June 23, 2018, 03:33:21 PM

Author Topic: Water temp sender and alarmstat sender  (Read 4713 times)

Offline Michael_e

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Water temp sender and alarmstat sender
« on: August 14, 2008, 10:50:52 AM »
More wiring questions. In the pic below there are two water temp senders. They both look almost identical. I'm guessing that one goes to the water temperature gauge and the other goes to an Alarmstat thing. Does it make any differenct which sender is connected to which gauge or alarmstat? And this alarmstat thing, just what does it do? Just make a buzzing sound or does it connect to something that shuts down the engine? The tag on the right hand sender just says Stewart Warner, assembled in Mexico.


1955 GM Scenicrusier, 8V92TA & Allison 754. Totally rewiring all 12v systems and lots of questions.


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Re: Water temp sender and alarmstat sender
« Reply #1 on: August 14, 2008, 10:59:08 AM »
Cant' answer your question....I have a suggestion though. Put your coach with engine/trans. information, year etc. in your profile signature, location helps also. That way any one can glance at it and know what you are working on.  ;D




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Re: Water temp sender and alarmstat sender
« Reply #2 on: August 14, 2008, 11:32:45 AM »
Michael, the sender need to be the same brand as the guage this the problem most of stuff doens't work as in been replaced over the years with mix match parts.I went through the problems for months before I solved it most v types have a alamstat on both sides when working they warn at certian temp and will shut down when over that if wired correctly I know some v engines just have one but I have 2  to protect both sides   good luck
« Last Edit: August 14, 2008, 11:34:41 AM by luvrbus »

Offline buswarrior

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Re: Water temp sender and alarmstat sender
« Reply #3 on: August 14, 2008, 11:46:03 AM »
The engine will only shut down due to high temperature if you have that option, and it is still enabled.

Absolutely, you should have a sensor in both sides of the engine, otherwise one bank could be damaged by a failed thermostat.

Every busnut should check the functioning of the alarm by grounding each one and seeing what the dash does. Don't disconnect the sensors to disable the shut down, you'll get no warning the engine is overheating.

When doing any rad work, changing the alarmstat sensors is the same as changing the thermostats for good preventive maintenance. They are cheap and just do it.

If you experience an overheat on the older mechanical 2 strokes with the shut down enabled, you get no warning, the dash lights, buzzer and shut down happen all together.

If I had a hired driver, the shut down would be enabled, however, since I pay the bills, mine is not enabled, I will decide when and where the engine will shut down, after the dash lights and buzzer sound, not the machine.

After having a real bus do that to you out in the passing lane, busy highway, with a load of people on, you will want the choice too!

happy coaching!

Frozen North, Greater Toronto Area

Offline Michael_e

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Re: Water temp sender and alarmstat sender
« Reply #4 on: August 14, 2008, 12:52:25 PM »
Paul - check now. Hope it helps.

Luvrbus - New gauges & matching senders are on the list. Will be adding senders & gauges for the left side engine. Looking in the corners of the couch for any extra money i can find.

Buswarrior - Lots of food for thought there. Had a lot of the same type of thoughts, caught in slow moving traffic in center lane, shutdown, everyone's mad now. Thought about an over-ride  switch, but getting even more complicated. What about one sender to gauge and second sender to big red warring lite above gauge??

Everyone - I don't want digital gauges on my dash, so what manufacture has the best gauges for our/bus type of application? I mean a gauge face with readings starting around 150-160 and ending around 210-220. I want the most indications between 185 to 205. Most of the gauges i've seen start with readings of about 140 and go up to around 240-250. For most of us, any readings above 210 are unnecessary as the dammage probably has already happened.

Also, does any of the gauge manufactures make an adjustable temperature sending unit? Say, if i wanted a warning light to come on at exactly 198 degrees, do i just request a specific number when ordering a sending unit? I would like one that is adjustable, just to suit my specific configuration.


1955 GM Scenicrusier, 8V92TA & Allison 754. Totally rewiring all 12v systems and lots of questions.

Offline Tim Strommen

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Re: Water temp sender and alarmstat sender
« Reply #5 on: August 15, 2008, 03:05:01 PM »
"...If you experience an overheat on the older mechanical 2 strokes with the shut down enabled, you get no warning, the dash lights, buzzer and shut down happen all together..."

On the Gillig I purchased (which has an MUI 6V-92), the manufacturer had installed a time-delay relay to the shut-down circuit (similar to this one from Tyco).

This way, you get the lights and buzzer and the relay starts counting down (from what-ever delay time interval is programmed).  When the timer expires, the shutdown circuit is activated and the engine dies.  There is also a lacthing one-shot "delay shutdown" button on the dash - which allows you to reset the timer only once if you need a bit more time to get the rig to the side of the road safely under power.

I retained this function, as I have considered loaning my bus to one of my retired uncles (who used to drive school busses).

