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Another head scratcher? UPDATED!!! Pages: 12Last

badufay on Thu September 27, 2007 5:48 PM User is offline

Year: 1998
Make: VW
Model: Golf
Engine Size: 2.0
Refrigerant Type: R-134A
Ambient Temp: 85
Pressure Low: 30
Pressure High: 250

I have another issue that doesn't seem to make much since after reading a lot of these posts. On my Golf, my vent temp sits around 45 F now while my car is at idle (85 - 90 F outside). Both speeds on the electric radiator fan are working just fine, the condenser seems to have a good temp drop (the top hose is very hot, where as the bottom hose is just warm). The problem is, when i start driving the car at highway speeds, the vent temp actually increases to about 50 F. Recirc air is one and working, it just seems weird because everything I have read says it should actually be the opposite. Any Ideas?

Thanks,
Ben

Edited: Tue October 02, 2007 at 8:08 AM by badufay

Dougflas on Thu September 27, 2007 6:00 PM User is offline

Possible slightly low in charge. If you have a low charge, at higher RPM the system will get satisfied and stop cooling so the coil won't freeze up.

badufay on Thu September 27, 2007 7:35 PM User is offline

the system was charged about 2 weeks ago, and has no leaks. actually because of other issues the system was evacuated and then recharged, with no r-134a lost (had to add 2 more oz of oil). the car is charged with about 28 oz and 4 oz of oil.
Ben

2POINTautO on Fri September 28, 2007 1:34 AM User is offlineView users profile

Just a little info here, the two lines at the condensor should not be more than about 50 degrees F from the hot inlet to the not as hot outlet, more than about 50 degree drop shows a restriction in the condensor. Going faster and the vent temps getting warmer is also a sign of being overcharged so you need to drive with the pressure guages hooked up and mounted where you can monitor them while driving and let us know what the pressures are at cruising speed, that will tell the whole story. Also is the HI side pressure fitting before or after the condensor please.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

badufay on Fri September 28, 2007 9:32 AM User is offline

OK, I will try and get the pressure readings while driving today. My high side fitting is after the condenser, it is right before the expansion valve and evaporator. Could air in the system do the same thing as well?

Ben

badufay on Fri September 28, 2007 6:16 PM User is offline

Ok, i did a little more work on it today. I completely evacuated the system, then held a vacuum for 30 min. recharged with straight 134a (28 oz). At idle the pressure is 30 L, and 215 H @ 90 F. The vent temp now gets down to a nice cool 40 F. However, still while i drive at highway speed, the vent temp jumps up to 50 F (recirc air is on). Any ideas now since I know the charge is correct?

Thanks,
Ben

Dougflas on Fri September 28, 2007 11:15 PM User is offline

The system uses a switch that is activated by the temp of the evaporator. If the temp of the evap gets to 32º, the switch will open and interupt the 12volts to the clutch. Make sure the sensing capillary tube of the switch is in place and the switch is functioning.

badufay on Fri September 28, 2007 11:36 PM User is offline

Dougflas, thank you for the reply, but looking over pictures, and wire diagrams, that piece does not exist on my system. However, just to rule out any compressor cycling on and off, I will jump it tomorrow and take it for a quick drive. If it stays cold, then I will know it is something in the electrical circuit, but i don't think the compressor is kicking on and off, I can usually feel this, and rear the relays. Any other ideas?

Ben

2POINTautO on Sat September 29, 2007 4:02 AM User is offlineView users profile

The pressures will tell the story, are you just unable to get them while driving, since the HI side fitting is after the condensor then we will not see a clogged condensor but we will see how hot the HI side is getting while your vent temps go up. No sign of a thermistor in the evap case, that is strange, what is going to turn off the comp in case of freezing, either way, I do not think this is your problem anyways, it would get cold again.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

Dougflas on Sat September 29, 2007 8:26 AM User is offline

My schematic definitely shows that switch. It is connected in series with the ambient temp cutout switch. This switch I mentioned previously is located in the center of the engine compartment; it has a green lead on one side, and white/yellow wire on the the other side. The name of the switch is "AC thermal cutout switch".

Dougflas on Sat September 29, 2007 8:39 AM User is offline

Ben and 2 point,

This is a non-cycling system meaning the clutch in normal operation does not cycle on and off. It most likely uses a TXV (I did not look that up) that will normally control the flow of refrigerant. The thermal cutout switch is there for the sole purpose of preventing evap freeze up. If this switch does not open when the evap senses 32º, the evap will stay frozen. Do you feel a reduction of airflow thru the ducts?

badufay on Sat September 29, 2007 8:58 AM User is offline

I will try to get the pressures, but I need to come up with a way to rig the gauges. I am looking at the VW service manual right now the thermal control switch that you are referring to only detects coolant temps. Yes, it does turn on and off the compressor, but only based on coolant temps. On the VR6 models, it also turns on and off the third seed for the radiator fan. In answer to the other question, i can't really tell any difference in air flow when the temps warm up, so i don't think the evaporator is icing up (plus the vent temps have never gotten below 40, i would assume they would get close to 32 before climbing up again).

Thanks,
Ben

Edited: Sat September 29, 2007 at 9:00 AM by badufay

Dougflas on Sat September 29, 2007 9:30 AM User is offline

Send me a fax number and I'll fax you the info. Either the manual you're looking at or the one I'm looking at is in error.

