Troubleshooting the E-4B Heat Sink Probe Overheated

Overview

This error occurs when the temperature of the heat sink probe is greater than 176°F (80°C).The heat sink probe measures the temperature of the I/O board triac heat sink. The heat sink probe is mounted to the I/O near the front of the unit.

Note: Image is a bird's eye view from the top, with the cover removed.

Field Troubleshooting

To avoid electrical shock or property damage, disconnect power before installing or servicing equipment. A qualified technician must perform the service procedures.

Note: you can view the heat sink probe temperature by navigating to Home/Settings/Temperature Display (swipe left 10 times). The Heat Sink Temperature is located in the upper left corner of the Temperature Display.

1. Unplug main power to unit and turn main power switch to off position.

2. Remove the top cover of the unit to gain access to the electrical components.

3. Visually inspect that both cooling fans are clean from dust and debris.

4. Turn on the unit (fans run after the unit is powered on for 30 seconds).

5. Verify both fans are running.

   • If fans are clean and running, skip to step 6.

   • If the fan(s) are NOT running, ensure 12VDC is supplied to the fan. If voltage is present, replace fan.

6. Allow unit to run until the E-4B error occurs, and then disconnect UHC from power supply.

7. Take a surface temperature reading on the heat sink, where the probe mounts, to see if the heat sink is truly overheating (reaching temperatures greater than 176F (80C)). If it is, replace the I/O board; otherwise, continue at step 8.



8. Unplug the Heat Sink Probe connector from J9 at I/O board.

9. Ohm out the probe using the RTD Chart below.

   • If the reading of the probe is within +/-5F of the heat sink probe surface temp reading, check for loose or faulty connection to I/O.

   • If connection is tight and a new probe produces same result, then replace I/O board.

   • If the ohm reading from the probe is +/- 5F from the surface temperature reading, replace probe.

RTD Chart

Temperature (Fahrenheit)	Temperature (Celsius)	Resistance Ohms
50	10,00	1 039,02
60	15,56	1 060,65
70	21,11	1 082,24
80	26,67	1 103,80
90	32,22	1 125,32
100	37,78	1 146,81
110	43,33	1 168,26
120	48,89	1 189,67
130	54,44	1 211,05
140	60,00	1 232,39
150	65,56	1 253,70
160	71,11	1 274,97
170	76,67	1 296,20
180	82,22	1 317,40
185	85,00	1 327,99
190	87,78	1 338,57
200	93,33	1 359,69
210	98,89	1 380,79
212	100,00	1 385,00
220	104,44	1 401,84
230	110,00	1 422,86
240	115,56	1 443,85
250	121,11	1 464,79
260	126,67	1 485,71
270	132,22	1 506,58
280	137,78	1 527,43
290	143,33	1 548,23
300	148,89	1 569,00
310	154,44	1 589,73
320	160,00	1 610,43
325	162,78	1 620,77
330	165,56	1 631,09
340	171,11	1 651,72
350	176,67	1 672,31
360	182,22	1 692,86
365	185,00	1 703,13
370	187,78	1 713,38
380	193,33	1 733,87
390	198,89	1 754,31
400	204,44	1 774,72
410	210,00	1 795,10
420	215,56	1 815,44
430	211,11	1 835,74
440	226,67	1 856,01