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A/c Problems


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I'm fairly new to this site and so forgive me if there is already a topic on this.

I bought a silver '91 LS400 in March. It has 204,000 miles on it currently. I bought it with 198,000.

Since it was cold here in March, I didn't use the A/C when I was test driving it. Now it's June and 90+ out and I definately need it. Only problem is when I turned it on all it did was blow hot air from outside. I brought it to a shop and had them convert the system to 134 and recharge it. All that did was make it so when I turned on the A/C the light above it would blink. I then read about the RPM sensor for the A/C sometimes got dirty, so we took 2 cans of engine cleaner and soaked the whole area where the pump is. That didn't work.

My option now is to have the A/C pump replaced. I don't know for sure if that will fix my problem though, so I'm wondering if anyone could give me some insight on what the problem is I'm having.

All of your help is greatly appreciated.


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3 questions come to mind..1. what was replaced on the conversion? 2. Do you still have a charge? 3. Doe the compressor kick in? Lets start there. Remember the sensor contacts are underneath the compressor and must be removed in order to clean them.

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I did not know that about the sensor contacts.

When the guys converted the system, i think all they did was evacuate the freon out of the pipes, put new fittings on the ports, and then fill it with the 134 freon. The pump does not turn on at all, and I haven't checked to see if it has a charge. It has been doing the same thing since the moment it came out of the shop for re-charging though so I don't think it's a leak.

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Since you paid them $200, i would take it back to them and have them check the pressure. That will tell you if there's a leak. If the pressure is low, get some R134 leak detector (has dye in it) and recharge system. Then check all AC hoses and connections for presence of dye. Check at compressor, air dryer, firewall, and along all hoses. AC compressor will not start up if pressure is low.

If pressure is good, may have a bad compressor. AC light on dash should be flashing if compressor is locked up. Could also be AC clutch. There's a way to test the clutch for engaging - maybe others can provide details.

Let us know what you find.

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Alright, well thanks for your info on the dye, but since you said that if the light is blinking then it's a problem with the compressor I will go with that approach.

If the way you check the clutch is to mess with the fuses and check for charge in the A/C fuse box then that is what I've already done. Everything looked fine as far as that went, so I'm gonna go ahead and have the compressor replaced.

Wish me luck.

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