Blinking A/C light on my 2003 Toyota 4Runner. Must have a slight leak, I would add refrigerant from a can and be good all summer. This year although I replaced the A/C relay the a/c light on the dial flashes and I get hot air. My compressor starts to engage and instantly cuts off. While engaged for that second or two a tin can rattle type sound occurs and the pressure drops to zero. With the engine off the low side pressure reads high and is slightly beyond the beginning of red zone (alert). Any general experiences or possibly with those V6 4Runners would be much appreciated.

  • Welcome to Motor Vehicle Maintenance & Repair! May 30, 2018 at 0:54
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    Sounds like it's time to have your a/c looked at. Your compressor cycles because of changes to pressure in the ac system. The tinny sound is the compressor kicking off/on and is a normal sound, though when it happens at increments you're talking about it tends to seem like a problem. I'd get a UV light and trace your leak. If you don't fix it, you'll eventually burn out your compressor. May 30, 2018 at 4:26
  • These Denso compressors usually feature a shaft speed sensor mounted on its body (usually the belly). This sensor monitors if the shaft is experiencing any binding and feeds the speed to the a/c amplifier. If any excessive differential between the engine speed and the compressor shaft speed is detected the compressor is immediately shut off to avoid the consequences of a compressor seizure. If the compressor is cycling due to internal binding, the compressor may have already been damaged. Possibly due to lack of refrigerant oil (when you have a leak, oil leaks with the refrigerant).
    – Al_
    May 31, 2018 at 23:10

1 Answer 1


Thanks to all for the help, much appreciated. A garage emptied/vacuumed and then system took the refill. When I tried refilling without vacuuming my refill wouldn't get sucked in. I'm thinking that this year I waited too long to refill. In previous years I refilled in early spring.

  • If in the past you've regularly refilled or topped up the refrigerant in the A/C system, then the system has a leak. A sealed system, run occasionally to keep its seals healthy (they're lubricated by oils ini the compressor) should run for years without topping up. I just sold a 2001 VW Passat; the A/C worked very well and the system had been recharged/topped off only once during the eighteen years I owned the car. Jul 3, 2018 at 15:51

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