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Old 30 Apr 2011, 04:27 pm
AlphaBob AlphaBob is offline
Fresh Cruiser
Join Date: Apr 2011
Posts: 6
Default A/C issue - Couple Thoughts & Fan Relay Questions

Just joined this morning, my first post ...

2007 PT Cruiser
46,000 miles
Fairly Basic Model
Wife is Primary Driver (until something breaks)

Having problems with my AC also. Trying to diagnose. My air actually blows cold for long periods of time and then will blow warm.

First place I wanted to check is the fan. I've read:

(i) That the fan should always turn on when the AC button is pushed. I push the button, hear the AC Clutch Engage (it puts a load on the engine and you can hear it sort of pulse as the engine adjusts to the higher working load). BUT - no fan. I had the hood open in the driveway, got out and look carefully and the fan definitely does not run. (I'm in Florida and its 81 F today).

(ii) Possibly related, my wife reports that the car has had issues of really idling rough at stop lights when the AC is on. If I understand other posts correctly, the radiator fan should run constantly when the AC is turned on and if it isn't working, the extra work load from the AC will really make it idle roughly until the high pressure switch trips off the compressor. All of this information reasonably describes my situation.

So here's my unique problem:

I've located the fan relays - they are located on the passenger side of the fan shroud. I understand how to test the relays and how to jumper out the relays to test the fan motor. HOWEVER (!) I cannot get the darn things out! They are marked "Tyco" on the top so I think that I'm looking at the right component. There is a plastic clip on the shroud side and when I release the clip the relay will lift straight up and off its mount. The problem is I cannot release the relay from the wiring bundle that comes up from underneath.

There is a second plastic clip located on the firewall side of the relay. Remember the clip to release the whole unit (wires still attached) is on the shroud side. The clip on the opposite side of the relay (fire wall side) looks like it should pop open and the wiring harness should pull out of the bottom of the relay. If I could do this the rely would come out and the wire (and presumably male plug) would stay in the vehicle.

Everything is very tight - but I've been able to open the second clip (again the one that connects the relay to the wiring harness that comes up from the bottom. However, it doesn't want to pull apart.

Has anyone ever had this experience and am I missing something?

Finally, back on the pressure questions related to this post:

My Xterra AC requires 35-50 PSI on the low side and 225-275 on the high side. If you're reading your pressures on the low side, you're high. 60 - 70 won't kill it, but it is hard on the compressor. My Xterra is "high on the low side" because that's what it takes to get the high side up to the minimum of 225 PSI. However, my compressor (or the electric clutch) is dying on that vehicle so an overcharge is sort of palliative care.

The Harbor Freight HVAC Gauges are a pretty good investment if you're going to be "messing about with cars". They are typically on sale for $44 and you should be able to scare up a 20% off coupon. The pressures for my Xterra are fairly common for auto AC so you wouldn't be too far off if you used them.

That's all I've got on the pressures, but think that you might have similar problems on the fan side.

Finally, do we know for sure sure sure that the fan should come on when the AC is switch on? My guess if that is true is that my slow fan relay is shot and that my vehicle doesn't overheat because the high speed relay kicks on the fan when it gets hot. (Just a guess).
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