Fremont, CA
1984 Gillig Phantom 40/102
DD 6V92TA (MUI, 275HP) - Allison HT740
Conversion Progress: 10% (9-years invested, 30 to go :))

Offline Busted Knuckle

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Re: Water temp sender and alarmstat sender
« Reply #6 on: August 15, 2008, 05:53:48 PM »
Alarmstats do come in different temps! On a coach we recently bought, I had several drivers tell me (after the fact), that "unit # 727 would run around 230-240* while pulling hills!"
I was floored, furious and outraged! First off it it's running that dang "hot" why weren't they pulling over and calling me when it happened, instead of telling me 2 weeks later? Second off how come it didn't shut down?
So I pulled it in the shop, and checked out the alrmstat system by shorting out the terminal on top. Yup shut 'er down, which told me that indeed the system was working. But the alarmstats may not be. So I ordered 2 new 210* sending units, and 2 new 170* thermostats. Since the parts wouldn't be in until the next day I took it out on a run to see just what it was doing!

First thing I noticed was the temp gauge only went to 230*, not 240*! Note to self "call and make appointments for Robert & Dave at the eye Dr's!" On the second thought I just called them both and asked when the last time they had their eyes checked was! Robert had no excuse as he'd just gotten new glasses, "but I only wear them for reading!" OK my response was "well put 'm on when reading the gauges!" Dave said "well to be honest, it's been a while!"
Both of them argued with me about what the gauge went up too over the phone, even when I was staring at it! (seems they had had a conversation about it prior to telling me! And Dave took Roberts word for it that it was a 250* gauge like Robert was used to!

Anyway back to the test drive. Anybody who knows me knows I got 2 speeds, wide open or stopped! So I took it down the Purchase Parkway in the #1 mode, and even with the hard pulls just before the Wingo exit all I could get out of it was 210-215* (more than I like, but still better than I'd been told!). Now I did take into consideration that I was empty and they had been loaded! (probably both them & the bus!)

Now I still wasn't satisfied even with it being 100* in the shade & 110 on the heat index, it just wasn't #1) getting close to what they had claimed. #2) why did it still run after 210*? So lets try a different approach! I stopped at the bottom of the steepest long pull and help both pedals on the floor (not a recommended procedure under normal circumstances!) About 2 mins of this and the temp gauge started coming up around 200-205* so I let of the brake and charged up the hill fast and hard as I could on the shoulder, and letting the trans shift out so it would stay "bogged down". OK now by the top of the hill it showed 220*!  I pulled over again and sat with the high idle on, it took it close to 5 Min's to cool of to 180* Now I took off for the shop again and this time it shot right up to about 210 and stayed there!

Well next day my parts in and I changed them. It'd had 180* thermostats, and 220* alarmstat senders! While I changed the parts we flushed the radiators inside and out!
OK back together, and took it for a test drive. Same rte same WOT, hottest it showed was 205* Took it back to the shop and turned over to the clean up guy!

Next morn'n Robert takes off to New Orleans fully loaded! Calls me just after noon and whispers "Bryce this bus keeps shutting down if I run over 68-70mph" I told him "hmmm must be that new governor we put on it!"  LOL! I know it was mean, but he asked for it! He didn't say nothin about it running hot!
A short while later dad comes in the shop laffing and talking on his cell phone! And saying "naw it's those new alarmstats working like they should, we ain't governed ya below the speed limit. Shoot if we was gonna reset a governor on one it'd be Bryce's! Watch and see where yer temp gauge is if it does it again!"

Dad hangs up and looks at me, and says "that was just plain mean to lie to Robert like that! How come ya to do him that way?" I told dad "it made me mad he knew he couldn't run over 68-70 but didn't say a word about temp! So I figured why not have some fun with it!"
So dad says ya know theres somethin still not right about it! I told dad ya I know and I already ordered new trans, and water cooler filters, and would change them when it got home!
Well when it got home we changed both the trans filter and cooler filters. No change! Well OK what next? Since #702 has been pulled from service for major frame issues (whole 'nother story) I thought Hmmm wonder if? Yup sure enough the radiators in # 707 are almost 3" wider that the ones on # 727, hmmmm will they fit? Well let's find out!
Well yes they did fit! And the bus has been running here there and every where the last 2 weeks loaded and in the mntns and heat and never gets over 200*!

So did the larger radiators fix it? Ummm maybe in a way, but really I think that if got the smaller ones rodded out they'd do as good. Also I think that engine is just old and tired and that is a big part of the problem too!

So just because the engine will shut off if ya short the alarmstats out Don't mean they are the right ones or that they are good! It simply means that the system works! Also dad read where MCI has a feature that if the engine shuts down you can depress the starter button and it will override the shut down! (no we ain't tell'n our drivers this!) Also make sure your fuel pressure switch is hooked up & WORKING to prevent the starter from engaging during this!  FWIW ;D  BK  ;D
Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108

;D Keep SMILING it makes people wonder what yer up to! ;D (at least thats what momma always told me! ;D)

Offline H3Jim

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Re: Water temp sender and alarmstat sender
« Reply #7 on: August 21, 2008, 07:17:09 AM »
Thanks BK, LMAO
Jim Stewart
El Cajon, Ca.  (San Diego area)

Travel is more than the seeing of sights, it is a change that goes on, deep  and permanent, in the ideas of living.