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A/c Cutting Off During Trips


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Hello! I have a '97 LX450 and I'm having a strange issue with my AC. Here is what's going on.

1) It seems to cut off during trips.

2) When I drive around town, it's fine.

3) When I drive at interstate speed for longer than an hour or so, the AC cuts off (60 mph or faster).

3a) When not interstate speed, still cuts off, but normally cuts off after a 1hr & half to 2 hrs.

4) Sometimes the AC comes back on and sometimes it doesn't. I think it's an electrical issue, b/c the AC comes back when I hit a bump in the road (but only sometimes)

5) When I stop for gas, then continue my trip, the AC works fine, but for only 5 minutes of so and then it cuts off again.

I took my car into a reputable A/C mechanic earlier this summer, but they couldn't duplicate the issue, so they couldn't correct it - again, only happens during trips longer than a hour.

Anybody have a similar experience? Any advice and/or troubleshooting tips would be greatly appreciated.

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Most likely you're engine is getting too hot. In order to reduce the load on the motor, the AC system has an automatic shutoff if the coolant temperature reaches 226 Degrees F. So this is not good. It's an indication that your coolant system is not running up to par. It's particularly important on these vehicles that you keep your coolant system in as prestine operating condition as possible, because this engine is prone to blowing headgaskets. And the best way to help prevent that is to keep the coolant system in good shape.

Things to do to keep the system in top shape:

-New t-stat

-New Fan clutch (if it's original, it's about a certainty it is not working correctly anymore)

-Do a coolant flush about every 18 to 24 months

-Make sure you're not leaking any coolant, there is one hose in particular that's hard to see and hard to get to that will bulge - and leak after time.

-Take the cap off the radiator and check for sludge along the top of the radiator cores. If you've got this report back.

Keep in mind that your factory temp guage has a built-in dead spot in the middle, so as the motor warms up, it will rise to the center and stop until the temperatures get really hot (around 230 degree f) and then it starts moving again. So your motor could be getting hot enough for the AC to cut off and your temp gauge not even move. The problem is the added heat puts added strain on what is considered by many owners to be an inadequate headgasket design.

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  • 2 weeks later...

If all else fails you may consider that the A/C needs to be serviced. Although you stated that it could not be duplicated at an A/C shop, take it to another shop and have a complete inspection and diagnosis.

I have had the symptoms you describe in other cars (Ford and Porsche) when the A/C needed a recharge.

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  • 3 weeks later...

It's possible you got low on freon and sucked some air and moisture into the system. Any moisture can freeze in the expansion valve and cause this symptom. If you can turn the heater on for a while and then have the AC come back, it is a good indicator of this situation. (Iknow this is a tough thing to do on a hot trip) If you are low on freon you might consider replacing your dryer/receiver, having the moisture pumped out with a long vacuum and then recharged with freon.

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