CTIS Overspeed alarm with no restart

Thank you to everyone for the invaluable information in helping me get a 1993 Stewart Stevenson up and running from a charging issue. Unfortunately, the time has come to pick everyone's brain yet again. Sitrep: While parked, I start the SS and it alarms out for CTIS Overspeed. It continues to build air pressure for the brakes, but no air runs through the CTIS to apply air to the tires. The CTIS controller is a black box (apparently there are 2 different ones?) that is set for highway. Not that it matters as it alarms at start up. So, I then go and shut it off and restart it. Surprise number 2, it will not even try. It's acting like there is a lock out on the starter. Any thoughts??

Disconnect the CTIS controller. It doesn’t need to be plugged in for the vehicle to operate. If still having the problem start looking past the CTIS. Most likely a grounding or electrical problem. Mine had a loose wire on the starter solenoid.

Keith Knight said:

Disconnect the CTIS controller. It doesn’t need to be plugged in for the vehicle to operate. If still having the problem start looking past the CTIS. Most likely a grounding or electrical problem. Mine had a loose wire on the starter solenoid.

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Will it still inflate tires without the controller?

No, most likely the CTIS system is not working and you can figure that out later.
You can air the tires up like any other tire, there are valve stems. Holding air is another question.

The truck won’t crank/start? CTIS has nothing to do with the start circuit.. CTIS senses the same pulse per mile signal that the speedometer uses. It’s pea brain compares that to a lookup table that has a different value for each tire pressure selected and will warn the operator if he is driving too fast on low tires. If it is just coming on without driving, probably the controller.

There are several things that will keep the controller from starting a check and fill cycle it needs to see a pressure sw close on the wet tank, which happens around 117psi. Are your pri/sec brake gauges reaching 125 like they are supposed to?

no connection to the start circuit whatsoever, so your no crank is another issue.

what in the power panel goes click when you turn on the ignition(should be K11 and K24 and the oil idiot light should light in the panel)?

does your trans control show N N?

What goes click when you push the start button(should be K1 in the panel and the aux start solenoid on the drivers frame rail, as well as the starter)?

any double or multiple relay clicking/chatter?

here is the entire A0 start circuit on one page to aid your troubleshooting.

Great to hear from you again Ronmar. Anyway lots of questions and I have lots of answers so here we go.

Correct, after the "CTIS Overspeed' Alarm which was going off since start up, I knew was a load of crap because I was parked and haven't moved the vehicle at all. I haven't had the time yet to see is if K-52 somehow killed power further down the line to prevent engine damage.

I can hear at least one relay come alive. Judging by the alarm going off at start up, I believe it is K-11. K-24, I am not sure of. I push the start button there is bupkis. No relays clicking, no chatter, nothing. Its like the lights are on but nobody's home. This is why I think the CTIS may have tripped a lockout of some kind somewhere.

Trans control does show N N, and air brakes are engaged.

Ctis has no such control or any interface with the start ckt. They both draw ign power but thru different breakers/fuses…

when you turn on ign, K02 provides ign power to everything via fuses.
Some of that power passes thru the vim neutral relay and goes to the start relay K01 pin 86, that's the + side of the start enable ckt.

ign power also feeds K11 and 24 and the low oil pressure sw completes the ckt to ground to energize them and the oil light.

K24 connects K01 to the start button which provides a path to ground to energize the start relay k1. No click in the dash when you push the button something is missing from the two halves of the in cab part of the clt..

pull k01 and ign on you should see 24v on its socket pin 86.

With ign still on, if you measure resistance to ground from K01 pin 85, you should see high resistance that goes low when you push the start button.

these checks will point you toward where to look next…

You should also be able to jump K01 pin 30-87 and the engine should crank…

Rick_bagby said:

Will it still inflate tires without the controller?

Click to expand...

No, but it shouldn't need to.
With the controller disconnected, the tire pressure remains at it's current psi indefinitely.

If it's not holding psi, you have a leak(s).

Ideally, you do NOT want the CTIS system compensating for leaks.

You say there is an "alarm" going off like it's an audible alarm? That's the low air pressure buzzer or troop alarm if this is a cargo with the troop alarm intact.

Has NOTHING to do with the CTIS.

And the alarm / CTIS issues are not related to a no-crank.

You have three distinct issues.

1. Low air alarm.

2. CTIS issues? If you have less than 95 psi in the wet tank the CTIS won't even try to operate so my guess is it's just flashing whatever terrain light it's waiting for system pressure to do a pressure check.

3. No crank.

These are entirely different issues, each with different solutions if they are even broken.

You also could just have dead batteries. The low air alarm will sound if you accidentally manage to reverse the battery polarity or feed power into the ground plane. Don't ask how I know this - it involves smoked electronics and was NOT a battery terminal/connection mistake but I'll leave it at that.

GeneralDisorder said:

You say there is an "alarm" going off like it's an audible alarm? That's the low air pressure buzzer or troop alarm if this is a cargo with the troop alarm intact.

Has NOTHING to do with the CTIS.

And the alarm / CTIS issues are not related to a no-crank.

