Finish Thompson BE-15/15C - Manual (Page 27)

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PROBLEM: LOW VACUUM READINGS AFTER DIVERT (LESS THAN -24” Hg.)
Possible Cause 1: Pump Reservoir is low.
Check whether the Pump Reservoir is low on fluid. This is the most common cause. The reservoir only
needs to be about 1/2” low to diminish coolant flow through the Aspirator. Top off the reservoir with water
or Recycled Glycol until it overflows from the Recycled Glycol Hose.
Possible Cause 2: Vacuum hose leaking or deteriorated.
Two hoses are subjected to the vacuum generated by the Circulation Pump. One is for the Vacuum Gage
and the other transmits the vacuum from the Aspirator to the Divert Solenoid Valve. These hoses should be
inspected for cracks, wear, or weakness periodically. If there are leaks or if the hoses collapse under vacuum,
lower than acceptable vacuum will result. Replace any suspect hoses. Standard automotive reinforced heater
hose can be used.
Possible Cause 3: Debris in Aspirator.
Check for foreign matter lodged in the Aspirator. The Aspirator is a 2” diameter plastic “tube” attached to
the Circulation Pump’s elbow. Restriction of liquid or airflow will cause low vacuum.
1. Drain the Pump Reservoir of all liquid through the petcock on the bottom of the reservoir.
2. Tilt the pump’s motor to the side to expose the Circulation Pump and the Aspirator.
3. Remove the hose that is attached to a barbed hose fitting on the Aspirator.
4. Remove the Aspirator by unthreading it from the pump’s elbow.
5. Clean out the inside taper of the Aspirator. Take care not to damage or distort the shape of the taper.
6. Remove the barbed hose fitting from the side of the Aspirator. Carefully clean out the tiny hole under
the barb fitting—a paper clip works well.
7. Reassemble the Aspirator to the pump’s elbow, reconnect all fittings and hoses, and refill the Pump
Reservoir to the proper level.
Possible Cause 4: Faulty Vacuum Gage.
The Vacuum Gage can show inaccurate vacuum levels if it receives shock or is subject to excessive
moisture or temperature. One sign of problems would be if the gage sticks or does not return to zero.
Liquid can accumulate in the Vacuum Gage’s hose. Remove the hose from the Distillate Piping and allow
any liquid to drain. Early models had the hose connected to the bottom of the cross in the piping. The cross
in the piping should be turned 180° so that the gage’s hose is at the top of the cross to help prevent liquid
from entering into the hose.