How to Determine the Best Solution to Fix Hot Caravan Brakes
Key Features
- Universal Application: Works for all 10-inch and 12-inch electric brake brands.
- Multi-Axle Compatibility: Applicable to single, tandem, and tri-axle configurations.
- Dual-System Diagnosis: Covers both electrical voltage drops and mechanical overloading.
- Preventive Maintenance: Establishes a baseline for daily safety checks during tours.
- Proven Engineering Logic: Developed using professional engineering and electrical expertise.
Specifications & Equipment Required
To perform this diagnostic procedure safely and accurately, ensure you carry the following test equipment in your caravan safety kit:
| Required Tool | Application / Purpose |
|---|---|
| Volt Meter | Measures the exact voltage delivery at the backing plates. |
| Ammeter | Verifies current draw across the electromagnets. |
| Temperature Meter (Infrared Gun) | Identifies thermal variance between wheel hubs. |
| Screw Driver | For accessing terminal blocks, plugs, and backing plates. |
| Electrical Tape | For insulating re-spliced or newly run wiring. |
Diagnostic Procedure
- Daily Thermal Check: After a day on the road, measure the temperature of each wheel hub using your temperature gun.
- Analyse Variance: All wheel hub temperatures must be within 5% of each other.
- Isolate Hot Wheels: If one wheel is significantly hotter, suspect the cold wheel on that same axle is not working.
- Measure Voltage: Run the tow vehicle engine and manually operate the in-cab brake controller. Measure voltage directly at both backing plates on the affected axle.
- Avoid Breakaway Tests: Do not pull the breakaway pin during this test; doing so introduces a false voltage reading and bypasses potential vehicle plug faults (e.g., a dirty 7-pin plug pin).
- Apply the Fix: If the cold wheel shows low voltage, run a secondary parallel cable across the axle. Connect it to the existing wires to increase the copper’s cross-sectional area, eliminate voltage drop, and redistribute the braking load evenly.
Frequently Asked Questions
Procedures
- After each day on the road, measure your wheel hub temperature with the temperature gun.
- All temperatures should be within 5% of each other for each wheel.
Result of temperature check.
- One hot wheel, measure the voltage on both backing plates on the same axle as the hot wheel.
- Measure the voltage by running the car and operating the brake controller manually. Do not pull the breakaway pin as this will give you a false voltage reading. For example, a dirty pin on a 7-pin plug may be the culprit, so you need the voltage coming directly from your brake controller.
- The cold wheel may have low voltage and may not be working at all
Solution
Run another cable across the axle and connect the two cables to increase the copper’s cross-sectional area. This procedure removes voltage loss from the cold wheel, causing the lazy cold wheel to start braking. At the same time, it will dramatically reduce the braking load on the hot wheel.
Electric Brake Magnets
We find that magnets are not usually the cause of hot brakes.
However, they do wear out and require replacement, as they are perishable items.
Driving a caravan on corrugated roads with a highway magnet will quickly destroy the magnet and the magnet arm.
In these cases, the backing plate should be replaced.
A range of good-quality backing plates can be found here
Breakaway Switch
If you have been driving through rain or river crossings, it is possible that water has entered your breakaway switch, causing your brake to engage without your knowledge. Solution: disconnect the breakaway switch and wait for it to dry before reconnection.
Electric Park Brake
Check that the park brake has been disengaged before driving. Often, a forgotten park brake is easily overwhelmed by some of our large 4WD power plants, with the driver not noticing the caravan is braking. However, a quick walk-around will identify the smell of burning brakes.
Bearings
The first indicator of failed bearings is black grease.
Black carbon is released from the bearing coating once wear accelerates. The bearing must be immediately replaced.
Some drums come with cups inserted. Make sure the bearing you are inserting is the same brand as the cup that has been inserted. Mixing brands is not good and will shorten the maintenance cycle on your bearings.
If the bearings are burnt and scoured beyond repair, if the axle is marked, then the axle needs replacing.
The axle has a bearing shadow caused by grease getting under the bearing. The axle is slightly undersized and will cause excessive bearing wear.
Bearing shadows can reduce a bearing’s life by up to 50%.
What is the tolerance between a good bearing journal and a bad bearing journal? Axles machined overseas can have tolerances exceeding 0.05mm, which is enough to classify the axle as not suitable for read use. For example, a bearing ID of 22mm should have a tolerance of 0.02mm – 0.04mm at 21.98mm.
Brake Shoes
Checked voltages; all are within 5%, so now we are onto the brake shoes.
With your screwdriver, remove the brake shoes from both backing plates to remove braking on the entire axle. Test Braking.
It would be unusual for the brae shoes on one side to be misaligned.
A range of brake shoes can be found here
Polarised Drum
A polarised drum is rare; the solution is to replace the drum.
A drum becomes polarised when a magnet is scraped constantly, and over time, absorbs the same polarity as the magnet.
A quick solution is to reverse the polarity by swapping the wires; however, upon closer inspection, you will find that the magnet surface is completely damaged and will not allow 100% braking efficiency.
A good range of High-Quality Brake Magnets is available here.
Government Safety & Towing Regulations
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