secs so on for 15 then off for 15. and I’ve been to 3 shops all say no leak except it’s always a little low when I take it in they all put dye in it and sniff it and find nothing and all charge it to the right pressure. It seems to only do it at idle but unsure.

But today they recharged it and I had it on for 20 mins and I heard the compresser turn on and off every 15 secs, I don’t get how in 20 min it could of lost that much freeon to turn it on off and them not being able to find it.

So I’m thinking it might be a switch, heard those go bad in a lot of them?
I’m just curious if the comprosser is supposed to cycle on and off cause I’ve heard different everywhere, it wasn’t very hot out today maybe 70 and the ac wasn’t on the coldest setting maybe like 75ish so maybe it’s supposed to do that, I’ve read mixed feelings about everything some say it’s not supposed to turn on off and some say it does. Just don’t get how it cycles like that after just being recharged
Thanks for any help

Topic

[Logan Kistler]

I would look up the specs of the high and low pressure switches and figure out when the pump is supposed to be switching on and off. Then hook it up to the machine and see if the pressure changes correlate to when the pump is switching on and off. This may not work depending on where the service ports are located in relation to the switch, but if the high side is close to the switch there shouldn’t be any pressure drop. If you jump the switch to kick the pump on and the system runs normally, with no erradic pressure changes, I’d toss a switch at it.

For the leak, if it is losing freon with no traceable leaks the most likely culprit is probably the evaporator as it is the most hidden component, most the time it doesn’t get checked when looking for leaks, and most of the time it leaks into the hvac airflow and since sniffers go off when they sense airflow it makes it hard to identify. I’ve seen a few slow leaking evaporators come through the shop and if all else is running normally the customers usually elect to do seasonal recharges

[Steven Todorow]

Thank you I will give it a shot

[Larry Bible]

I don’t have anything close at hand, but most basic auto a/c manual will have a chart for Ford systems that will give you a cycle time for the ambient temperature after stabilization. Depending on the ambient, this might be normal. The only way to know for sure is to arm yourself with; the chart, a thermometer and manifold gauges.

Hope this helps.
Doc

[Steven Todorow]

[quote=”MBDiagMan” post=160568]I don’t have anything close at hand, but most basic auto a/c manual will have a chart for Ford systems that will give you a cycle time for the ambient temperature after stabilization. Depending on the ambient, this might be normal. The only way to know for sure is to arm yourself with; the chart, a thermometer and manifold gauges.

Hope this helps.
Doc[/quote]

thanks best advice ive gotten so far

[James O’Hara]

In most cases it will not cycle like that cause it will burn up the clutch. There is a large variety of things that could be causing it. Especially with it being a climate control system instead of the old knob style or even older cable style.

There are normally resistance tables for the temperature/pressure sensors/switches. High Pressure switches tend to go bad on lots of brands. If I listed every possibility you would have a list a mile long. You need to have the software to communicate otherwise is pretty much useless trying to diag it. Only person that will have that is the dealership.

Another thing the is often overlooked is the schrader valves leaking but, you have to have a feel for them as they are extremely easy to break.

[Steven Todorow]

[quote=”MDK22″ post=160719]In most cases it will not cycle like that cause it will burn up the clutch. There is a large variety of things that could be causing it. Especially with it being a climate control system instead of the old knob style or even older cable style.

There are normally resistance tables for the temperature/pressure sensors/switches. High Pressure switches tend to go bad on lots of brands. If I listed every possibility you would have a list a mile long. You need to have the software to communicate otherwise is pretty much useless trying to diag it. Only person that will have that is the dealership.

Another thing the is often overlooked is the schrader valves leaking but, you have to have a feel for them as they are extremely easy to break.[/quote]

yeah i had an appt for ford but canceled it because i checked out my parents car, one a brand new 2014 honda accord with 20k miles on it and it was cycling roughly the same amount and our 2003 chevy Tahoe that never has had a/c problems. so i figured if they where cycling the same amount then why bother going in till i know there is a leak. so i figured id just get the leak detection kit and see from there, just trace over the lines if not maybe it is a switch

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