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max49 · 09-03-2007, 05:30 PM

Sry, this is long but trying expain what my WH did.
I pulled the Blazer for the first time and within 15 minutes we were pulling the EB 7% Eisenhour tunnel mtn. I've pulled my boat , which probably weighs about the same many times and the temp gauge stays welded right in the middle.
But this time was labor Day and half way up was a traffic jam. I was in 1st gear about 4600 RPM, normal for this pull when traffic came to a halt.
I was stopped quite a bit and put it in neutral , then we'd pull up a bit and stop again. I think within 5 minutes of this, I noticed my temp gauge moving up where it's never been before. After another 5 or 10 min. of this it was up 1 line from the red. The engine seemed like it was running fine. I even had confidence in it and turned it off in the highway, and restarted it to see if the gauge would go back to normal.
It started right up but the gauge went back where it was. I kept putzing, stop and go for maybe 3 or 5 more minutes and the gauge just about touched the red. The engine seemed fine and I started to think this may be an electrical glitch. But then the LCD read 'check engine coolant'. I pulled to the shoulder with a few miles of traffic behind me and 40 miles of traffic jam ahead of me.
We were 10 or 11,000 ft up so it was'nt hot, probably in the 60's.
I turned the engine off for less than 5 min.
Traffic started moving a little so I fired her up, fine and merged in . we w started moving about 15 MPH and I was pleasantly amazed to watch the gauge moving back down toward the middle. WE still had a long ways to go up this 7% slope and came to a stop several more times. The gauge tried to creep up , one line above the middle as long as I could keep moving about, even 10 or 15mph , it was fine, and was fine for next 80 miles or so til I got home.
When it was overheating, or at least the gauge said it was, the roaring fans never once came on. I thought maybe they were malfunctioning but the eventually came on later when the gauge was in the middle, as usual.
I guess my question is, has this happened to any one else?
What tell the fans to kick on and what are the parameters to tell them to turn on?
Is there a relatively easy way to put a manual switch in to turn the fans on for a stuation like this?
Does anyone know where I would tie this switch in?
Since the engine was running fine, do you think this could have been an electrical glitch, and the engine was fine?
There were a lot of dead cars ,trucks, big and little and even one MH pulled to the side with their hoods open.
Other than this, I think the MH did pretty good pulling this 4000+ lb toad for the first time . Oh yea, the MH has a hard time starting off , pulling the toad up a 7% grade at 11,000+ ft elevation.

max49 · 09-03-2007, 05:30 PM

Sry, this is long but trying expain what my WH did.
I pulled the Blazer for the first time and within 15 minutes we were pulling the EB 7% Eisenhour tunnel mtn. I've pulled my boat , which probably weighs about the same many times and the temp gauge stays welded right in the middle.
But this time was labor Day and half way up was a traffic jam. I was in 1st gear about 4600 RPM, normal for this pull when traffic came to a halt.
I was stopped quite a bit and put it in neutral , then we'd pull up a bit and stop again. I think within 5 minutes of this, I noticed my temp gauge moving up where it's never been before. After another 5 or 10 min. of this it was up 1 line from the red. The engine seemed like it was running fine. I even had confidence in it and turned it off in the highway, and restarted it to see if the gauge would go back to normal.
It started right up but the gauge went back where it was. I kept putzing, stop and go for maybe 3 or 5 more minutes and the gauge just about touched the red. The engine seemed fine and I started to think this may be an electrical glitch. But then the LCD read 'check engine coolant'. I pulled to the shoulder with a few miles of traffic behind me and 40 miles of traffic jam ahead of me.
We were 10 or 11,000 ft up so it was'nt hot, probably in the 60's.
I turned the engine off for less than 5 min.
Traffic started moving a little so I fired her up, fine and merged in . we w started moving about 15 MPH and I was pleasantly amazed to watch the gauge moving back down toward the middle. WE still had a long ways to go up this 7% slope and came to a stop several more times. The gauge tried to creep up , one line above the middle as long as I could keep moving about, even 10 or 15mph , it was fine, and was fine for next 80 miles or so til I got home.
When it was overheating, or at least the gauge said it was, the roaring fans never once came on. I thought maybe they were malfunctioning but the eventually came on later when the gauge was in the middle, as usual.
I guess my question is, has this happened to any one else?
What tell the fans to kick on and what are the parameters to tell them to turn on?
Is there a relatively easy way to put a manual switch in to turn the fans on for a stuation like this?
Does anyone know where I would tie this switch in?
Since the engine was running fine, do you think this could have been an electrical glitch, and the engine was fine?
There were a lot of dead cars ,trucks, big and little and even one MH pulled to the side with their hoods open.
Other than this, I think the MH did pretty good pulling this 4000+ lb toad for the first time . Oh yea, the MH has a hard time starting off , pulling the toad up a 7% grade at 11,000+ ft elevation.

