Posted on: March 30, 2009

Originally printed 9/78

Many Alpine and Tiger owners have expressed concern over inefficient heater ­defrosters. This problem is not so much one of design but of attention to details. Please note that none of the heater cores, except Tigers from #38200001 (Mark IA), are sealed in any way to the body at the blower air-intake aperture. Although this seal is shown for Tiger Mark IA on, it is often found to be missing. To obtain maximum efficiency from your system, the following items should be checked and adjusted, repaired or replaced as necessary:

    1. Heater cores that have been subjected to radiator sealers, Stop Leak, Barrs Leak, and others generally become partially blocked across the bottom tubes. Flush or replace as needed.
    2. Check the water control valve actuating cable. Be sure that the valve is opening fully. Adjust as necessary. See illustration.
Fig 1
  1. Install cold weather (winter) thermostat. Minimum 185 F.
  2. Seal the heater core to the blower air-intake aperture if your vehicle is not so fitted. Any medium dense foam or rubber strips or cut sheet (weather strip or typewriter pad) will work very well. The jute padding strip between the heater core cover and heater core side tanks must be left in place to prevent the holding stays on the under side of the cover from wearing a hole in the top of the core side tanks.
  3. Inspect defroster hoses for tight fit (taped on) and freedom from kinks or crushed spots that would restrict flow.
  4. Inspect all firewall plugs and seals. Where these are missing, duct (racer) tape works well if the proper plugs are not available. Also, a small strip of body sealer will help if the steering column seal is loose.
  5. Inspect convertible (hood) top/hard-top to door glass for proper fit (seal). Adjust or replace as necessary.
  6. Check the heater blower motor current draw. It should be less than ten amps.

Once having completed the preceding checklist, the heating system will be operating at its maximum efficiency.

As an added note, all Alpines and Tigers prior to series V Alpine and Mark IA Tiger have small vents between the crash pad and the dash face at the extreme outer edges. These should be sealed during cold weather. In addition, remove blower motor and inspect the inlet screen. Leaves and pine needles often collect there and block the air now.

Comments (4)

I would appreciate a diagram of connections from the blower switch to the blower. Unable to get off-low and fast. Only getting fast and off. Please help if you can. Thank you, Richard M.

Richard,

As I recall, low speed is achieved by dropping the voltage across a resistor. Assuming negative ground, one switch terminal goes to +12 and the other two should be from the switch to both sides of the resistor. The switch wiring is shown pictorially in the shop manual and here: http://www.rootes1725cc.info/wsm145/wsm_r/r_24.htm If the resistor is bad (open) you will only get off / high, but a loose / missing connection will do the same thing.

Joe

Thank you Joe. The 2 black wires from the motor, one is a ground and the other on the blower is disconnected with a bare end. Where does this wire get connected?

Hi I have the tools to make the heater blower unit and the heater rad, and the the tools to make heater water valves for all sunbeam Alpine’s,
The heater parts are in stock.
Regards Ashley Hinton

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