Webasto HL30 Instruction manual

Workshop Manual—HL30/38/65/95/125 Model Air Heaters

WORKSHOP MANUAL

For Webasto Heater Models

HL30

HL38

HL65

HL95

HL125

Including sections on Operating

Principles, Common Installation

Problems and Faultfinding

Uncontrolled Copy—for reference purposes only

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

Page Number

1. Introduction 3

2. Operating Principles Semi-Automatic Control 4

Fully-Automatic Control 5

Larger Heaters—Differences from HL30 5

Fuel Pump & Fuel Supply 6

Ventilation 6

Glowplug Circuit 6

Thermostatic Operation 6

Exhaust Arrangement 6

3. Service Procedures HL30/38 A. Removing the Heater 7

B. External Components 7/8

C. Opening the Heater 8

D. Splitting motor and heat exchanger 8

E. Heat Exchanger 9

F. Atomiser Assembly 9

G. Fuel Pump 10

H. Motor 11

I. Reassembly 11/12

J. Testing 12

A. Removing the Heater 13

B. External Components 13

C. Opening the Heater 13

D. Splitting motor and heat exchanger 13

E. Heat Exchanger 13

F. Atomiser Assembly 14

G. Fuel Pump 14

H. Motor 15

I. Reassembly 15

J. Testing 16

HL125 16

5. Common Installation

Problems

Ducting 17

Fuel 17

Wiring and Electrics 18

Exhaust System 18

6. Fault Finding 19

4. Service Procedures

HL65/95/125

CONTENTS

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

1. Introduction

The HL series of Webasto Air Heaters were manufactured from the 1960’s and as a result formed a

large proportion of Webasto Heating Installations within the UK at that time. The heaters were solidly

designed using well proven technology, and as such have a reputation for rugged reliability and ser-

viceability. Many of them have lasted in excess of 20 years or more.

Since the mid 1980’s, a new generation of heaters has appeared from Webasto, using new burner

technology and much simpler design. These heaters made the HL30 obsolete and offer many ad-

vantages over older designs.

This manual is intended as a guide for those who have had no experience of the older series heaters,

and should be read as a whole before any service work is undertaken.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

2. Operating Principles

The principle of operation for all heaters is similar. Figures 1, 2 and 3 refer to model HL30, minor

differences with other models are discussed separately.

When the heater is turned on, power is switched to the glowplug (2). This pre-heats the combustion

chamber in it’s vicinity.

After 2-3 minutes pre-heat, power is switched to the main heater motor (78) and simultaneously the

fuel solenoid (10). Since the fuel pump is driven directly by the motor, fuel is now pumped through

the open solenoid, into the fuel pump and injected into the fuel delivery pipe (E, fig 3). From here it is

passed into the rotating atomiser (66) and sprayed past the glowplug into the combustion chamber

(40). Simultaneously, the combustion air fan (64) draws air through the combustion downpipe (20)

and blows it into the combustion chamber to be mixed with the fuel.

This mixture is ignited by the glowplug, and hot exhaust gases pass through the heat exchanger (40)

to be exhausted through the downpipe (22). Simultaneously, the fresh air fan (30) blows air over the

hot heat exchanger and this is discharged as hot heating air into the ductwork. It is to be noted that

combustion (primary) air and fresh (secondary) air cannot mix, and that heating air is therefore free

from fumes.

As combustion becomes established, the temperature inside the heat exchanger rises until the heat

detection thermostat (HD thermostat) (4) contacts close. The glowplug now de-energises and

combustion is self-sustaining and stable.

When the heater is turned off, the solenoid is de-energised and closed, interrupting the fuel supply.

Combustion ceases and the heater cools to the point where the HD thermostat contacts open,

shutting the heater down. The blower motor is energised until this happens.

