Author Topic: adjusting a telma retarder...  (Read 5159 times)

Offline 86neoplan

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adjusting a telma retarder...
« on: May 28, 2006, 06:36:57 AM »
I have just found out that my 26' neoplan is equipped with a telma retarder. The thing must be shut off or something, cause when i take my foot off the accelerator, i dont feel anything.

where is the off/on or adjustments on these? I would love for that to work considering it is a hybrid brake system anyhow. it is air/hyd brakes.

go figure..


Proud single custodial dad to a wonderful 14 year old son, Owner of a 1986 Neoplan 26' transit Bus AN408, Great weekender...Lots of work to come on this bus, can't wait to get her done! 8.2L with a Allison AT545...

Offline TomC

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Re: adjusting a telma retarder...
« Reply #1 on: May 28, 2006, 09:25:47 AM »
There are several ways the telma works.  I just delivered two big trucks with it.  One was a straight truck with flat bed that the telma worked in conjunction with the service brakes all the time.  Plus there is a 5 position switch on the dash for manual operation.  On the other truck since it is a 3 axle tractor, the operation of the Telma was only with the 5 position switch on the dash so the driver had complete control over it.  One of the complaints I had to Fontaine that did the installation (a Freightliner vendor that is approved for custom installations at assembly time.  The truck is fully assembled then taken down the street to Fontaine for the "factory" installation of the Telma.  By doing this it is fully factory backed) was that unlike a Jake brake, the Telma did not have an on/off switch.  Neither did it have a micro switch on the gas pedal so the Telma would kick off when you depressed the gas pedal.  So you could accelerate with the 5 position switch on the dash still on (although it has very obvious red lights that progressively come on in relation to the amount of braking).
Shawn- what has probably happened is a fuse or sensor has blown.  Get the model number of the Telma and I can see if I can get any technical information for you.  What I would suggest would be to possibly repair the automatic operation with the brake pedal.  But I have a feeling that might be a bit pricey (I don't know this for sure).  What I would do would be to install the 5 position manual switch on the dash and call it a day with that.  Then you'll be in 100% control of the Telma.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline boogiethecat

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Re: adjusting a telma retarder...
« Reply #2 on: May 28, 2006, 09:42:55 AM »
Tom has it right although if you can get it to work *properly* with your brake pedal, it will make your brakes last up to 10 times longer because it is capable of doing 80%+ of all your braking needs.

I would definitely put a switch on the gas pedal to disable it as Tom said.  If you forget to turn the manual switch off after going down a grade, it'll eat all your horsepower in a flash.  I'd go one step further and put in a manual switch to totally disable it.  Driving in ice and snow I don't think I'd want it working as it's 1-2-3-4 resolution doesn't have enough finesse to safely drive in those conditions.

To figure out what you have, follow the wires.  The Telma unit itself should have a big fat wire from it's frame to ground.  This needs to be intact as it can carry as much as 180 amps depending on your Telma model. 
Then there are 4 heavy wires going from the Telma to a toaster-sized relay box.  There should be another big fat wire coming directly from the battery to that box, providing it with 12 volts.  Inside that box are four relays... sometimes the contacts go bad although it'd be rare for all 4 to fail.  All you have to do is manually push them one by one and if it's not too bright where you're working, you should be able to see the contacts spark as you manually actuate them.  If you get that far, the Telma and relays are all working ok and it's what controls the relays that's not working.  There aren't many fuses in the system (mine has none at all)
but there may be one somewhere.
That box may be the end of it if you have  a simple system, or you may have one that connects into your ABS braking system if you have one... then there'd be another box that does the ABS and control interface.
If you have one of those and it's failed, you could replace/repair it, or just dump it, rewire and go with the 5 position manual switch and the relay box only for a simple system...

Here are two Telma manuals- one is for parts and the other has a "simple system" schematic... maybe this can help out a bit....

One thing to know, however you actuate the thing, Telma (and I) recommend that you make SURE to never leave it on when stopped, like at a traffic light or in a traffic jam situation.  The thing will work really well but it relies on it's fans spinning to keep it cool.  Two things need to be kept cool- the rotors (which won't make any heat if stopped) and the coils, which get really hot if the thing isn't spinning.  According to Telma you can burn one up if left in the "on / stopped" mode for very long at all, especially if it'a already hot from coming off a long grade....
« Last Edit: May 28, 2006, 09:48:12 AM by boogiethecat »
1962 Crown
San Diego, Ca