You have three distinct issues.

1. Low air alarm.

2. CTIS issues? If you have less than 95 psi in the wet tank the CTIS won't even try to operate so my guess is it's just flashing whatever terrain light it's waiting for system pressure to do a pressure check.

3. No crank.

These are entirely different issues, each with different solutions if they are even broken.

You also could just have dead batteries. The low air alarm will sound if you accidentally manage to reverse the battery polarity or feed power into the ground plane. Don't ask how I know this - it involves smoked electronics and was NOT a battery terminal/connection mistake but I'll leave it at that.

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Definitely not a battery issue. They are fully charged and brand new batteries. Long story behind that one as well. I have created a 110 circuit with a 4 bank battery charger with desulphonator. I took out the NATO charging connector, and added a 110 male waterproof connector. Basically when I plug it in, it kills all the batteries. The charger then comes on and charges all the batteries at once as 12 volt batteries and maintains them. Unplugging it, restores the battery connections and brings back the 12 and 24 volt power as needed. Actually kind of proud of myself. Batteries were $80 each from Rural king (Regular car batteries with 750CCa each) and about $100 for the rest of the supplies including charger.

I am going to disconnect the CTIS controller and see if that helps since it is alarming out anyways.
The low air alarm is still present when system pressure reaches 100+ PSI. That is a new developemnt and the dash reads CTIS overspeed. I have no doubt there may be multiple issues again, but the CTIS was my major concern. Until I found it would not restart. I will try it again this weekend.

Third From Texas said:

No, but it shouldn't need to.
With the controller disconnected, the tire pressure remains at it's current psi indefinitely.

If it's not holding psi, you have a leak(s).

Ideally, you do NOT want the CTIS system compensating for leaks.

Click to expand...

Ideally, I think you are correct. Long term CTIS shouldn't be counted on for leaks. I haven't really looked at the tires to see if they did or did not have valve stems. Originally, I thought that is what the CTIS was for. Well, a year and half later, I have definitely learned a lot and can sit back and laugh at myself and think, "God what a NOOB" I was.LOL.

I don't think the CTIS is capable of operating the low air buzzer...... That's my point. If you have an audible alarm above 95 psi, and a CTIS overspeed warning light with the truck not even running let alone not traveling over 62 mph AND you have a no-crank situation then in my estimation you have a SERIOUS electrical problem. Probably a polarity reversal of some kind. That will defeat the circuit protection diodes in many vehicle warning lamp circuits, and I know from direct experience that it will make the warning buzzer alarm continuously if there is power on the ground plane.

The symptoms you give concern me greatly in terms of what could have happened to you electronics. Proceed with UTMOST caution.

yep, CTIS won't power the buzzer.

On the A0 the primary and secondary air pressure senders also contain the low air pressure alarm switches that drive the buzzer. I think they go on at 89PSI, so should clear the buzzer when the pressure goes slightly above that.

the pressure senders are right at eye level on the drivers side when you open the drivers door to climb in(forward of your left shin when seated in the drivers seat.

Ronmar said:

yep, CTIS won't power the buzzer.

On the A0 the primary and secondary air pressure senders also contain the low air pressure alarm switches that drive the buzzer. I think they go on at 89PSI, so should clear the buzzer when the pressure goes slightly above that.

the pressure senders are right at eye level on the drivers side when you open the drivers door to climb in(forward of your left shin when seated in the drivers seat.

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I'm still concerned with the sudden lack of cranking and the CTIS overspeed lamp with the truck not running is just WEIRD.

If the tanks are low then the alarm is normal but OP is talking like he's never heard the alarm buzzer before so all of this is confusing from my vantage point here at 10,000 feet.

GeneralDisorder said:

I'm still concerned with the sudden lack of cranking and the CTIS overspeed lamp with the truck not running is just WEIRD.

If the tanks are low then the alarm is normal but OP is talking like he's never heard the alarm buzzer before so all of this is confusing from my vantage point here at 10,000 feet.

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It is confusing, and I don't like coincidences! but like any elephant it still has to be eaten one bite at a time

I made the electrical changes last year in August. It has been started and running once a week since then. Monday is when this issue popped up and had no idea where to even begin to look. Once again you guys are found to be a tremendous fountain of knowledge. The audible alarm has always come on at start up until it hit like 90 PSI. This is the first time it didn't. System pressure was over 100. It took about 3 minutes from start up for the alarm to silence. When I hit 5 minutes, I knew something was wrong. I will start by removing the CTIS controller and double checking tire air pressure. Those will be my first 2 bites of this "elephant". Great analogy by the way Ronmar. I love it. I am so going to be stealing that one..

thank Dave Ramsey

how high do your air pressure gauges get?

If they are not making it to 125, something is wrong, bad pressure sensor, air leak(most likely), mis adjusted governor or compressor problem... i would recommend introducing another way to measure air pressure, like screwing a gauge directly into one of the brake tanks to confirm the dash gauges are reading properly...

charging the system with an external air source makes it a lot easier to check most of the system for leaks without the cat purring...