QuestionQUESTION: Hi. I just bought a 1997 Suzuki sidekick sport for my son. A mechanic checked the A/C system because the compressor would not kick on. He bypassed the relays and it worked. I bought new relays and tried it. It did not kick on. Is this because of ambient temperature? I was doing this on a 25* morning......
ANSWER: In most circuits involving relays, there are two parts: the controlled and the controlling. Unfortunately, when you bypass relays, you actually take the 'controlling' portion of the circuit out of the equation. Jumpering the 'controlled' portion really bypasses the circuit logic. For example, the controlling aspect lies in the various feedback sensors and switches (pressure cycling, high pressure cutout, low pressure cutout, etc.) that determine when to trigger the controlled -- in this example, the compressor clutch apply.
You really need to determine the reason the controlling circuit is not complete -- whether it be a pressure switch malfunction, an open circuit, or a low refrigerant condition. There are other reasons the compressor will not engage, but those are most common. As of now, you do know the controlled portion is working, so half of the circuit is checked out. Now, just find out what's wrong in the first half, and you're all set! Good luck!
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QUESTION: WOW. Thats alot of good info, thanks. i have checked the refrigerant, and it is within pressure range. Is there an easy way to check the pressure switch? I was really hoping it was due to not asking for cold air due to temp. I was working in...wishful thinking.
AnswerIf you're a DIY guy, I'd suggest subscribing to something like www.alldatadiy.com -- for $25, you get a 1 year subscription to some pretty darn accurate service info. At Suzuki, you can also get service manuals and stuff at
http://www.suzukipitstop.com/home/vehicleInfo.asp
That said, this problem can be really easily, but most times access to wiring diagrams and factory troubleshooters is very beneficial. Are you sure about the pressures? It can only be checked accurately while the compressor is engaged and running, and the low side should typically read around 28-35psi. The low pressure cutoff switch (or whatever Suzuki calls it) will open at around 21-25psi, probably, so be careful. Depending on the type of A/C system, this switch is usually found on the low side (obviously), near the accumulator.
Likewise, the system will shut off above a certain pressure as well, so the high pressure cutoff switch (on the high side, probably very close to the compressor output -- on the condenser line) could be the cause as well. Normally, though, unless the A/C system has some sort of logic, the compressor will engage initially, and either short-cycle, or not engage once it's tripped. If the system is never engaging, I might look at an open on the controlling portion of the circuit. Since it's a Suzuki, I wouldn't expect an advanced system, so tracking this down without service info is possible. Any switch on a completely manual 'controlling' system can normally be jumpered for testing -- they are either ON or OFF. However, jumpering anything without the service info in front of you is a risky bet. Good luck!