Semi-Automatic Control (SA Control)

Before approximately 1980, most heaters were supplied with SA Control. Under this system, all

timing sequences are carried out using a clockwork timer switch (12, figs 4 & 5). Closing of the HD

thermostat contacts energises a relay (14, figs 4 & 5) and the green light glows. This circuit also

bypasses switch circuits so that the heater remains running when the switch knob reaches the fuel

heat position. If the HD contacts do not close the heater cuts off at this point. With the heater

running, reduced heat can be selected. In this case, current is switched through different motor

windings.

Overheat protection is provided by a mechanical cut out (7, fig 1 and 5 , figs 4 & 5) which interrupts

the feed to the relay coil so that the heater stops dead. After some minutes, the cut-out should reset

itself.

HL65, HL95 and HL125 SA heaters all use 5 and 7 way Hella caravan type plugs and sockets to

connect heaters to wiring components. Early HL30 SA heaters use the same system, although from

about 1977 onwards a 7 way plastic junction box was used (fig 5). With the exception of this box, SA

wiring components are interchangeable for the entire range.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

2. Operating Principles (ctd)

Fully Automatic Control (FA Control)

FA Heaters first appeared in about 1980 in the UK and for some years there was an FA/SA option.

After two or three years, however, fitting of FA heaters become almost universal.

Under this system, timing and switching is carried out by an electronic control box (11, fig 6). This

box and wiring system is common to all HL FA heaters. Closing the HD contacts results in the

instantaneous de-energising of the glowplug, unlike SA systems where it continues until the time

cycle is completed. Failure to ignite first time results in the start cycle resetting itself after about 3.5

minutes. Thus FA systems will attempt two automatic starts, after which the switch must be reset if

combustion is not established.

Overheat protection is by means of an overheat fuse (9a fig 1, 5 fig 6). Continuity through this fails

when air temperature around it reaches 100°C and this interrupts power to the fuel solenoid, which

closes. The heater therefore shuts down in the normal way. If the heater started first time and

subsequently overheats, the control box will automatically repeat start when the heater stops. It will

obviously not re-ignite however. Overheat fuses are not repairable.

Most of the later HL125 FA heaters still used the red mechanical overheat thermostat, but this is

wired using the third contact so that if it overheats, an electrical in-line fuse (2 amps) blows, cutting

power to the solenoid. This fuse is usually to be found taped to the overheat thermostat leads.

It is not possible to have reduced heat with FA control.

Larger Heaters—Differences from HL30

Solenoid valves, HD thermostats and OH thermostats for all heaters were identical until the HL6511

and HL9511 were introduced in about 1983. At this time, all external wiring components were re-

designed, made smaller, and incorporated beneath a single black external cover. The HL30

remained unchanged. The main modifications were as follows (see fig 7).

1. The solenoid valve was reduced in size and mounted internally as part of the fuel pump (77, fig

8).

2. The electric clutch was replaced with 2 plastic dogs (60, fig 8). See below under “ventilation”.

3. The HD thermostat was reduced in size (6, fig 7) and mounted beneath the cover.

4. The overheat protection system was reduced to a small thermo switch with normally open

contacts. In the overheat conditions these contacts close, shorting and blowing a 2A fuse (7 &

8, fig 7) in line with the solenoid valve, shutting the heater down in the normal way.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

2. Operating Principles (ctd)

Fuel Pump and Fuel Supply

The basic principle of a motor driving an internal piston pump is the same in all heaters. HL30

pumps are however different from those of larger heaters. Any HL30 pump is interchangeable with

any other HL30 pump, even if they are superficially different. Check however that the pump piston

diameter (3.3 mm) is the same. This number is stamped on the pump casing.

All HL65, HL95 and HL125 fuel pumps are physically the same, the only difference being pump

piston diameter, but the above should be noted. Full technical details of all fuel pumps and solenoid

values are given in figs 9 & 10.

