AS-AP temperature control troubleshooting

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Error Code

Temperature difference too large

Coolant temperature sensor malfunction

Carousel temperature sensor malfunction

Cooling system overheated

No error in audit trail, but sampler does not cool at all.

Environment

AS-AP with temperature control

Cause

Failure of one of the temperature sensors

Carousel failure

TEC component failure

Low coolant

Resolution Steps

AS-AP Temperature Unit Troubleshooting Guide_2.pdf

AS-AP Temperature Units Troubleshooting:

I'm in the process of revising the Troubleshooting Guide for temp related issues, but here is the first part of it:

Issue 1:

Unable to turn on the temp control. An error below appears in the Audit trial:

Able to boot and connect to sampler
Sampler can perform startup self-test and regular self-test

Probable cause:

Temp sensor (P/N AAA-069821) on TEC is either defective or the cable connector to the main board is loose

Corrective Action:

Check the cable connector on the main board to see if it’s loose. Correct if loose.
Replace the TEC Assy (P/N 074363) if the cable connector is not loose.

Note: Unfortunately, the sensor is mounted on the heat exchanger body. It’s very difficult to get to.

Displayed Error in Audit Trail:

Error] {Sampler} Coolant temperature sensor malfunction.

Turn the autosampler off and on again or perform a self test.

Troubleshooting steps:

The Error message Coolant temperature sensor malfunction indicates a failure on the temperature sensor in the TE Peltier Cooling unit.

To verify this failure put CM into Service Mode. Then with the unit powered up and cooling maximum commanded open a command window by pressing the F8 key on the keyboard. Now right click on the open white space of the window and select service in the list. Expand the sampler commands by clicking on the + next to Sampler. Type p over and over on keyboard till you get to the prop_TempCoolant property and click on it. If the unit has not been cooling very long it should be a few degrees C below ambient only or if on for a while close to set point. If it is too high or low then this sensor is failed. Note the prop_TempSink sensor is not used in the AS-AP so it will read zero. There are only two temperature sensors in an AS-AP.

If the prop_TempCoolant sensor has failed you would need to replace the complete TE Peltier cooling unit.

Troubleshooting Note 1: If you have an AS-AP spare part temperature sensor P# 069821 you can use it to troubleshoot this failure by disconnecting the TE Peltier sensor from the Main CPU on J13 and then install your known good sensor on J13 of the Main CPU board. Then check the F8 property prop_TempCoolant temperature value. If working correctly you should see a temperature value near ambient in degrees C.

Troubleshooting Note 2: In some rare failures the main CPU which the temperature sensors connect to VIA a serial bus has failed. This can be caused by Main CPU failure or a sensor failure pulling down the bus. Check the carousel sensor prop_TempCarousel also to see if the CPU serial bus is functioning to verify CPU is OK. If you can see a valid temperature on this sensor then the bus is working and not pulled down so you can trust the prop_TempCoolant is correct. If both sensor readings are very low or very high (Out of set point range) then unplug each sensor one at a time from Main CPU (J2 = TempCarousel / J13 = TempCoolant) and then check for which one is causing a failure. If both still do not have a valid reading replace Main CPU board.

Displayed Error in Audit Trail:

Error] {Sampler} Carousel temperature sensor malfunction.

Turn the autosampler off and on again or perform a self test.

Troubleshooting steps:

The Error message Carousel temperature sensor malfunction indicates a failure on the temperature sensor in the Bulkhead were the coolant flows in/out of the carousel.

First verify the cooling system pump and TE Peltier Fan is running at the back of the unit. You may need to remove the rear cover to see the pump motor turning. The pump has black rounded cover at bottom of pump that spins at high speed so be careful.

Then with the unit powered up and cooling maximum commanded on open a command window by pressing the F8 key on the keyboard. Now right click on the open white space of the window and select service in the list. Expand the sampler commands by clicking on the + next to Sampler. Type p over and over on keyboard till you get to the prop_TempCarousel property and click on it. If the unit has not been cooling very long it should be a few degrees C below ambient only or if on for a while close to set point. If it is too high or low then this sensor is failed. Now check the prop_TempCoolant and you should see a temperature below or close to the set point. Note the prop_TempSink sensor is not used in the AS-AP so it will read zero. There are only two temperature sensors in an AS-AP.

If the prop_TempCarousel sensor has failed you would need to replace the carousel bulkhead with temperature sensor (carousel assembly).

Troubleshooting Note 1: In some rare failures the main CPU which the temperature sensors connect to VIA a serial bus has failed. This can be caused by Main CPU failure or a sensor failure pulled down the bus. Check the TE Peltier sensor prop_TempCoolant also to see if the CPU serial bus is functioning to verify CPU is OK. If you can see a valid temperature on this sensor then the bus is working and not pulled down so you can trust the prop_TempCarousel is correct. If both sensor readings are very low or very high (Out of set point range) then unplug each sensor one at a time from Main CPU (J2 = TempCarousel / J13 = TempCoolant) and then check for which one is causing a failure. If both still do not have a valid reading replace Main CPU board.

Displayed Error in Audit Trail:

There is no error in Audit trail but unit does not cool the samples at all.

Troubleshooting steps:

To troubleshoot this failure put CM into Service Mode. Then with the unit powered up and cooling commanded to maximum on (4 or 5 degrees C set point).

Verify the cooling system pump and Peltier Fan is running at the back of the unit. You may need to remove the rear cover to see the pump motor turning. The pump has black rounded cover at bottom of pump that spins at high speed so be careful. If not then the Main CPU is not turning it on. Replace main board. If pump is on continue troubleshooting below.

Wait several minutes and place your hand on the inside carousel surface and feel if it is getting cold. If it is not then open a command window by pressing the F8 key on the keyboard. Now right click on the open white space of the window and select service in the list. Expand the sampler commands by clicking on the + next to Sampler. Type p over and over on keyboard till you get to the prop_TempCoolant property and click on it. If the unit has been at maximum cooling for 10 to 15 minutes and the prop_TempCoolant temperature is very low at – 5 or lower then you most likely have a carousel that has leaked all of the coolant out of the cooling system.

Check for Leaks on carousel or tip unit on side and see if coolant comes out of chassis.

You can check the prop_TempCarousel sensor by clicking on it just below prop_TempCoolant and if it reads close to ambient temperature this verifies a leak has occurred in the cooling system.

Displayed Error in Audit Trail:

Troubleshooting steps:

Verify that the Fan that is in the back of the peltier unit is running if Cooling is commanded on. If the fan does not run the peltier unit on the back will overheat. Note: When the unit is set to cooling the peltier back fins get hot and when the unit is set to heating above ambient the peltier back fins get cool. The peltier fan is driven by a control circuit on the main CPU board. If the unit will not let cooling to start at all after it has set for 60 minutes or more in off condition then a temperature sensor may have failed in the unit indicating a overheat condition when one does not exist.

Checking the Temperature Sensors: To verify this failure put CM into Service Mode. Then with the unit powered up and cooling commanded on open a command window by pressing the F8 key on the keyboard. Now right click on the open white space of the window and select service in the list. Expand the sampler commands by clicking on the + next to Sampler. Type p over and over on keyboard till you get to the prop_TempCoolant property and click on it. If the unit has not been cooling very long it should be a few degrees C below ambient only. If it is too high (Out of normal Range of AS-AP) or low (ZERO) then this sensor is failed. In the case of the message above the reading would be very high.

If the prop_TempCoolant sensor has failed you would need to replace the complete peltier cooling unit.