HuskyJack · 09-03-2007, 06:44 PM

Max, you have two different fans on the motorhome. The main fan uses a bi metal coil that when the engine gets to a preset temp the coil locks up the fan and you hear the roar from the fan. The second set of fans are the two that can be seen on the front of the radiator, these fans come on when you run the air conditioning..
You can put a switch on these fans that would allow you to turm them on when you want.. Check on the drivers side of the radiator for a thermo switch with two wires,one wire comes from the fan unit and the 2nd wire goes to ground. Install a switch on your dash, one wire to ground and the second wire goes to the fan side of the thermo switch. ... HOpe this helps..
Jack

FrontRangeRVer · 09-04-2007, 02:49 AM

Since I live at altitude and drive up Ute Pass alot, I would say that stop and go traffic at that altitude does cause your engine to heat up abnormally. While I haven't had my temp gauge nearly that high, the air is much thinner here and the engine is really gasping for air.

I am surprised that your clutch fan wasn't running though....

DriVer · 09-04-2007, 05:50 AM

About putting in a switch in the auxiliary fan circuit .... "What IF" the switch is off when the PCM calls for it and you some how forgot to turn the switch "ON"! I would forget about manually switching the fans.

I believe FRRVer was making a pretty good point. Now my question is how does altitude affect boiling point in a pressurized cooling system? Does not boiling point increase past 212?, perhaps this comes into consideration when the cool pack just isn't getting enough moving air through the grill work.

Max stated that the temperature returned to normal after he was moving 10 to 15 mph. Pulling uphill on a 7% grade with a 4K load in stop and go traffic might challenge all but the largest cooling systems.

I too am curious why the main fan didn't clutch up given that the command center posted an over heat message.

Tom N · 09-04-2007, 06:29 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DriVer:
About putting in a switch in the auxiliary fan circuit .... "What IF" the switch is off when the PCM calls for it and you some how forgot to turn the switch "ON"! I would forget about manually switching the fans.
</div></BLOCKQUOTE>

The thermo switch would still turn on the fans. The axillary installed switch is installed in parallel with the thermo switch.

-Tom

Bob (WA0MQE) · 09-04-2007, 07:09 AM

I thought the two-electric cooling fans were for the transmission. I've heard mine come on and off even when I'm not running the air conditioning. It typically was during long pulls up long hills, mountain passes, etc.

Photog · 09-04-2007, 07:49 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DriVer:

Now my question is how does altitude affect boiling point in a pressurized cooling system? Does not boiling point increase past 212?, perhaps this comes into consideration when the cool pack just isn't getting enough moving air through the grill work.
</div></BLOCKQUOTE>

Since the cooling system is closed and under pressure, I don't think the internal boiling point changes.

I do think the lack of air causes the engine to work harder and that causes more heat.

