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Hi, I have one of the two Reattas over here in England and my aircon has stopped working and I'm hoping that you can help me.

When I press the "auto" button it immediately reverts to "econ" and won't blow cold, only ambient temperature.

I've had the gas checked and it's OK.

The fuses are OK.

I've checked the A/C relay in the underhood relay centre and it works.

I've jumped terminals 1 and 4 on the relay cavity and the compressor clutch cuts in.

I've jumped terminals 1 and 2 on the relay cavity and the compressor clutch cuts in.

Terminal 5 gives around 12.5V.

At the ECM the DK GRN/Yellow cable at Cavity 15 gives 12.5Vish.

Everything else appears to be working, car runs well etc.

I thought that I might have inadvertently switched off the compressor in diagnostics and therefore re-entered diagnostics and set ES06 to "99" but it didn't help.

Is it the ECM and if so, can I fix it myself?

The car is a 1990 model built in November 1989 and has done only 132000 miles.

Any help will be much appreciated.

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Welcome to the forum!

 

The AC switching to ECON is happening because the BCM senses there is a problem. Usually the problem is low Freon  You say that you had the gas checked and it's OK but you can't check it properly without the compressor running.

 

Here are some things you should try first.  Disconnect a battery cable and leave it off for a few minutes then reconnect it. That will reset the compressor and clear any codes.  Try the AC and see if the compressor will engage and keep running when you press AUTO.

 

If it still goes to ECON when you press AUTO   go into diagnostics and check to see if any codes are present.  Write down any codes and report back here with the codes you have.

 

Next: If the AC still goes to ECON disconnect the battery as you did before to reset the compressor and clear the codes.  Then disconnect the Low Pressure Switch, shown in the photo below, and put a jumper across the pins in the electrical connector (not the switch). You can use a paperclip but be careful and don't use one large enough that you have to force it in. It's easy to damage the connector.  Doing this should trick the BCM into thinking the system has enough Freon and the compressor should come on.  If it does that proves you are low on Freon or have a bad Low Pressure Switch.  Don't let the compressor run long with the jumper in place. It could damage it if you are low on Freon.

 

Let us know what you find.

ac_sensors.jpg

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Many Thanks for the Speedy Reply!

At present it's pouring with rain over here ( stereotypical weather for England) and the car is under a cover and I won't be able to get at it until tomorrow.

However, I can tell you that I had code b447C come up.

I'll get back to you tomorrow.

Regards, Paul.

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Code B447 is telling you that you are very low on Freon.   When that code is set the compressor is locked out to prevent damage until it is reset.  There is a small chance that the Low Pressure Switch is bad but I'll bet you don't have enough Freon in the system.  My previous instructions will be helpful.

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I don't think this is it as Ronnie has a good handle on this, but you might want to jumper the switch in the rack and pinion that kicks the A/C out when making a turn. Long shot but something to be aware of.

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I would replace the low pressure switch first, as it is cheaper and easier to do.

I think Ronnie is on the right track. If you are low on freon, you will at least have new low pressure switch.

When this happened to me the switch was bad.

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Hi All, Many Thanks for your recommendations.

This morning I cleared the codes b552H and b447C, disconnected battery for 5 minutes and started the car.

Pressed "auto" on AC panel, set temp to 60 and AC started to work......

A very few moments later it changed itself to "econ".

Checked codes and found  b446C and b447C.

Cleared codes, disconnected battery, jumped terminals on low pressure switch, restarted car and pressed "auto" and again, it ran for a short while then changed itself to "econ".

I think that the aircon "tech" didn't realise that the compressor must run in order to tell whether there is enough gas in the system.

The man that I usually have is on holiday for the next two weeks and so I saw his stand in.

Is it worth getting a new low pressure switch for when he gets back, just in case? I expect that you have to evacuate the system to fit a new switch.

If so, do you know the part number? Is it ACDelco 15-5643?

Any more assistance will be much appreciated!

Best Regards, Paul.

 

 

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3 hours ago, libstainedglass said:

Checked codes and found  b446C and b447C.

Cleared codes, disconnected battery, jumped terminals on low pressure switch, restarted car and pressed "auto" and again, it ran for a short while then changed itself to "econ".

I think that the aircon "tech" didn't realise that the compressor must run in order to tell whether there is enough gas in the system.

The man that I usually have is on holiday for the next two weeks and so I saw his stand in.

Is it worth getting a new low pressure switch for when he gets back, just in case? I expect that you have to evacuate the system to fit a new switch.

The BCM is definitely detecting a low Freon condition.  Usually jumping the low pressure switch will allow the compressor to keep running long enough to add Freon without changing to ECON. Are you sure you jumped the low pressure switch and not the low temp sensor? 

 

If you are certain you had the Low Pressure Switch jumped you might want to try Dave's suggestion of putting a jumper on the power steering pressure switch.  That switch being bad can keep the BCM from engaging the compressor.  However, on my '88 that switch will not cause the AC to go into ECON when it disengages the compressor. Your '90 could be different.

 

A lot of AC techs don't know how to get the compress to engage again after the BCM has locked it out. That might be the case with the guy who told you the Freon was OK. He might have just assumed the compressor was running.  When you get him to check it the next time print off this page and show it to him so he will have a better understanding of the AC system on the Reatta.  Compressor Kicks Out When Adding Freon - Solution

 

I would go ahead and change the Low Pressure Switch just to be on the safe side.  As Jon said, it is a relatively cheap part and you can do it yourself without losing hardly any Freon. No need to evacuate the system.  The fitting the switch screws onto has a schrader valve that will prevent much Freon from escaping.  If it's legal in  your country you  might want to get a Freon refill kit at the auto parts store and add some Freon yourself.  That's what I do.

