Coolant temp sensor - blue or green?

[buster]

Why is it always me?

I feel like banging my head against a wall sometimes.

My car would not start and I was told by one of these roadside diagnostic peeps that the temperature sender unit was telling the CPU that the engine was warm when it wasn't. Hence, no fuel enrichment for a cold start.

The garage I took it to changed the 4 pin temperature sender in the bottom hose and hey presto, it started fine in the morning, but the temperature gauge didn't work on my trip to work (about 5 miles) yet it used to be at 90 in about 2 miles.

Also, when hot the car would judder when it changed up a gear (Auto) or when I let my foot off the throttle. It also stalled once.

I took it back and they cheerfully charged me £70.00 to diagnose it. They told me that the secondary air pump was tired and the water pump was not working?

Nothing about the coolant temperature sensor.

As this was around £1,000 to fix I took it away and refused to have it done as I really thought there was something amiss here (The water pump had been replaced 8 months beforehand)

After a lot of digging I have found that Audi had changed the 4 pin switch in the bottom hose back in late 1998. Because of the change, a new colour was used to stop people fitting the wrong type. Old ones (fitted to Pre 1998 cars) are blue, new ones (fitted from beginning of 1999) are green.

My car, a late 2001 model should have been fitted with the green one; it was fitted with the blue instead.

Anyone know what the difference between these switches are, and if the wrong switch could cause the problems I have?

Please someone help as I am faced with yet another £160.00 bill to fix this bit now.

[buster]

Update

Took the car back to the garage who fixed it

I said the sender should be green, the one they removed and showed me was green and it is now blue! I didn't actually accuse them of fitting the wrong one, but they did take it rather personally.

They told me that they did NOT change that sender (In the bottom hose), they changed the one at the back of the engine on the offside, then showed me where it was, and sure enough it was green. Did I look silly? I was then told that the one in the front hose was a switch to turn the fan on, and the green one at the back was the coolant temperature sender.

I asked why the one in the bottom hose looked new and they told me that they had taken it out to check it. It looked new because they had cleaned it. Looked even sillier now; apologised and left.

Took it to another garage this morning and they took the green sender out (the one at the back of the engine) This was supposed to be the new one as fitted a week or so ago.

I have a picture of it and will upload it later. It is as old as the car, and one of the pins was almost corroded away. I am now not a happy chappy.

I was lied to and made to look stupid.

When there I mentioned that the water pump was reported to be suspect and the secondary air pump was tired. They tested the secondary air pump whilst I was there and it went off like a brand new vacuum cleaner. Didn't sound even slightly tired and the opinion of the Audi expert I had taken it to, was that it was in perfect condition, but a pipe underneath it had broken, causing the errors to be logged.

The water pump failing would NOT cause the engine to run cold, which is exactly what I thought. The garage who told me that it had failed, even tried to explain to me why it would make the engine run cold.

Moral?

Don't trust everything you are told by garages, and just because they look like they know what they are doing, doesn't mean they don't use the, "let's put a new one of these on and see if that works," system!

I am not going to name the garages, just in case I am wrong

I will dig a huge hole and hide in it if I am LOL