Meet Bumble-bee – My own car
It’s a 2004 ’53’ Fiat Punto Active Sport with the 1.2 8v engine with 75k miles on the clock
What is the complaint
Driving along the interior fan would randomly cut out and back in when on speed 3 only
However speeds 1, 2 and 4 worked perfectly fine with no issues
Previous Work
This vehicle has had issues with the interior fans before, where speeds 1-3 failed to work;
speed 4 did work, a classic case of a resistor pack failure, however this wasn’t the actual case. The electrical connector overheated badly causing it to melt destroying the main earth pin on the resistor pack connecter, a donor clip and loom had to be used to remove the damage
Diagnosis Time
I nipped onto Auto-data and found a wiring diagram for the interior fans and highlighted what I knew was working okay, leaving 1 track un-highlighted for been the cause
Since the fans were able to work, there was power been received – Which isn’t visible on that page, I could also confirm the blower was working okay, the switch, resistor pack and wiring and earthing for speeds 1,2 and 4(bypass of resistor pack) were all okay, leaving just 1 of 3 causes
A faulty Switch causing a temporary break in the circuit when on speed 3
the resistor pack was breaking down internally
The wiring from the switch the resistor pack
When the fan did cut out – a firm tap around the glove-box lid make the fans spark back into life for a short while, till another shock caused it to cut out again
This left me believing a poor connection would be the cause of the fault.
Since the switch is tucking inside the dashboard and was harder to reach – the resistor pack connector would be inspected first and was pulled free
Immediately there was an obvious problem; the connector was showing signs of overheating again, affecting the main wire that feeds the fan for speed 3.
There was discoloration of the wire near the connector
A concentrated heat spot in-line with the pin
a small patch of insulation had melted exposing bare copper cores
Usually excessive resistance causes extra heat, so I decided to trace the circuit from the motor through the switch back to the connector with a multimeter set to Auto Ohms to see the condition internally.
For speeds 1 and 2, the reading was less than 5ohms from point A to the corresponding number on the resistor pack
However when the switch was on 3; there was a huge increase in resistance, over 45ohms.
The prolonged heat caused damage to the connector, causing an increase in resistance
The Fix
The only way to fix this problem would be to replace the connector, so a visit to a local scrap yard to locate a healthy looking plug and extra loom
carefully using cocktail sticks, the pins were released from both connectors, and rebuilt into the donor connector. Using the spare wire and spade terminal from the donor, the old connection was cut out – joined together, soldered and heat-shrinked
While disassembling the old connector, the plastic melted the locking latch for the wire, causing the poor connection, reducing the contact between pins increasing the heat due to the load, also brown scorch marks can also be seen in the connector due to excessive heat, a continual loop till the connection would have gone open circuit or a potential fire could have started
A quick check to ensure all speeds worked correctly and a final resistance check showed that the resistance had dropped back down to 4.7ohms, a 90% difference then before
Ensuring the connectors were fully secured into place, the wiring was tucked back under the dash as it was originally.
Tapping around the glove box area while on speed 3, ensured it did no longer cut out before clearing the foot-well of the old connections and wiring.
bbautorepairs 