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gthomas
User
Jul 14, 2009, 8:41 AM
Post #1 of 21
(1874 views)
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I have a 99 Mustang and the Cold air conditioning comes and goes while on. I was told that there is a relay? that isn't functioning properly.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 14, 2009, 8:56 AM
Post #2 of 21
(1871 views)
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What exactly is happening? Is the compressor cycling on and off so frequently that the air doesn't get cold enough or is it going from real cold to off and back on again?
When is this happening? Have you tried anything yet?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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gthomas
User
Jul 14, 2009, 9:45 AM
Post #3 of 21
(1865 views)
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we were told last year that it didn't work so we didn't even try it until yesterday and we just turned it on and it worked. As we sat there, we could feel it going from cold to cool back to cold again
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 14, 2009, 10:03 AM
Post #4 of 21
(1858 views)
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Try pinching off one of the heater hoses going into the firewall and see if that stabilizes anything in the temp.
Also observe to determine if the compressor is actually cutting out when this happens.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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gthomas
User
Jul 14, 2009, 10:08 AM
Post #5 of 21
(1852 views)
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I'll try that tonight, thank you. It is my wides car and work had been done on it be someone last summer so she didn't even try it for a year, until last night and it came on all of the sudden and shocked us actually. That is when we noticed that it worked, then got cool and then cold again....while we sat there we could feel the difference. Driving the car, we noticed it too
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 14, 2009, 10:35 AM
Post #7 of 21
(1841 views)
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LMAO........
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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gthomas
User
Jul 14, 2009, 10:36 AM
Post #8 of 21
(1838 views)
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I'm just tired. What will pinching off the heater hose do?
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 14, 2009, 10:37 AM
Post #9 of 21
(1835 views)
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It will tell me whether it's a problem with the gas side of the system or the temp controls under the dash.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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gthomas
User
Jul 14, 2009, 10:50 AM
Post #10 of 21
(1818 views)
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I popped the hood while the A/C was running and I could see the compressor run for a minute or so and then stop for about 15 seconds. I tried to pinch the heaterhoses but they were too hot and I don't have my tools with me
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Sidom
Veteran
/ Moderator
Jul 14, 2009, 10:55 AM
Post #11 of 21
(1817 views)
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One thing I will add is...If you have access to an A/C gauge set & thermometer it would help alot in pinpointing your problem to be able to give some pressure readings, vent & ambient tempatures. A pair of needle nose vise grips works good for the heater hoses......regular needle nose pliers works as well but you need someone to hold them while you check the vent temps......
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 14, 2009, 10:57 AM
Post #12 of 21
(1814 views)
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If you saw the compressor cycling off frequently, then you need to check the pressures with it running because it sounds like it is either low on refrigerant or has a restriction in the system.
Watch what the pressures do from startup until the changes start.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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gthomas
User
Jul 14, 2009, 11:03 AM
Post #13 of 21
(1808 views)
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Being low on Freon could cause this?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 15, 2009, 1:49 AM
Post #14 of 21
(1790 views)
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OK: If it can coldish to less cool and clutch is cycling AND it's warm out the chances are it's low on refrigerant. Don't add any till you have pressures the other observations at the ready! Please don't use the cans the sell with other than pure refrigerant and a gauge to try to fix this!
Ford relays are a trouble spot but not usually regularly intermittent like this situation sounds like. For other Fords of the era the part is dirt cheap (like under $10 bucks) even from the Ford dealer and is probably clearly marked underhood as to location. If you want to - replace it and if it doesn't change anything save old one as it might also be exact same part # as for fuel pump and as said many (could be chance) have just quit like a blown light bulb to the point I carry the common one in my car for use if I see someone struggling to start this vintage Ford!
For now I think it's low charge issues. If you are not good at this just have the pressures taken and leak checked. Boost or fix leak if thought excessive,
T
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gthomas
User
Jul 15, 2009, 2:09 AM
Post #15 of 21
(1784 views)
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Thanks Tom, it's my wifes car so tomorrow, we'll switch cars and I'll take it to the Shell station down the street and have the freon level checked. Thank you so much for your help.
