5 replies to this topic

[Jamieboy]

I have a 1994 1275 HIF38 carb with factory 3AS immobiliser. The battery and alternator are recent, battery is charged. All fuses have tested continuity and are the correct value, battery 12V supply and earths are all good.

 

I had the following circuits randomly and simultaneously fail:

• Left and right indicators, hazards & dash warning lights
• Fuel and temp gauges
• Battery and oil pressure warning lights
• Starter solenoid feed (from ignition)
• Interior light
• Washer pump

 

What still works:

• Side, dipped and full beam lights (and full beam indicator)
• Wiper motor
• Reverse lights
• Brake lights
• Horn
• Brake test circuit switch indicator
• Heated rear window and switch indicator
• Foglight

 

I immediately suspected the immobiliser as it has control over a number of the failed but it still has the ability to flash the indicators and the hazard switch warning light and dash lights for indicators. I bypassed the immobiliser lockout of the starter solenoid relay and am able to crank the car. If the key is in position "2" (the position where normally the battery/oil pressure warning lights are on) and I use this bypass, the car cranks and starts as normal.

 

When I did some further investigating today, I randomly got ignition lights when the immobiliser was disconnected, but still no indicators. Afterwards, when I reconnected the immobiliser, I got ignition lights and managed to crank the car once. I rulled-out the immobiliser at this stage.

 

 

So the question is does anyone know the loom well enough to suggest if all the failed subsystems have a common power supply and, if so, where is it likely to have failed? I have a multimeter and Haynes manual, but there doesn't seem to be a definitive circuit diagram for my model, which appears to follow elements of the "88-on carb model" schematic, but also the immobiliser seems to only be mentioned in the "fuel injected models" section as "Relay Module"!

 

 

 

Any help would be gratefully received.

 

Jamieboy

[minidaves]

check the power cables of the starter motor and iirc some had fused links in these cables

[Jamieboy]

check the power cables of the starter motor and iirc some had fused links in these cables

 

Thanks buddy, I will check this out but I'm thinking that it's likely an intermittent open circuit to explain the random behaviour.

[Jamieboy]

After a long winter hiatus, I have finally got round to working on the Mini again. I have now solved the most critial of my electrical problems. As a foreword, if you have a late HIF38 Mayfair, or something similar, with factory 3AS immobiliser, you need to refer to section 12.39->12.46, which is misleadingly labelled as being for "fuel injected models". 

 

Working from diagram 20 on page 12.40 I started from the battery (checking ground for low-ohm continuity to the body), then to the front of the car to the starter (including grounding), then the fuses. It turns out that the inline fuse (labelled as '7' on one side in the diagram), which lives under the scuttle behind the air filter housing, was the problem, the one with white wire in, white wire out. The fuse was intact and I had previously checked its continuity many times, the problem was the spring-loaded seat which touches against the fuse had oxidised just enough on the output side so as to give very high resistance. I found this by pushing my meter probe into the assembled holder with the fuse in and the ignition on and got ~13V in, ~4.8V out!

A cleaning of the contact saw that rise to match the input side and now I have restored:

• Fuel and temp gauge operation.
• Battery and oil pressure warning lights
• Starter solenoid feed (from ignition)

I will continue tomorrow to go over the whole loom, marking each section as I test it and hope to find the cause(s) of the other problems.

[Jamieboy]

All problems are now fixed and all were as a result of oxidation of the sprung seats of in-line fuse holder(s) behind the carb/under the scuttle. Cleaning these (and any contamination of the fuses) fixed all my electrical problems.

[Mini Manannán]

Good work, persistence pays off!!