 

Most any auto parts store will have it in stock (in the USA. don't know about England).  If you have any doubts about getting the correct part take you old one off and take it with you to the parts store.  This is what the switch looks like.  Some brands are black in color instead of silver. Sorry I don't know the part number but the parts store should find easily. 

ac low pressure switch.jpg

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I remember my experience with the pressure and temperature switches on my '90 and they are not only a different style, they are also located differently than the posted diagram. The low Freon pressure switch is located approximately where the high side temperature switch is indicated in the diagram, and the high side temperature sensor is way over towards the drivers side. You may have the wrong sensor.

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Hi, Yes I eventually found out that the low pressure switch on my car is further over to the driver's side.

Does anyone know the ACDelco part number? I've found out that the 15-5643 is incompatible with my car but the 15-2490 is compatible except for the fact that it is listed as the high side pressure cut out and not the low side. Very, very few switches listed as "low side".

No-one in England is listing anything like this so the option of taking it to a parts store isn't available to me.

It's ebay.com or Rock Auto who list 15-5643 but not as suitable for a Reatta.

I'll keep searching the internet tomorrow.

Thank you to everyone helping me here.

Regards, Paul.

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Sorry that I mislead you on the location of the low pressure switch.  I didn't realize they had moved switches and sensors around on the '90 models. Thanks to 2seater for catching my mistake.  Did the compressor stay engaged when you jumped the correct switch?

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Ronnie, I don't think you misled, locations don't match my FSM either. Just to be clear: the two temperature sensors are both located in the smaller diameter high pressure line, one near the turn into the evaporator immediately downstream of the orifice tube and the other, the high side temperature, is almost directly to the rear of the EGR valve. The single pressure switch is almost exactly centered between the two temp. switches and is located on the larger return or low pressure line.

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I tried a Rock Auto search too and it is rather confusing, if not downright misleading. Nothing shows up searching under the car model itself but searching on 15-2490 brings up what appears to be correct for both the Reatta and Riviera in the correct years. Clicking on the part catalog seems to come up under Riviera but in any case, you need to go to a sub-menu either within the "a/c compressor and component kit". At the top left of the heading is "related parts" and a bunch of pressure switches show up but it must be sorted through.

 

In other words, the 152490 part number looks correct but I have no direct way to verify.

Edited by 2seater

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I often catch myself making the mistake of assuming all Reattas are like my '88. But as Dave points out a lot, not all Reattas were created equally. 

 

31 minutes ago, 2seater said:

In other words, the 152490 part number looks correct but I have no direct way to verify.

I had looked earlier on RockAuto to find the part number for the low pressure switch and didn't have much luck. I thought the reason I couldn't find it was because I was having a senior moment. 🙂

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3 hours ago, libstainedglass said:

No it didn't. It engaged for a few seconds and then reverted to "econ".

That's really odd.  You should jumper the low pressure switch, go into diagnostics and look at BCM input BI08 to see if it reads HI. If it does that will verify that the BCM knows the jumper is connected. If BI08 isn't reading HI you will need to determine why it's not.

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3 hours ago, Ronnie said:

I often catch myself making the mistake of assuming all Reattas are like my '88. But as Dave points out a lot, not all Reattas were created equally. 

 

I had looked earlier on RockAuto to find the part number for the low pressure switch and didn't have much luck. I thought the reason I couldn't find it was because I was having a senior moment. 🙂

No senior moments, it really is sometimes obscure. After I used the part number from our British friend, it helped narrow the search area and then I found they have stuff in a sub-menu that I had not encountered before. If you click on the heat and a/c, you must look under a/c compressor and components, which is just a bunch of compressors and then on the "related parts" menu to find the switches. There are several pressure switches listed, including the Delco one, but I never would have found that without the suggested part number.

Not only are some of the locations different, the temperature sensors are not interchangeable between some years either. Thread size and electrical connections are completely different, but it appears the pressure switch is the same for all years. 

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HI, I've done some more research and it appears that ACDelco 15-2490 is the correct part.

At the very bottom of one listing on ebay for "High side pressure switch" it states that it is, in fact, the low side switch.

Raining again here in England so no practical work today.

Thank you all again for your input.

Regards, Paul.

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Hello Again,

I have a new low side switch 15-2490 arriving later this week and currently have B108 reading "Hi".

Current codes are B446H and B447C with low pressure switch terminals shorted.

Pressing "auto" makes it jump back to "econ" immediately.

What I can't do is locate the power steering pressure switch but I've only tried to see it from the top.

Do I need to get underneath to find it?

Air con man should soon be back from his holiday.

Any help will be gratefully received.

Regards, Paul.

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Back Again,

I've just been reading the stuff about ECMs/BCMs from epssax and Ronnie posted some charts titled "ECM Diagnostic Codes" and underneath  one called "Diagnostic Code Comments".

In this chart it has "E  Switches climate control mode to Econ if in Auto" which is exactly the problem that I am having with mine.

Only difficulty for me is that I don't understand what  "comments" means exactly.

Regards, Paul.

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