Danfoss Turbocor TT Series, Service Manual, Page: 117 / 294

1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Remove the Soft Start. Refer to Section 4.14.4 Soft Start Removal (Closed-Top).
3. Flip the Soft Start to access the fuses. Refer to Figure 4-98 Soft Start Fuse Locations on page 116 for
detail on the fuse locations. Refer to Table 4-24 Soft Start Fuse Details for fuse detail.
4. Using a multimeter set for resistance measurements, place the leads on the ends of the F1 fuse. The
reading should be less than 1Ω.
l
An open F1 fuse may indicate a problem with the Potted DC-DC
5. Using a multimeter set for resistance measurements, place the leads on the ends of the F2 Nano fuse.
The reading should be less than 1Ω.
l
An open F2 fuse may indicate a problem with the Potted DC-DC
6. Using a multimeter set for resistance measurements, place the leads on the ends of the F3 Nano fuse.
The reading should be less than 1Ω.
l
An open F3 fuse may indicate a problem with the Closed-Top Soft Start Circuit Board
7. Using a multimeter set for resistance measurements, place the leads on the ends of the F6 Nano fuse.
The reading should be less than 1Ω.
l
An open F6 fuse may indicate a problem with the Closed-Top Soft Start Circuit Board
8. Using a multimeter set for resistance measurements, place the leads on the ends of the F4 or F5 fuses.
The reading should be around 30-38Ω for either fuse.
l
An open F4 or F5 fuse may indicate a problem with the Closed-Top Soft Start transformers, circuit
board, or fan
Table 4-24 Soft Start Fuse Details
Fuse Amperage Resistance (Ω) Circuit Class Comments
F1 2A Less than 1Ω HV DC to DC - Fast Acting
F2 0.25A Less than 1Ω Transformer Secondary -15V AC to DC-DC - Fast Acting, Nano
F3 1A Less than 1Ω Transformer Secondary - Soft Start Board - Fast Acting, Nano
F4 0.25A 30-38Ω HV AC to Transformer Class CC Slow Blow
F5 0.25A 30-38Ω HV AC to Transformer Class CC Slow Blow
F6 1A Less than 1Ω Transformer Secondary - Soft Start Board - Fast Acting, Nano
9. Troubleshoot to determine the cause of the blown fuse, if necessary replace any fuse that is found to
be defective. Some of the fuses may require the use of needle-nose pliers or forceps to replace them.
Refer to 5.5.2.6 Determining the Cause of Blown Soft Start Fuses (Closed-Top Soft Start Only) on page
272.
10. Install the Soft Start. Refer to Section 4.14.6 Soft Start Installation (Closed-Top) on page 121.
11. Install the top covers. Refer to Section 4.1 Compressor Covers on page 52.
12. Return the compressor back to normal operation.
4.14.3 Soft Start Removal and Installation
This section covers the direct replacement of a Soft Start (i.e., Open-Top Soft Start to Open-Top Soft Start or Closed-
Top Soft Start to Closed Top Soft Start). If you are upgrading to an Open-Top Soft Start from a Closed-Top Soft Start,
be sure to review the spare part instructions that are included in the upgrade kit.
4.14.4 Soft Start Removal (Closed-Top)
1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Remove the Soft Start Temperature Harness. Refer to Figure 4-99 Closed-Top Soft Start J9 Connector on
page 118.
M-SV-001-EN Rev. H-1/23/2023 Page 117 of 294