Bill

max49 · 09-04-2007, 05:35 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by HuskyJack:
Max, you have two different fans on the motorhome. The main fan uses a bi metal coil that when the engine gets to a preset temp the coil locks up the fan and you hear the roar from the fan. The second set of fans are the two that can be seen on the front of the radiator, these fans come on when you run the air conditioning..
You can put a switch on these fans that would allow you to turm them on when you want.. Check on the drivers side of the radiator for a thermo switch with two wires,one wire comes from the fan unit and the 2nd wire goes to ground. Install a switch on your dash, one wire to ground and the second wire goes to the fan side of the thermo switch. ... HOpe this helps..
Jack </div></BLOCKQUOTE>

Thankyou ,Husky Jack
This seems like a great idea if it doesnt mess up the 'auto on' feature on the fan. I have'nt looked at the MH to see if I can find the wires you are talking about yet, but which fan or fans would this switch control? The 2 little fans in the front or the big one that roars? My roaring fan comes on much more often if I have the AC on but I did'nt want to turn the AC on when it was already running hot, but it seems it would have helped if the fan kicked on.
If I tap into those 2 wires on the fan side, can I just splice in the wire between the thermo switch and the fan or do I have to connect to the thermal switch?
Will it hurt any thing to have 13 volts backing up to the thermal switch?
I don't know why the fans did'nt come on either but alto I've pulled this and many other tough passes, even with the boat, I've never had to stop 1/2 way up it before and normaly after I go up, I go right back down.
The engine was singing along at 46/4800 RPM , then I had to come to a quick stop, but it did'nt take much brake effort. My MH has never had to do that before.
Even tho I've only burnt one SP wire, the manual fan switch seems like a good idea for a few reasons.
Thanks again guys.

HuskyJack · 09-04-2007, 05:53 PM

Max, the new switch would control the two small fans in front of the radiator which are turned on by a thermo switch screwed into the radiator. If the radiator reaches a preset temp, the switch connects the wires together making a circuit to ground so the fans run.
There is no voltage on these wires, only a ground. Trace both wires to see where they go, one will be to ground and the other back to the fans, splice into the fan wire, run a wire to your new switch and then run another wire from the new switch to ground.
Before you splice into the wire you can check it by using a volt meter to be sure there is not voltage.. THen you use a wire connected to a pin or something sharp, connect the other end of this wire to ground and probe each wire, the fans should come on when you connect ground to the fan wire.
Hope this helps.
Jack

MikeT · 09-04-2007, 05:55 PM

I believe the electric fans not only operate with A/C on, they are also thermostatically operated and can run even if the engine is off. If this is the case, perhaps the thermo switch is defective.

DriVer · 09-04-2007, 05:57 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bob (WA0MQE):
I thought the two-electric cooling fans were for the transmission. I've heard mine come on and off even when I'm not running the air conditioning. It typically was during long pulls up long hills, mountain passes, etc. </div></BLOCKQUOTE>The fans are auxiliary cooling fans and they can come on at any time when they are needed. The fans direct air flow through the cool pack so everything behind the fans would be a beneficiary including the transmission.

The 2 electric fans are primarily present for support of the air conditioning system.

This summer I shut off my ignition switch got out of my seat and hooked up Roxy to take her for a walk. By the time I got outside the auxiliary fans were still running and shut off a short time after ward. This was "after" I gave the motorhome a 2 to 3 minute cool down idle.

It appears that the cooling fan circuit is continuously energized. I do like MikeT's idea about ruling out a bad or defective thermal switch rather than initially installing a manual switch.

John-D · 09-05-2007, 03:29 AM

About putting a switch on for the aux fans....
The question was What is the computer calls for fans and the switch is off.. if I am reading the OP properly then the fans come on.

The current t-stat can be looked upon as a switch

---/----- (as best I can draw in ASCII

The suggested mod is this

--|---/---|---
|---/---|

I hope this comes out right, as you can see the two switches are in parallel, either switch on the fan runs, both off it does not.

As for the OP... The engine cooling system relies in part on movement of the motor home down the road to create some of the air flow. This is common in large engines and without the movement of the coach.. .There was not enough air flow to keep the engine cool

Bob (WA0MQE) · 09-05-2007, 04:33 AM

Not quite correct Tom, If you look at the CD Shop Manual W22-L18 Schematics, at Sheet #031, Page 1 of 1 it shows the Aux Fan Relay, which turns the fans on/off, being directly controlled by the Powertrain Control Module.

If you dig a little deeper, you will see there is a Temperature Sensing Thermo Switch, who's output goes to the Powertrain Control Module.

You are correct, the fans are controlled by the switch, but through the computer (Powertrain Control Module)