Ventilation

Ventilation is an option on all heaters, both SA and FA. On the HL30/38 the motor is energised, and

this also turns the fuel pump although the fuel solenoid remains closed. On larger heaters with

higher pump revolutions a clutch was introduced using a rubber cone and brass cup. This

disengages the pump and motor during ventilation, reducing pump wear. On early HL65 heaters, this

clutch was operated by a mechanical lever, but this was later changed to an electromagnetic clutch

(49/50/51, fig 11—refer to notes above).

Glowplug Circuit

All heaters have the same glowplug and glowplug circuit. The plug is designed to operate at

between 4 and 4.5v. A dropper resistor is therefore required to drop from mains voltage. 12v

droppers have a single element, 24v have a double element. Both types of resistor have a sliding

clamp enabling glowplug voltage adjustment.

Thermostatic Operation

It is not possible to fit a room thermostat for operation on any of the SA heaters. This is only possible

on a FA system, which is wired as shown in fig 6. If the room thermostat is wired as shown,

switching terminals 13 and 14, only one start cycle will be attempted on thermostatic re-start. It, as

can very often be the case, the heater does not start first time, it will therefore not attempt a second

start. Thus the heater will cease operating at a time when it is supposed to be maintaining a constant

temperature.

One solution to this is to bridge terminals 13, 14 and wire the room thermostat in series with the on/

off switch. It will then in effect become a second on/off switch and repeat start will be available if

required.

Exhaust Arrangement

For vehicle applications the majority of heaters are supplied with a downward exhaust, designed to

discharge directly through a floor. A limited length of exhaust ducting can be fitted to this (see p 18).

For marine use, upward exhaust heaters are generally supplied, usually fitting a sealed balanced flue

system.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

3. Service Procedures—HL30/38

This section is intended to give a step by step guide to servicing these heaters. It is recommended

that the section on operating principles should be read prior to commencing any work since this gives

an understanding to the role of the various components. It should be remembered that many heater

faults and problems are due to bad or faulty installations. A more comprehensive discussion of these

problems is given on p. 17.

In general, Webasto heaters have a recommended service interval of about 1000 running hours.

This generally corresponds to 2 seasons work, although exceptionally one year in the case of

applications such as buses and minibuses which are constantly in use. It follows, therefore, that any

heater 2+ years should be overhauled, not merely repaired. This practice is therefore recommended.

Workshop Conditions

You will require the following:

Clean Rags—particularly important for fuel pumps

Degreasant e.g. Jizer, paraffin

Fine abrasive paper e.g. crocus paper NOT emery

Grease—Shell ALVANIA 3 because of it’s heatproof properties

Jointing Compound e.g. Stag

Benches should be clean and swept clear at regular intervals during overhauling procedures. Grit in

motor bearings or pump plates can cause considerable damage. It is recommended that individual

components be overhauled as heaters are stripped down, not as they are built up. Again, this

minimises the amount of dirt present. It is recommended that one complete gasket set be used for

each heater serviced.

A. Removing Heater

1. Disconnect the wiring harness. In the case of a plastic junction box note the positions of

cables beforehand.

2. Disconnect the fuel line from the solenoid valve (12, fig 1) having first turned off the fuel

tap, if fitted.

3. Remove the mounting straps. If these are too corroded, cut through the bolts with a

hacksaw and replace them later.

4. Disconnect ducting and exhaust, if fitted.

5. Remove Heater.

B. External Components

1. Remove the wiring harness.

2. Remove the glowplug (1, fig 2). Replace this if the coil is distorted or there is excessive

carbon build-up

3. Remove the HD thermostat (4, fig 1), replace if bent or damaged.

4. Remove the OH thermostat (if fitted). To test this, hold the end of the probe in a pair of

pliers and twist the body of the thermostat anti-clockwise. You should hear the contacts

click open after about 1/8th of a turn. This distance can be reset by slacking the screws

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

3. Service Procedures—HL30/38 (ctd)

B. External Components (ctd)

4. in the base and resetting the body accordingly. Note that the contacts should reset

themselves when the probe is released. If they do not, replace the thermostat. As

a final check, undo the top securing screw and lift off the red plastic cover. Inspect

the blue wires underneath, if they are in good order reassemble and replace.

