webasto_Troubleshooting_Tree.pdf

Thermo Top - Troubleshooting Tree

07-15-2002

CAUTION

Troubleshooting requires comprehensive knowledge about the structure and theory of operation of the Thermo

Top heater. Troubleshooting and repairs may only be performed by Webasto trained and certified, professionals.

Functional Description - Thermo Top

Switch On

When operating via the "instant heat" button on the 24 hour digital timer, or when the timer reaches the preset

starting time, the flame indicator on the timer display illuminates. This activates the heater, glow pin, combustion

air fan and the circulation pump. After 30 seconds the fuel pump starts and the combustion air fan operation is

suspended for 3 seconds. Subsequently, the combustion air fan speed is increased in two ramps within 56 seconds to

part load operation. After a stabilization phase (constant speed) of 15 seconds the combustion air fan speed is again

increased in a ramp within 50 seconds to full load. After reaching full load, the glow pin is deactivated and the

combustion air fan operation is increased. During the next 45 seconds and during normal heater operation, the glow

pin functions as a flame sensor to monitor the flame condition. Once the start-up and stabilization periods have been

completed the heater begins the automatically controlled heating operation. In case of a no-flame condition during

start-up or a flameout during normal combustion operation, the heater will go into a “shut-down upon malfunction”

state with a run-down of the combustion air fan.

Heating Operation

When the coolant reaches temperature the heater switches to the energy saving part load operation. A rise in coolant

temperature above the upper threshold causes the heater to enter a control idle period. The circulation pump and the

operation indicator light remain on during control idle. After cool-down of the coolant, the heater resumes full load

operation. Another rise in coolant temperature above the upper threshold causes the heater to enter the control idle

period again. A drop in the coolant temperature during part load operation due to an increased demand in heat will

cause the heater to switch to full load operation.

Switch Off

When turning the heater off by pushing the "instant heat" button on the 24 hour digital timer or after the preset

timer cycle elapses, the indicator on timer panel extinguishes, combustion terminates and the shutdown (after-run)

phase commences. The circulation pump and the combustion air fan continue operation during the shutdown phase

to cool the heater down and will be automatically switched off afterwards. The duration time and the combustion air

fan speed during the shutdown phase depend on the heater operating condition at the time the heater is turned off.

Shut-down time duration is normally 180 seconds (3 minutes) when deactivated in full load operation and 100 seconds

(1.6 minutes) when deactivated in part load operation.

Dependent on the software variant implemented in the control unit there might be time duration deviations from those

shut-down periods as stated.

Webasto Product North America, Inc. • 3333 John Conley Drive • Lapeer, Michigan 48446

For Technical Assistance In USA Call: (800) 555-4518 • In Canada Call: (800) 667-8900

Visit us on the Web at: www.webasto.us

Org. 07/2002

Thermo Top - Troubleshooting Tree

(Continued from page 1)

Page 2

ATTENTION!

Troubleshooting is normally limited to the isolation of defective components and provides information on defective

wiring and connections.

The following possible causes for trouble have not been taken into consideration and must always be excluded as

a possible cause for malfunctions:

• power supply to heater is less than 10.5 volts at main power connections (charge batteries and perform load test).

See wiring diagram on page 5 for reference to power connections.

• blown fuses.

• corrosion on battery terminals for heater, electrical wiring, connections and fuses.

• loose contacts or connectors, wrong crimping on connectors.

• ensure heater and components have been correctly installed following all pertaining installation instructions.

Troubleshooting Steps

After 3 consecutive unsuccessful startup attempts, the heater will lock itself out from any further start attempts. The

heater may also enter the lockout mode after experiencing an overheat condition. Before troubleshooting the heater,

ensure heater is not in the “Lockout” mode by performing the following reset procedure:

1. Ensure timer or switch is in the off position. Turn timer or switch to the on position. Remove fuse F2 (20 Amp),

refer to wiring diagram on page 5 for identification. Reinsert after 5 seconds.

2. Cycle timer or switch off and then back on once more. Remove fuse F2 once again and reinsert after 5

seconds. Heater should attempt to start in 10 seconds after inserting fuse. Coolant temperature must be below

the lower threshold before heater will attempt to start.

Did heater attempt to start?

(Combustion fan running)

Check for 12V on signal at

heater connector X1, pin 3

with timer/switch on.

Repair or replace harness,

connectors, fuses, or

timer/switch accordingly.

Check for 12V at heater

connector X2, pin 1.

Repair or replace harness,

connectors, connections or

fuses accordingly.

Check for ground at heater

connector X2, pin 2.

