CTIS Auto tire inflation system questions

Happy thanksgiving,
i just picked up a 1990 m 929 a2. It has the atis (never had one before) that seemed to work fine on my trip, bringing it back for deleware.
I got to the truck this am to ck it out, drivers side tire was low I started the truck, let it build air pressure but the auto inflation system did nothing to air up the tire. Is there something I'm missing? Do I have to do something to activate the system??
Thanks
BOB

Have you been operating it as the TM says you must?

The ignition, starting and shutdown sequence is very specific for those trucks.

Failure to follow the correct procedure will result in damage.

The air system has to build to 120 psi before the system will engage. If you aren't building 120 psi, it won't work at all. The control module on the shifter tower should have one flashing light. It does take a while to air up a low tire with the ctis system, sometimes up to an hour if the tire is really low. If there are four flashing lights on the control module, press the runflat button and let it build pressure until it kicks over to one flashing light on highway mode, then it will build air from there.

Thanks for the info, i'll get back to it tomorrow
bob

let us/me know it it worked. Mine starts out fine then fours lights flash. I do have one rear tire that will lose air when parked for a while. I manually air it up, but still always wind up with four flashing light. Read and re-read TM's....I'm still confused.

atomoros said:

let us/me know it it worked. Mine starts out fine then fours lights flash. I do have one rear tire that will lose air when parked for a while. I manually air it up, but still always wind up with four flashing light. Read and re-read TM's....I'm still confused.

Click to expand...

Do a search for the Spicer CTIS PDF. It will help you narrow down the problem.

Four flashing lights means you have a tire so low that it needs to start in the runflat setting, or you have a leak in the ctis system, probably either at a wheel valve or a hub seal. The soft air lines between the wheel valve and the valve stem likes to leak and fail as well. Four lights is something you can work with. When you get the four flashing lights, try pressing the runflat mode button and see if it helps. It should air up and then go over to airing up to the highway setting. If it goes back to four flashing lights you have a parts problem.

Does anyone know if the CTIS system can be undone from the tires on a 5 ton. We use it for a brush truck at the fire department and tires leak down often. Can we cap off lines and fill tires up with air compressor to by pass all the lines.

Should be able to unplug the controller and just fill the tire by hand.

Thats what we wanna do but dont want it to back feed to all the other tires. Are they all on one system or each one on their own line. We were using the air system on the truck this morning to fill tires but lost air pressure. But brakes still have pressure.

Be sure to wear one of those skin tight T shirts that have Taco Bell written all over them while doing so.

josh dunigan said:

Thats what we wanna do but dont want it to back feed to all the other tires. Are they all on one system or each one on their own line. We were using the air system on the truck this morning to fill tires but lost air pressure. But brakes still have pressure.

Click to expand...

Each wheel has a wheel valve on it. They don't back feed and in any case they would equalize even if the valve was faulty.

josh dunigan said:

Does anyone know if the CTIS system can be undone from the tires on a 5 ton. We use it for a brush truck at the fire department and tires leak down often. Can we cap off lines and fill tires up with air compressor to by pass all the lines.

Click to expand...

Tires leaking down is almost always the oring needs to replaced between the rims or you have leakage from the wheel valve to the stem hose. You can unscrew the hose going to the tire stem and put a valve core in then inflate the tire and see if it loses air. If it does, then the oring needs to be replaced. If it doesn't then its up stream from there.

Been slowly replacing my o rings. It's fun! BUT... sometimes when I start my A2 and let it build air at an idle the ctis box starts flashing. If I idle it up while it warms up it builds air and then completes it ctis check and corrects tire pressure. If I have a super low tire I hook a compressor to it while warming the truck up so I am not there all day. So try setting the idle up as it airs up. Seems to keep everything working.

There is a new ATIS
It is a good read for the conjecture

https://electrek.co/2018/10/19/tesla-patents-automatic-tire-inflation-system-tesla-semi/

the invention and the prints and patent are in there for all to see.