5. If the heater has FA control, check continuity through the OH fuse (9a, fig 1). Replace

if necessary.

6. Examine the external fuel hose, particularly the braiding. Replace if frayed, kinked or

corroded.

7. Examine the exhaust and combustion air downpipes, and heat exchanger exhaust stub.

Replace them if they are badly corroded—note that this is usually the case in heaters

with more than 2 years service. If the heat exchanger stub is damaged or badly

corroded the entire heat exchanger should be replaced.

8. Remove the solenoid valve (12, fig 1).

9. Hold the flat mounting of the valve in a vice and undo the solenoid pole-piece and

coil (10, fig 1). Examine the rubber seal on the base of the armature. If this is pitted,

grooved or in any way damaged, replace the whole solenoid armature.

10. Remove the fuel hose (14, fig 1), taking care not to lose the copper end-washer into the

heater.

11. Remove all screws, replace them later if corroded. It is recommended that case screws

be replaced with No 8 pan head stainless self tappers.

C. Opening the Heater

1. Remove the end caps (25, 26, fig 1) by pushing them off with a screwdriver.

2. Upend the heater, fan uppermost, with the exhaust stubs pointing away from you.

Grasp the two edges of the case (27, fig 1) and pull outward and towards you—the

case should slide off.

3. Clean the case and end-cones with degreasant.

D. Splitting Motor and Heat Exchanger

1. Remove the fresh air fan (30, fig 2), clean with degreasant or replace if damaged.

Remove studs (31, fig 2).

2. Tap the end cover (33, fig 2) off the motor case (36, fig 2). Usually, the motor

mounting plate (34, fig 2) sticks to the cover and should be dislodged with a

screwdriver.

3. Withdraw the complete motor/pump assembly and put to one side.

4. Prise apart the motor case (36, fig 2) and heat exchanger (40, fig 2). Clean and

degrease the motor case, replacing the gasket (35, fig 2).

5. Replace the sealing string on the end of the motor case, cementing it in place

with jointing compound.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

3. Service Procedures—HL30/38 (ctd)

E. Heat Exchanger

1. De-carbon. This is best achieved with either a pressure washer, or hot soapy water

and vigorous shaking. It is not sufficient merely to poke about inside with a screwdriver.

Note that excessive carbon deposits should not occur—see p. 18.

2. Examine the heat exchanger carefully, particularly the welds between the inner and

outer jacket and the exhaust stub. The complete assembly should be replaced if there are

any signs of perforations since these will allow fumes into the heating air. It is pointless

trying to weld any holes since they will only re-appear somewhere else.

3. Examine the backwall (41, fig 2). If the fins are corroded or flaking, it should be replaced.

In any case it should be removed and re-sealed in position. To do this, place a small

extractor inside with the lugs facing outwards so that they locate inside the inner flange of

the backwall. Hold the heat exchanger suspended by the extractor and tap the brackets

(A, fig 2) with a small hammer. The backwall should slide out, but if excessive force is

required, then the backwall is obviously well sealed and should be left alone.

4. If the backwall is extracted or replaced, smear jointing component around the outer face,

position correctly (line up the glowplug hole with the appropriate hole in the heat

exchanger) and tap home so that the top of the backwall is flush with the top of the heat

exchanger. Re-check the alignment of holes, if necessary by inserting a glowplug.

F. Atomiser Assembly

1. Return to the motor/pump assembly. Hold the combustion air fan (64, fig 3) firmly and

undo the retaining nut (61, fig 3).

2. Remove the nut, washer (62, fig 3), atomiser cup and fan. Examine these components for

flaking and corrosion, clean or replace as necessary.

