DMoneyRX-7

iTrader: (2)

So I recently had an A/C line replaced after not having A/C for about a year. Everything was charged and the line was fixed. I got my car back and the A/C is working...occasionally but not working properly.

Issues:
-Rpm's dip in quick bursts about every 4 seconds. Happens in idle and in regular driving
-The compressor is not engaging last time I looked
-Cold air blows sometimes if I'm lucky
-If I could describe the issue that I am hearing it would be like the compressor is trying to engage and turn on but it immediately catches itself and turns off. Almost like the belt is slowing down for a quick .5 seconds

Things to know for diagnosis:
-Yes I searched and know there are several issues this could mean...(Thermoswitch, Low/High Pressure Switch, Fan Switch)...I just didn't find any answers or threads specific to the 4 sec idle "dipping" and my other specifics
-I got a brand new compressor about 2 years ago.
-PFC Sensor check out shows A/C sensor is on when A/C button is "ON"
-Idle and driving is normal when A/C is off
-The issue occurred before I got my new A/C line installed

If you need to know anything else let me know.

garners_69

i recently had the sort of rev hunting after installing my pfc and not properly doing the learning process when first running ,i reset the pfc and properly did the learning process and now it runs sweet, so was the a/c working when u put ur pfc in if not try resetting it cheers jason

ttmott

iTrader: (1)

Have you looked into the known PFC grounding issue with the AC system? There is a modification posted in the PFC section to add a grounding relay that fixes the intermittent on and off and fan switch problem. Also is your EL system working correctly? If not the compressor load will greatly dip the RPM's.
Just a couple of ideas.....

DMoneyRX-7

iTrader: (2)

the reason I rule out PFC grounding issues is that Ive had the PFC on for about 4 years and for 3 years it was worked fine.

mad_7tist

so is the clutch cycling? do the rpms drop everytime the ac clutch engages?

you say the ac is not 100% that could be alot of things from low pressure and frequent cycling to high pressure causing cycling and bogging of the engine.

first thing is to get a set of gauges on the system and see what is going on

DMoneyRX-7

iTrader: (2)

I woke up this morning and went to see if spinning the clutch manually last night or cycling the A/C relay did anything.

The clutch actually engaged this morning and the A/C worked when I was driving. While the A/C worked though the 4 second interval rpm dipping was still occurring. Then it stopped blowing cold.

I parked and looked to see if the A/C clutch was engaging and it was for a brief second then disengaging.

Now the idle drops rather than cuts for brief intervals. This is occurring everytime the clutch engages.

I am unsure if the "short" pulses of rpm drop are occurring when the clutch is engaging because at the time, the clutch wasn't engaging and it was doing this and also it was when I was driving

RENESISFD

iTrader: (13)

I agree you need to get a set of gaugs on the system to see what the pressures are.

Did the shop use R12 or a substitute?
Did they "convert" it to 134a?
Did you take it back to the shop and see what they have to say?
What are the idle speed setting for ac in the PFC?

I think you need to fix the clutch cycling and see if that fixes your engine issues. I am assumeing that you only have the idle drop when you have the ac on.



John

DMoneyRX-7

iTrader: (2)

I just got my car to a shop to get the pressure checked

Car has been converted to R134 about 4 years ago
Idle speed setting doesn't change if I use my PFC. My guy in Houston who did all my single turbo work took this out and we adjust my idle manually. I keep all idle settings at 1000rpm though.

I'm not really having "engine issues." My engine is fine as the idle doesn't "drop" in normal circumstances, only when the A/C is on...and this just started happening this morning. My idle and regular driving rpm's would "quickly drop/short cut" previously.

So there are two separate rpm issues
-Quick 4 second interval idle and running drops
-Slow idle drops in random occurrences

But what I am really trying to fix is the A/C and not my engine so it is the "quick 4 second interval idle running drops" that I'm trying to fix. The slow idle drop isn't anything new.

Because the compressor is actually turning on and I was getting cold air this morning leads me to believe the issue a matter of the compressor being bad.

I'm thinking that the key issue is either...
-Low pressure switch
-Thermoswitch
-Low freon pressure

However, I just had the A/C recharged and pressure tested about 2 weeks ago. Pressure held for 2 days before he gave the car back.

RENESISFD

iTrader: (13)

When the conversion was done and the compressor changed 2 years ago did you use an R12 compressor or a R134a compressor. I have seen both compressors for the fd and the pressures on the back of them are different as well as some of the pressure controling components like the Pressure switch.


John

DMoneyRX-7

iTrader: (2)

I used the right compressor.

It's fixed now though. Took it to a shop and they checked the pressure. Turns out it was very simple. The guy at Maztech over-pressurized the system.

So if anyone has a problem like this...check your pressure and don't trust the people who recently did you A/C.

Thanks for all the help guys. I needed to resolve this quick as I'm about to drive back up to Nashville from Florida on Sunday.