Front air conditioning fan not working

[Schnuz]

Hi all,

We've had a '96 Bongo for eighteen months now (and a member since day one) and a couple of weeks ago the fan for the air con in the front stopped working on all settings.

I've worked through the Bongo Fury fact sheets on the subject and ruled out the fan motor as it runs when connected directly to the battery. I'm fairly sure that I've ruled out the transistor module as the problem as I've had it out, taken it apart and measured all the components. The power transistor itself looks fine and measures what I would expect it to with the multi-meter. The diode is still a diode, the resistor measures the correct value and the cap is still intact so I put all that back together.

I've even taken the air con control panel out and opened it up but there is nothing obviously wrong in there either but if one of the chips has blown there would be nothing to see anyway. I can only surmise that something has gone up the swanny with the controlling unit, it would have been nice to find the electrolytic's bulging but no joy there.

Does anyone know if there is anything in the circuit? I have looked on the wiring diagrams and found a possible relay G3-07? If that is a relay does anyone know where it is? I've tried searching the forum but if there is something there I've not entered the correct search criteria.

I hope someone can help as I don't really want to go to the expense of changing the control panel without knowing for certain that it isn't doing its job.

Cheers,

Schnuz.

[g8dhe]

Check to see what happens if you set the fans for Max. 4th position, if the fan runs then that indicates the control transistor has blown as the relay by-passes the transistor, easily replaced https://www.google.co.uk/search?num=100 ... &q=2sd1525 just try to get a convenient pinout. Very few other faults occur on the unit.

[Schnuz]

Check to see what happens if you set the fans for Max. 4th position, if the fan runs then that indicates the control transistor has blown as the relay by-passes the transistor, easily replaced https://www.google.co.uk/search?num=100 ... &q=2sd1525 just try to get a convenient pinout. Very few other faults occur on the unit.

Thanks for the reply but already tried that. The fan does not run in any position. I have tested the power transistor and it is fine. Cheers, Schnuz.

[g8dhe]

In that case the G3-07 relay is a possibility, refer to the diagram on the link below - you will need Flash enabled in your browser

the positions of each devices connectors are shown on the next page of the diagrams so you will find G3-07 on the offside wheel arch.

[Schnuz]

Thanks for the reply, didn't realize that the diagrams showed the positions as well. I shall have a look and get back to you as to the outcome. Cheers, Schnuz.

[Schnuz]

I've had the relay out and it works fine on a bench test. Running out of ideas now, the only thing left seems to be the control panel. Cheers, Schnuz.

[g8dhe]

Does the Fan operate if you manually operate the G3-07 relay (applies power) and the G3-05 (by=passes transistor) together, this will then conform that the actual fan circuit itself is operating, if so then it would appear to be a problem with the controller or its feed to the base of the transistor, which controls the speed of the fan. If you measure the voltage on the base of the transistor you should see a small rise as the power level is increased (ideally its better to measure current than voltage on the base but that is a lot more fiddly to arrange).

[Schnuz]

Thanks for the reply, I'll attempt to manually bypass the relays tomorrow. More difficult than it sounds as they are mounted next to the battery and the battery needs to be removed to get to them. In fact I may video it for the YouTube channel while I'm at it. Cheers, Schnuz.

[g8dhe]

Yup, it helps if you have some crocodile clips on long leads, one end to earth and the other holding a pointed tab to push up the sleeve to earth the correct end of the relay coil - not the Green wire that is the supply

[Schnuz]

Many thanks for the help. After three days of testing and head scratching I finally bottomed the fault, should have realised earlier to be honest . It turned out to be a high resistance fault on Earth point 1 and only found it after bypassing both relay G3-05 and G3-07 and then shorting G3-05 to earth when the fan then began to run. I have done a concise video of the whole process if you think it would be of future use to other bongonaughts : https://youtu.be/zJ-ctfHYFz4 . Cheers, Schnuz

[g8dhe]

I would suggest checking earth point 2 & 3 as well then! Several of the circuits are common between the multiple points so to fail ALL earthing points must have corroded/loosened;

[Schnuz]

Thanks for the reply:

Your right, I should have looked at the diagram a bit more carefully. The heater fan is working again so the initial symptom has been sorted (I was getting a resistance of around 600Ω from the relay to earth) with three in parallel that must mean that all of the earth connections must have been around 1KΩ or more which is not good. Only relying on one decent earth point is not good practice so I will find the other two and give them a dose of cleaning up as well. I was expecting to find a number of ring tongue tags to one bolt but Earth one (and presumably all the others) was a strip of male tags bolted to the bodywork in what looked like a plastic connector strip. I shall go hunting tomorrow and probably do a better video on just the offending earth tags. Cheers, Schnuz.