3. Remove the atomiser (66, fig 3) and round washers (65, fig 3). Note that these washers

are included in the gasket set and should be replaced routinely. The atomiser is one

of the most important parts of the heater and a number of installation faults can be

detected by examining it;

Blocked Atomiser Pipes are caused by continual running at low voltage (see p.18).

Missing Pipes are caused by overheating, which melts the brazing holding the pipes on

(see p.17).

4. Examine the inside of the atomiser. Build up of a deposit indicates dirt in the fuel.

Thoroughly clean the atomiser and pipes. If a pipe is missing, replace the whole

atomiser.

5. Remove the back plate (69, fig 3) by removing the two holding screws.

6. Examine the two plates—if they are loose, replace the washers (70, fig 3) which are

included in the gasket set. These should be tapped home into the recesses in plate 69

and plate 75 tapped into position.

7. Remove the roll—pin above the motor shaft washers, but first note the distance between

the atomiser pipes and dished washer (fig 12). Remove all washers.

8. Undo the two pump retaining screws (A, fig 3) and slide the pump off the motor shaft.

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Workshop Manual—HL30/38/65/95/125 Model Air Heaters

3. Service Procedures—HL30/38 (ctd)

G. Fuel Pump

There are three types of fuel pump (fig 13), all superficially different, but procedures are

basically the same for them all.

1. Remove the inspection plate (b, fig 3) and clean it. It is recommended that this plate

being aluminium is inscribed with the date of the service for future reference.

2. If a separate bubble separator is fitted, push it out from behind, using a suitable drift.

Clean it, check that all pipes are clear, and replace the “o” rings. Sediment in the

bubble separator is an indication of dirty fuel. Later fuel pumps (fig 13c) have a single

pipe embedded in the pump casting. Check that this is not loose. If it is, thoroughly

clean and re-araldite it back into position.

3. Replace the bubble separator, ensuring that the inner flat is adjacent to the pump

casting hole. Tap it home with a suitable drift, taking care not to bend or damage

the pipes.

4. Remove the screws (1 fig 13b—nuts in pump type A). Remove the pump top cover,

clean inside.

5. Remove the pump spring which should always be replaced.

6. Remove the pump outer gasket and pump piston assembly. It is essential that this

assembly and the plate on which it sits are in good order, and the following checks should

be done:-

i) Push the piston fully down, place a thumb over the hole in the assembly body,

and pull the piston completely out. You should hear a healthy “plop” as the

piston is withdrawn. If you don’t, replace it.

ii) Examine the pump plate for wear. In particular, examine the area between the

fuel inlet and outlet holes. If this is scored, the pump plate must be replaced.

iii) Hold the end of the eccentric pump shaft and rock it to-and-fro. If any play

at all is detected, the pump shaft bush and oil seal should be replaced.

If at this stage all the above checks are in order, then the pump may be reassembled. Be

sure to add some fresh grease and replace pump outer gasket and spring. If any of the

above checks reveal wear, proceed as follows:

7. Remove the pump shaft circlip.

8. Remove the pump drive wheel and retaining woodruff key (roll pin in early heaters).

Examine the wheel for wear and replace if necessary.

9. Push the pump shaft out and examine it for wear. If there is any noticeable step where

the shaft meets the bush, replace both.

10. Place a No. 8 screw into the bush, and using this as a drift, knock out the bush with

a punch. Insert the new bush in the same way. Note that the bush always wears more

than the shaft, and once it has been replaced the shaft can be inserted to check for wear.

Any play at this stage must be due to shaft wear, which should therefore be replaced.

11. Using a suitable drift, knock out the pump plate oil seal and insert the new one, ensuring

that it is replaced in the correct orientation.

12. Replace the pump inner gasket.

13. The pump can now be reassembled. When the shaft and drive wheel are assembled,

replace the pump piston assembly and turn the wheel by hand to ensure freedom of

movement. A little light machine oil should be placed in the bush before replacing the

shaft. Ensure that the new spring locates correctly in the pump cap recess. The

access chamber should be half-filled with grease.

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