increasing multimeter fuse rating

[ruston]

Well the easiest way is to leave them in the car , take the terminals and cables off , one probe of a resistance tester on the tip of the plug the other to the earthed body and read the resistance , if there is none they are goosed . the readings should all be about the same if they are healthy.
This method has limits as the tips can be burned away.
Ths correct way is to take them out-sometimes a pain , and do the same test but between the the terminal tip and the plug body.

 

[Specialist]

Resistance testing is always a good first step, but my preferred way is always a Current clamp or an old fashioned Wilkson Automotive Volts / Amps tester.

A used ac / DC clamp can often be had for around £20 - 25
The Wilkson around £50 - 60 depending on model & this will directly read either 60 or 100 amps dc, But needs to be placed in series with the load.

Please don't increase the fuse rating in your meter, the only thing that will happen is you'll see a puff of smoke as your meter goes Ouch & dies.

 

[ruston]

Yes if you have a clamp meter it is half the battle.
The older type though the tips used to burn away or be fouled up , although working to a degree did not do the job properly. If they were easy to get at my first choice was to take them out.

 

[Specialist]

My first choice nowadays is called a Roy (Well abused car mechanic, only 2 owners from new)

 

[ruston]

I'm called Roy too then lol.
I am going out this morning on a love job on bespoke electric steps on a taxi.
The harness is about 20 singles wires and they are all the same colour . They do have lettered ID on them but it is about every four inches . You've guessed it, it's in harness tape or flexible conduit in a place where Hitler couldn't find it. Plus there is a flat floor and seats built on top of the access I need.

 

[Specialist]

Some of the old trucks & machines I've worked on had what we used to fondly call Henry wiring.
Any colour as long as it's Black (Harks back to the old model T ford).
If it still had the markers at each harness junction or end etc, you had a fighting chance.
If not, then hope the local Vicar wasn't passing cause the air would be blue .

Good luck with the job buddy, hope it's an easy one.
A cheap tone tracer often comes in handy.

 

[ruston]

Well I'm hoping it has just blown the supply fuse when the step failed . the mechanic has fitted a new step , but there is no power to the extend/retract switch for either side.
The mechanism is linked to the parking brake so that they will only operate when the brake is on as they slide out from under the sills.
They usually fail because of corrosion though , they are after market wiring seperated from the ECU so it could get involved lol.

 

[Specialist]

Sounds like a bit of an involved setup. Just what you need for a Sunday morning, hope he's got plenty of tea & biccies on the go
Do me a favour & let me know the outcome buddy, always interested in faults on things I wouldn't normally come across.

 

[ruston]

Yes I will.
It also has a system that when the footbrake is on the back doors lock to stop the the unsavoury types doing a runner. It also has an intercom and seperate heater and blower , and cab lighting on the same system. The drivers cab is seperated by a security partition so they are a real pain to work on . Most of the access is under the centre consol or under the seats.
On the plus side there are full workshop facilities , hoists and all the supplies I will need , and a 'bait room ' lol.
Sunday is the best day to do it, less time pressure.

 

[Specialist]

Thanks mate. Certainly sounds shall we say, an interesting set up.

 

[ruston]

Well , to be fair it does not give much bother , there are four of them convertions to wheelchair adapted cabs . The steps seem to be the only stumbling block ( ) as they are under the sills and get all the salt and crap . They have limit switches that suffer badly as does the 'window wiper ' type mechanisim.

 

[Specialist]

Strange how limit switches are always fitted in the worst places, looks like time to get down & dirty mate

 

[ruston]

Yep, going to the bacon sarny van now, then off to crack it lol.

 

[Specialist]

Hi ruston: Just wondering how you got on with the taxi job buddy ?.

 

[ruston]

Well it's sorted. Combination of a few faults that caused the failure .
On the off side the harness from the detachable plug to the unit had been suffering from water ingress to a tube clamped to the top of the unit underneath the sill. This contained two resistors and two caps. One of the resistors ends had corroded and although making contact , was just fortuitous.
On the common signal wire are two caps linked to each microswitch switching wire respectively ; the cap connection was corroded through , this was not making a contact to one switch at all, so that unit was not working at all. An attempt to fix it by replacing the micro switches had failed. The nearside worked , so it was left for another day.

The nearside eventually failed too , this was a combination of a faulty harness plug and a duff micro switch, the switches were replaced (not by me), but it still did not work.
The control unit was getting the signal that the step was deployed and the buzzer could not be stopped sounding with the handbrake on or off , so someone had pulled the two multiplugs out of the unit so the whole system was dead.
No one thought to tell me where the control unit was, or that it had been disconnected. It is in the cab partition hidden behind the drivers seat, with the seat backed right up against it .