Thomas Martin
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gthomas
User
Jul 15, 2009, 2:56 AM
Post #16 of 21
(1780 views)
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I'm going to take it in to have the A/C system checked and a tracer added to see where the leak is for $145. (including freon and it will be replaced if it leaks out)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 15, 2009, 3:28 AM
Post #17 of 21
(1774 views)
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Of the checks I suggest that an A/C tech should know....
1. Operating pressures - he or she should be able to temporarily force A/C compressor to stay on and watch.
2. Add if needed (boost system) with the tracer/dye
3. Check clutch air gap - they should know if it's off and some of the Ford compressors are so easy to adjust that taking a shim out it's just a 10 minute job!
4. Check fannage and cleanliness of condenser. I forgot what vehicle this is right now - if it uses a fan clutch inspect that too.
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I just have a gut feeling this may turn out to be a VERY slow leak. Folks can argue the point but a boost if it will last a season vs a possible VERY expensive repair makes sense on an older car. If the problem can't be isolated with electronic detector right away you just need to know how long it works properly so you know the rate of loss. If that car had never been touched since new a decade is a long time and there is a trace amount lost normally - some are so slow they behave over 10 years or more!
OK: Once checked out - get estimates if something is found and hit back. If you are up to doing certain work yourself we are here to help with this. It takes some equipment and bucks even with rented tools to do some things.
Good luck. Let us know how it works out,
T
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gthomas
User
Jul 15, 2009, 3:32 AM
Post #18 of 21
(1769 views)
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Tom, again it's my wifes car and she was livid when I told her that you, and others are saying it is freon. She tells me that the husband of a friend of hers checked all of that out and he says it is a part, on the wheel well that when bypassed, fixes the problem so she has her mind made up that it is this part. I told her to ask her friends husband for the name and location of this part. I can only guess that it is some kind of a relay or electronic part they are talking about
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 15, 2009, 3:58 AM
Post #19 of 21
(1767 views)
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You are probably talking about a LPCO "low pressure cut out" switch (two wire LPCOs can be jumped and compressor will stay on) and if refrigerant is low it will cut out too much and have erratic cooling. BTW it's "refrigerant" - Freon is no longer used since 1993 and was the brand name of refrigerant used then made by Dupont. We know what folks are talking about.
BTW - that switch is there to protect the system!
If it is only that - the switch and these folks know so much about it then why didn't they know you can just screw on a new one. Having the pressures takes will show this! Those switches usually work or not and are not intermittent like how I'm understanding the situation. BUT by all means don't make a fight about it with the wife! - I'm not there making the observations so this is educated guesswork from this end based on the info as we understand it from reading your posts. I could be all wrong or misread something - that happens.
A plain fact is that 2/3rds of poor cooling are caused by low charge of refrigerant which in turn is usually a leak. At some age on it you would expect some loss over time so I was basing suggestions on the odds.
Hey - If you are going to end up on the couch over this for goodness sake do it HER way!
T
(This post was edited by Tom Greenleaf on Jul 15, 2009, 4:00 AM)
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gthomas
User
Jul 15, 2009, 4:05 AM
Post #20 of 21
(1757 views)
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Thank you again. I'm not going to guess and I will take it in to be tested, Friday. The mechanic I was just tlking to said that by bypassing it it would eventually burn out the compressor because it (the relay) is there for a reason
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 15, 2009, 4:18 AM
Post #21 of 21
(1754 views)
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I'll be off line for a while after this post. Know this - bypassing (takes a paperclip) that forces compressor. Even low charge to a point would be cooler if forced. That is also done to charge a system but we don't have the pressure yet and leaving a compressor jumped if in fact the charge is low will eventually ruin the compressor! The refrigerant carries oil with it to lube the compressor and when low it could be inadequate and it would burn it out!
Also - it's there as so when pressures drop even in many normal situation (cold weather being one) such that it won't send liquid refrigerant back to compressor which would cause "hydraulic lock" and also could ruin it.
The car has a high side cut out also to stop compressor from engaging also a protection switch.
All this adds up to you don't know much yet with a system that can work some and cuts out it's compressor without taking pressures - that's the "stethoscope" of the diagnosis for this IMO and is for most issues like it,
T
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