Took our 8w Foden for test today, the tester picked me up on the bulb out in the hazard switch,no probs i thought i have a spare bulb. Then he sticks the gadget in the tacho and tests the speed limiter,fair play the guy tried 3 times and it went to 96kmh! FAILED. When i was empty i tried her 90kmh no matter how hard i pressed.
After a phone call i take her to a garage that has a computer for Cat engines and within 10 minutes i am out of there and homeward bound the thing is she only does 53mph now and the tacho has just had the 6 year check.
Can any body explain that to me 
Yeah your tyres are shot 
We had to do the same thing with our Alpha 
It passed for 7 years then the 8th time they picked up on it.
I had the same on another truck, but it would only do 52mph 
, no matter what the limiter was set to, turned out to be the ecu as it has a limiter function as well, so it could be that your ecu was set at 90, but the limiter not. So when Mr Vosa stimulated the limiter on the test with a false speed signal, it didn’t cut the engine revs as the ecu wasn’t getting a speed signal , but when you took it away down the road, the ecu was getting a speed signal and was doing the limiters job 
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When you’ve past take it back and get them to up it again, as the tacho and the limiter are two seperate devices, and the limiter can be adjusted within the legal parametres without the need for rolling roads and seals etc.
When they do the static test you often find that the speed at which the limiter cuts in is higher than the speed at which it will hold once in, therefore when these two figures don’t match, it will end up only holding a low speed on the limiter because they have to see it ‘cut in’ at 90 or less.
Similarly, many trucks won’t let go of the limiter until you slow to about 80 kph and you spend your life going to 90 then slowing to 80, coming off the limiter and back up to 90 etc, etc. This is when the cut out speed is set wrong in the tacho head, especially on the Iveco’s
Had the limiter not been working at all, he would not have been able to fail it, just give an advisory about it. Bizarre but true.
pursy:
Took our 8w Foden for test today, the tester picked me up on the bulb out in the hazard switch,no probs i thought i have a spare bulb. Then he sticks the gadget in the tacho and tests the speed limiter,fair play the guy tried 3 times and it went to 96kmh! FAILED. When i was empty i tried her 90kmh no matter how hard i pressed.
After a phone call i take her to a garage that has a computer for Cat engines and within 10 minutes i am out of there and homeward bound the thing is she only does 53mph now and the tacho has just had the 6 year check.
Can any body explain that to me
personally i would’ve argued the toss, the last unit i took for test, had also just been calibrated, tester tried two or three times but couldn’t get any sort of reading from his plug in gizmo, i just stuck the calibration cert under his nose and he had no choice but to pass it!
basically to fail your wagon he’s saying that the calibration equipment used is inaccurate which raises serious issues for the company that carried out the check, the first thing i would’ve done is got that company on the phone while still at the test station and let them argue with the tester as to who’s equipment was right.
Paul.
Don’t waste your time, you will only make it worse. He will only fail it when he has cause, it’s not a personal vendetta. His machine will be registering 92 -95 (which he usually shows you at the time) that it is giving as the cut in speed and is more accurate than your eye and the tacho card. Instead of giving him a hard time which will come back on you, rant at the folk who have done the recalibration and not done the job right.
If it is done properly your trucks limiter will cut in and maintain the limit. If it don’t, don’t pay for a half done job. Lots of places huff and puff when you complain, tell you it’s perfectly right. Then when you tell them what happened at the test they just take the lazy option of reducing the running speed rather than correcting the initial overspeed.
sorry but i totally disagree with that, these people aren’t god if they want to give me a hard time they better be prepared to go a long way with it, because i will be!
after all, at the end of the day they are just mechanics who couldn’t hack it in the real world and i’d bet everything i own on the fact that the testers equipment was inacurate rather than the calibration centers who have to have theirs checked on a regular basis 
I could still get 56 out of it on cruise but only 53 on the throttle pedal, it cost £43 to have the ECU reset and it passed so i will leave it at that,just the standard kick in the nuts we get every day in road transport eh. To my knowledge the 6 year tacho check does not include the speed limiter so its the engine ECU that was at fault and to be fair since the last MOT it had been on the laptop to alter the horse power and make sure she was getting 56 mph so i guess everyone will blame each other and i just pay.
paul b:
sorry but i totally disagree with that, these people aren’t god if they want to give me a hard time they better be prepared to go a long way with it, because i will be!
after all, at the end of the day they are just mechanics who couldn’t hack it in the real world and i’d bet everything i own on the fact that the testers equipment was inacurate rather than the calibration centers who have to have theirs checked on a regular basis
The test centre gear reads the number of pulses and multiplies it by the KPH. Very accurate. The pulse setting is on a sticker in your tacho head typically 7043 or 5137 or some such number. When they rev the motor with the reader plugged in it converts the pulses to kph and sees the number at which it max’s out and will read it in KPH. They will then show you the reading that it stops at. If it goes over 90 they have no choice but to fail it (unless it doesn’t cut in at all). It is reading what the people who calibrate your speedo say is the correct figure and if they do the job right, you have no problems. The trouble is, there are some mechanics out there who don’t do a thorough job and like to try and baffle drivers and owners with the BS because they are tacho trained. I’ve had trucks failed straight out of the tacho centre for exactly this and it was the tacho folk who hadn’t done their job correctly.
Many electronic engines have problems with the readers not working on them and not cutting in even though the limiter is working on the road due to different electronic languages used in ECU’s.
PS. I wouldn’t make that bet if I were you as the test centre equipment is spot on, it only counts and multiplies and could be used by a chimp. The tacho centre kit relies on operator knowledge, skill and the commitment to do a proper job, plus the fact there is usually a queue to get on the rolling road and not enough time in the day. Guess where the corners sometimes get cut.
DoYouMeanMe?:
PS. I wouldn’t make that bet if I were you as the test centre equipment is spot on, it only counts and multiplies and could be used by a chimp.
thats probably just a well, i think some of these clowns in the test centers would strugle to tie their own shoe laces! and they’re supposed to be the cream of the crop, they put the rest out on the road 