AC and oil light on 98 2.8, Quattro shuts off

When the outside temp is high at 90+, the oil light keeps coming on although all fluids check OK. As the temp guage rises, often the AC shuts downand and hot air
blows. I have then set the Temp to 80+, then reduce it to 68 or so and the AC goes back on most of the time. If I put in manual for a while it will also kick in when i set itt to Auto. Bad thermostat????
thanks for your help. Bob
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Bob Libutti wrote:

all fluids check OK. As the temp guage rises, often the AC shuts downand and hot air blows. I have then set the Temp to 80+, then reduce it to 68 or so and the AC goes back on most of the time. If I put in manual for a while it will also kick in when i set itt to Auto. Bad thermostat????
You need to pull the codes and not just replace parts.....
Dan D '04 A4 1.8Tq MT-6 Central NJ USA
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all fluids check OK. As the temp guage rises, often the AC shuts downand and hot air blows. I have then set the Temp to 80+, then reduce it to 68 or so and the AC goes back on most of the time. If I put in manual for a while it will also kick in when i set itt to Auto. Bad thermostat????
My son has the same car. He's had it for nearly a year. On hot days the oil light comes on at random intervals. We haven't been able to pin down anything other than heat that is a common denominator. [Oil temp gets to 185 or so and it is liable to light up any time] Can you get the light to go off when you lower the AC temp?
Sometimes it comes on at idle, sometimes at 40, sometimes at highway speeds. It goes off just as randomly.
Replaced sending unit last year- but that didn't change anything. Put a pressure gauge on it and though the pressure is slightly less than specs, it isn't alarmingly low. [I posted the specifics last year]
Tried a heavier weight oil. No change. We'll by putting a 10-40 synthetic in it next week.
The dealer found no codes stored & said they could diagnose it in 2-3 hours. [but wouldn't speculate further]
Your lack of AC isn't something we noticed-- though I *think* after changing the auxiliary fan [the electric fan that cools the radiator] the light didn't come on for a long time. When that fan isn't working, the AC won't work.
My gut says that it is an electrical problem-- a poor ground, or intermittent open. One of these days I'll go through the Bentley wiring diagrams to see what grounds or circuits that fan or the AC shares with the oil pressure gauge.
[Lately it seems like if the wipers are on it is more likely to trigger the oil light. . . imagination?]
Jim
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