[email protected]

badufay on Sat September 29, 2007 9:45 AM User is offline

i don't have a fax available right now, but i have done a little more research, it seems VW only installed the evaporator temp control switch on the cars with auto temp climate control. I am going to go and jump the compressor and take it for a quick highway drive. Also hopefully rig up the gauges so i can see the pressures while driving and when it gets warm. I appreciate your quick responses, I will post the results in about an hour or 2.
Thanks,
Ben

badufay on Sat September 29, 2007 9:49 AM User is offline

I think this is the part you are thinking of... http://www.worldimpex.com/parts/genuine-part-ac-temp-switch_168830.html . I am going out to my car right now, to do those things I said. I will get back to you.
Ben

badufay on Sat September 29, 2007 1:46 PM User is offline

ok, so i jumped the compressor, and everything worked at idle, vent temp sat around 43 F at idle. when i got on the highway, it increased to about 48 F. I am not going to be able to drive with the gauges hooked up unless i completely remove the hood. Any ideas?

Thanks,
Ben

2POINTautO on Sat September 29, 2007 1:57 PM User is offlineView users profile

Put the gauges out of the hood with the hood ajar, use some rope or a bungie cord to add some safety to keep it from flying open while driving down the road, if the HI pressure goes up over 250 then you have an air flow problem through the radiator condensor or you are overserviced, even a little too much makes a big difference, we need those pressures man.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

TRB on Sat September 29, 2007 2:14 PM User is offlineView users profile

Air flow or control valve is areas I would check. Were these not Sanden knock off compressors you posted about in the other expansion valve thread. Maybe that was a different poster. I can't remember I'm getting old like Chick.

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badufay on Sat September 29, 2007 6:30 PM User is offline

I will attempt to rig the gauges again, i get what you are saying. The compressor was a rebuilt one that I was refering to in the expansion valve question. Today while i was out, i actually looked forward to stop and go traffic. with the vent on low/medium the vent temp was about 38 F, but like before, once i started driving the temp raised to about 50 F (even when i kept the rpm's low or in neutral). When i rev the engine with the gauges hooked up, the high pressure really doesn't change much, but the low drops to about 27 or so before stabilizing back around 30.
Ben

Dougflas on Sat September 29, 2007 10:53 PM User is offline

Didn't realize you had a variable displacement compressor. But if you had an airflow problem, the problem should be at idle as there would not be enough air crossing the condenser. At high speeds, the vehicle is moving so you'd have more airflow across the condenser, right? When you rev the engine, the low side drops to 27 as you stated but goes back to 30psi. That is 34º. THAT is the reason why I keep looking at the dang thermal cutout switch that keeps the evap above freezing. If the evap freezes, air will not blow thru it transferring the heat from the air to the refrigerant.

BTW... the manual sysstem has this switch.




Edited: Sun September 30, 2007 at 12:37 AM by Dougflas

badufay on Sun September 30, 2007 11:06 AM User is offline

Dougflas, thanks again for the reply. The thermal cut-out switch that you are referring to does exist, i show it in all my manuals, and have even replaced one before in the past. However, that switch sits inside a coolant/antifreeze hose and open and closes at a specific coolant/antifreeze temp. It sits inside the center of the engine compartment right off the cylinder head flange (here is that part... http://www.autohausaz.com/search/product.aspx?sid=0bhrokvnotpazjj0yuj1priw&[email protected]&[email protected]%20&year=1998&[email protected]%20%26%20Heat%20-%20Climate%20Control&[email protected]%20Cutoff%20Switch ). I am going to go rig up those gauges right now and try to post some pressure readings.
Thanks again for everyone's help.
Ben

Dougflas on Sun September 30, 2007 12:22 PM User is offline

I still think we're talking about a different switch.





Edited: Sun September 30, 2007 at 12:59 PM by Dougflas

2POINTautO on Sun September 30, 2007 1:13 PM User is offlineView users profile

Yes, Part #10 is the thermistor, but I still do not believe that it is the problem with this car. This is the part that keeps the evap from freezing over and lowering vent air flow (volumn), I do not believe that this thread is about this type of problem.

I am still debating an overservice, bad TXV or bad variable displacement compressor.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

badufay on Sun September 30, 2007 1:30 PM User is offline

Well, it's not overcharged, I know that for a fact, just vacuumed it out for 30 min, and then recharged withThe TXV is brand new (actually replaced it twice because thats what i thought the first time, so i tried a new one). I am pretty sure the compressor is SH**. I got the gauges hooked up this morning, Outside air was about 85. Turned a/c on, recirc air as well, vent temp dropped down to 40. L= 32, H=210. Everything here looks great!!! But!!! When i start driving the high side goes down to 150, then down to about 135. The low side stayed around 33-34, and the vent temp creeped up to about 46-48. After returning home, I let it idle in the garage, and after about 5-10 minutes the high side went back up to about 175. This sounds to me the compresor is just junk and just can't keep up.

Ben

2POINTautO on Sun September 30, 2007 2:49 PM User is offlineView users profile

I VOTE COMPRESSOR, thanks for PMS, putting up with my Shite.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

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