Repair or replace harness,

connectors or connections

accordingly.

YES

Continued on page 3

Replace Thermo Top heater.

Webasto Product North America, Inc. • 3333 John Conley Drive • Lapeer, Michigan 48446

For Technical Assistance In USA Call: (800) 555-4518 • In Canada Call: (800) 667-8900

Visit us on the Web at: www.webasto.us

Org. 07/2002

Thermo Top - Troubleshooting Tree

(Continued from page 2)

Page 3

Is combustion air intake free

from damage and

obstructions?

Repair/replace air intake

tube or remove obstruction

accordingly.

Is combustion exhaust pipe

free from damage and

obstructions?

Repair/replace exhaust pipe

or remove obstruction

accordingly.

Does fuel pump operate

(clicking) during start-up

cycle approx. 30 sec. after

switching on?

Connect test light

to fuel pump leads

(leads connected

normally).

Does the light blink

slowly after 30 sec.

of switching the

heater on?

Is fuel pump

harness free of

damage?

Repair or

replace harness

accordingly.

YES

Replace heater.

Reconnect fuel pump and

turn heater on. After 30

sec. lightly tap fuel pump.

Does fuel pump begin to

operate (Click).

Replace fuel pump.

System should resume

normal operation. Pump

may have been stuck due to

dirt in fuel or long periods

of no operation.

Disconnect fuel line from

heater fuel inlet. Turn

heater on and observe fuel

expelled from fuel line.

Does the pump expel fuel

approximately 12 inches?

(1-2 inches if pump is

equipped with a damper)?

Are fuel lines and fuel filter

free of obstructions? Is

there air in the lines? Are

fuel lines free of damage,

pinched sections, or leaks?

Are the fuel line clamps

tight? Is there sufficient

fuel in the fuel tank?

Replace fuel filter.

Repair/replace damaged

and obstructed fuel lines.

Tighten loose fuel line

clamps. Purge air from

lines. Fill fuel tank with

sufficient fuel to reach fuel

standpipe inlet.

Continued on page 4

Replace fuel pump.

Webasto Product North America, Inc. • 3333 John Conley Drive • Lapeer, Michigan 48446

For Technical Assistance In USA Call: (800) 555-4518 • In Canada Call: (800) 667-8900

Visit us on the Web at: www.webasto.us

Org. 07/2002

Thermo Top - Troubleshooting Tree

(Continued from page 3)

Page 4

CAUTION

Allow heater to cool down before disassembly of coolant circulating pump. Allow heater to cool down before

attempting to restart.

Does coolant pump operate

when heater is running (can

feel or hear pump running)?

Remove center

plastic cover from

heater. Disconnect

coolant pump

connector X5.

Apply 12V directly

to the pump (+ to

black and – to

brown). Does

pump operate?

Remove

coolant pump

and 4 cover

screws. Clean

pump

accordingly.

Assemble and

reconnect

pump. Does

pump now

operate?

Replace coolant

circulating

pump.

YES

Replace heater.

Problem

resolved. Test

run heater.

Does heater start and

operate normally?

Check coolant hoses for

obstructions, kinked hoses,

low coolant level and

proper hose routing, etc.

Heater is operating

normally. Possible

intermittent problem.

Should problem reoccur,

rerun through this

troubleshooting tree.

Webasto Product North America, Inc. • 3333 John Conley Drive • Lapeer, Michigan 48446

For Technical Assistance In USA Call: (800) 555-4518 • In Canada Call: (800) 667-8900

Visit us on the Web at: www.webasto.us

Org. 07/2002

Thermo Top - Wiring Diagram

Page 5

RED

RED (Power supply to heater)

RED

BLACK (ON Signal to heater)

Battery

RED

–

MAIN

POWER

BROWN

Fuel

Pump

Fan

Motor

Coolant

Pump

RED

BROWN

Additional wiring diagrams are available. Refer to the Thermo Top Operation/Installation manual.

PC Diagnostics

A PC Diagnostics kit is available that allows for more thorough testing and troubleshooting of the heater and its

components beyond the scope discussed in this document. Other functions such as reading values while the heater

is in operation and printing out of fault codes is also available (user supplied computer and printer required).

Order PC Diagnostics Kit under P/N 92542F and the required adapter under P/N 92566A.

Webasto Product North America, Inc. • 3333 John Conley Drive • Lapeer, Michigan 48446

For Technical Assistance In USA Call: (800) 555-4518 • In Canada Call: (800) 667-8900

Visit us on the Web at: www.webasto.us

Org. 07/2002

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