A/C, RPM Issues.

[239]

I have a 2000 xlt that has RPM trouble whenever I turn on the A/C or Max A/C. I've noticed that when I turn the A/C on the RPM rises on it's own, goes back down, then makes a "clicking" sound and rises again. This process happens about 6-8 times a minute. Does anyone have an idea of what this might be? I would greatly appreciate any info on this. Thanks in advance.

 

[2000StreetRod]

low refrigerant pressure?

The PCM increases the engine idle speed when the A/C compressor clutch is engaged. If the refrigerant low pressure sensor determines the pressure is too low then the compressor is disengaged. With the engine idling and the A/C on see if the compressor clutch is cycling betweeen engaged and disengaged. If so, then you should check your refrigerant pressure and charge if low. If not low, then your low pressure switch needs to be checked and possibly replaced.

 

[hansvdweerd]

The PCM increases the engine idle speed when the A/C compressor clutch is engaged. If the refrigerant low pressure sensor determines the pressure is too low then the compressor is disengaged. With the engine idling and the A/C on see if the compressor clutch is cycling betweeen engaged and disengaged. If so, then you should check your refrigerant pressure and charge if low. If not low, then your low pressure switch needs to be checked and possibly replaced.

Do I understand correctly that the 'click' the OP mentioned is the A/C compressor engaging and disengaging? And that this compressor shouldn't engage en disengage while the A/C is on?

My reason for asking is that I recognize this 'click' in my own Explorer (but much less frequent).

 

[my98nnj]

The A/C compressor does indeed cycle to maintain the correct line pressures/temp.
6 - 8 times per minute is a short cycle and might point to a low R134 condition.

 

[hansvdweerd]

The A/C compressor does indeed cycle to maintain the correct line pressures/temp.
6 - 8 times per minute is a short cycle and might point to a low R134 condition.

Thanks! I'll check if the cycle on my Ex is short like this one or (more probably) longer. The A/C does give a good cold breeze.

 

[239]

I forgot to mention that my A/C puts out cool air, not exactly cold. And it also has a strange smell when it's switched on, the smell is gone about 20 seconds after I turn it on though.

 

[italianbigsky]

I had the same problem with my mazda some years ago. AC was on and cold as ice, but I heard the "clic" many times per minute. The problem was the electric cable. It was too short and while engine idle, or during acceleration, it simply moved and lose contact, so that it was just like turning AC off.
I hope you can understand my poor english! No matter if this post isn't helpful in your sitution, I tried to explain the best way!

 

[239]

The PCM increases the engine idle speed when the A/C compressor clutch is engaged. If the refrigerant low pressure sensor determines the pressure is too low then the compressor is disengaged. With the engine idling and the A/C on see if the compressor clutch is cycling betweeen engaged and disengaged. If so, then you should check your refrigerant pressure and charge if low. If not low, then your low pressure switch needs to be checked and possibly replaced.

Yes, when it's in idle it seems to be worse. It engages, disengages.

 

[goalkeeper21986]

Same problem? Did you fix it?

Before I posted my own problem I did a search and what do you know...someone else already posted it.

Here's a video of what is going on, is it the same problem as yours? If so, did you fix it and how?

http://www.youtube.com/watch?v=SQZ8KCaD5Y0

 

[ranger7ltr]

That video doesn't really show a problem...

Before I posted my own problem I did a search and what do you know...someone else already posted it.

Here's a video of what is going on, is it the same problem as yours? If so, did you fix it and how?

http://www.youtube.com/watch?v=SQZ8KCaD5Y0

It shows that the Ford PCM compensates for the load of the engaging of the a/c compressor clutch by raising the idle rpm... The system is cycling on, with the click and the rise in rpm, then clutch off by the drop in idle rpm...

The cycle time MIGHT indicate a marginal to low refrigerant charge but this is normal behavior on the clutch click and rpm rise...In any case I would use a proper set of gauges and test the charge level and correct it before trying to "correct" the idle rpm rise... The faster the system cycles the lower the charge level is and to cool properly the charge level needs to be increased and any leaks fixed before recharging...

Normal vent temps I see in the heat of the day are still 36-42F center vent...

That or don't turn on the a/c...

 

[goalkeeper21986]

@ranger7ltr Thanks for such a quick and thorough reply! I was already thinking I need to recharge the AC, its been 5 years I think. I'll post another reply with the results.

 

[Kenneth J]

So where is this low pressure sensor located? I just installed a new compressor, had the system leak checked and charged. Its cooling but not as good as for example my Volkswagen. Also my idle rpm drops dramatically every 8-10 seconds when the compressor is clicking on and off.

 

[goalkeeper21986]

AC Recharge did the trick, and as a bonus my AC is ice cold!

To be more specific, the AC compressor does not cycle on and off anymore when idling, Thanks!

It shows that the Ford PCM compensates for the load of the engaging of the a/c compressor clutch by raising the idle rpm... The system is cycling on, with the click and the rise in rpm, then clutch off by the drop in idle rpm...

The cycle time MIGHT indicate a marginal to low refrigerant charge but this is normal behavior on the clutch click and rpm rise...In any case I would use a proper set of gauges and test the charge level and correct it before trying to "correct" the idle rpm rise... The faster the system cycles the lower the charge level is and to cool properly the charge level needs to be increased and any leaks fixed before recharging...

Normal vent temps I see in the heat of the day are still 36-42F center vent...

That or don't turn on the a/c...

 

[steve101]

sry to bump old thread:

same issue as op but little bit different my compressor used to click on and off, now it doesn't instead bogs down the engine to 500 sometimes 400 and kills a lot of amps. i cant not figure this out.