Hi. My first time on the forum. My Fiat based motorhome has just had the dreaded airbag warning light come on had it checked ecu failure £550 to fix.

[Chevette HS]

I am an engineer so I did some research and it seems to be caused by voltage drop. Useing my engineers brain why can`t you use a voltage stabliser in the circuit so if the voltage drops at start up or any other time the cpu would be protected?

 

[mitzimad]

there is a company that do them if its repairable it may be crash data?

 

[Chevette HS]

Thanks. Yes I have sent it away.

 

[Mikeco]

The voltage drops when the battery goes flat so don’t see how that would work, the cure is to not have a flat battery in the first place.

 

[Jo662]

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[Gromett]

I don't get these failures. As an engineer you must allow for any foreseeable scenarios and protect against them.

A flat battery or a voltage spike are both predictable possibilities so the circuit should protect against them.

I am gobsmacked that this happens so often. Terry had this recently I believe? Not sure how/if he got it resolved in the end but he was given the right old run around on it from memory? Wissel may know something on this as well?

 

[the1andonly]

I am an engineer so I did some research and it seems to be caused by voltage drop. Useing my engineers brain why can`t you use a voltage stabliser in the circuit so if the voltage drops at start up or any other time the cpu would be protected?

Yep i asked the same type of question a while back, even a separate power supply to issolate the cpus from starter events. Poor design.

 

[MisterB]

I am an engineer so I did some research and it seems to be caused by voltage drop. Useing my engineers brain why can`t you use a voltage stabliser in the circuit so if the voltage drops at start up or any other time the cpu would be protected?

Welcome to the house of fun. Are you able to design such an add on yourself and fit it? There may be a market for one? I reckon there are a few people on here with the technical skills to co operate on such a project if it's viable

Hoovie
autorouter
Raul
eddievanbitz

Apologies if I've missed some people off

 

[gus-lopez]

 

[AndyPK]

Welcome from Ciren!

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[Boringfrog]

 

[vzac]

Mine has just been done , luckily for me it was the dealers fault and they repaired the ecu ( new one fitted), it was then ghosting, ( dull lights on seat belt light not going of fully, again part of the dealers issues, they sorted. But did not put a new battery in as its still knacked, changing it in a couple of weeks, fingers crossed it keep enough charge till then. If I could get one of what ever it is to stop it I would have one.

 

[NicM]

The voltage drops when the battery goes flat so don’t see how that would work, the cure is to not have a flat battery in the first place.

Well if you are going to leave your van standing for awhile maybe best to disconnect the battery, best to remove the ground only or remove it and charge it at home.

oh, just to add make sure you have a radio code if you need one!

 

[chatteris]

Is it the battery going flat or trying to start with a low battery or jump leads it does not seem to be a problem if you disconnect battery so surely its trying to start it that's the problem not the battery going flat

 

[Chevette HS]

Hi. Thanks for all the replies. The garage who quoted me the £550 included replacement battery because the reason
the cpu failed was a drop in voltage and they always replace the battery when repairing the cpu.
I had the battery checked and it was 100% Ok so the voltage drop must happen
when you start the engine, that is why I said about putting a voltage stabilizer in the circuit would this work

PS. when not useing the motorhome I have conected to the hookup.

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[SpeedyDux]

I don't get these failures. As an engineer you must allow for any foreseeable scenarios and protect against them.

A flat battery or a voltage spike are both predictable possibilities so the circuit should protect against them.

I am gobsmacked that this happens so often. Terry had this recently I believe? Not sure how/if he got it resolved in the end but he was given the right old run around on it from memory? Wissel may know something on this as well?

Me too. My PVC had been standing for 10 days. 4-year-old starter battery caused the voltage drop even though it started the engine without any apparent issues except the airbag warning light not going out. ECU repaired by CrashData. I also got a new battery.

When the old starter battery still reads 12.7 volts (not under load) that means nothing and the airbag ECU may be at risk. There must be a design problam that FIAT isn't in a hurry to fix. It seems to affect only the minority of MH customers not delivery vans.