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Other temp switch options for volvo fan swap?


cstarbard

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Hey guys,

I just recently did the Volvo fan swap onto my 96 2.3. Overall I'm very happy with it, but I'm wondering what other options there are for temperature switches besides the BMW and VW switches listed in the tech section here, and here's why:

For my 2.3 I thought the lower temperature BMW switch with 180 degree and 215 degree settings made sense, which it does. But: I had a scanner hooked up to my truck to check at what temperature the switch would kick the low speed of the fan on and off, and I found that the fan came on at 170 degrees and wouldn't shut off until 106 degrees. I tested this half a dozen times with the same results.

170 degrees is a totally sensible point at which to kick the fan on, but I was surprised that it took cooling down to 106 degrees to shut it off. This isn't necessarily a problem, I was just hoping the fan would shut off much sooner than that. At this point, once low speed kicks on, the fan essentially stays on for the remainder of my time driving the truck for the day unless I shut it off for a long time before driving again.

Are there other options for temperature switches that would shut low speed off at a higher temperature? It just seems unnecessary to have it running that long.

I can fabricate housings for any temp switch so the thread specs, physical size of the switch really don't matter to me.

Also, I'd like to add a note as an FYI to others looking to do this swap, who need a temperature switch housing for the BMW switch. The switch has 14x1.5 threads; if you don't want to run adapters or can't find any temp switch housing to start with, you can make a housing on the cheap using some common parts store parts. For mine, I found Advance Auto carries tons of lug nuts with 14x1.5 thread, so I drilled a hole in a 1.5" exhaust connector tube and welded the lug nut to the tube, thus making a temp switch housing with correct thread. It fit right in my radiator hose no problem. Just be sure if you do this to weld barbs of some kind on the exhaust pipe... ask me how I know. :)) Nothing makes a fun time like the housing blasting out of your radiator hose. Even if you can't weld, I imagine paying to have it done would be cheap.

Thanks in advance. Chris
 
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RonD

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I think that temp switch is broken, usually its a 15-20 deg swing between on(grounded) and off(ungrounded)

Not sure on description of how it was mounted to detect coolant temp?

Sender/switch should be in the coolant flow otherwise it will hold higher temp longer
Could the sender/switch be holding a higher temp than the coolant once fan comes on?

Are you checking temp at the sender/switch or at upper rad hose?
 
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Right now I am using an Imperial adjustable controller that I got for about $30. It is running my half of a Ford Taurus fan nicely in my mom's Mustang.
 

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I originally had the higher rated BMW switch for mine and had it installed in the upper radiator hose. That didn't work well for me. I think the upper hose stays hot after the thermostat closes and makes the fan run a long time. I then moved that switch to the lower hose and it worked much better. A few weeks ago, I switched to the BMW switch with the lower setpoints, mounted in the lower hose. I think it's working great now. But I haven't driven it much lately.

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generally i run it in the neck or the heater line close to the neck as possible.


it throws a relay that throws the big relays on my intech fans.

i have had a few nice controllers but they always get fawked up. the one i posted above has mixed results...but since it wont directly run my fans i think it might be ok...

lately its been a cavalier switch because i been using gm wiring piggies with my diesel....

when i run eec stuff it was a mustang switch or the summit switch generally with a manual over ride on a three way toggle.... but its currently an alligator clip:D


Part #: TFS27 Line: BWD



you can get 2 that style but from kem parts shipped from rock auto for less then 10 bux.
 

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I'm running the Volvo fan on the dual core 4.0 radiator with my 5.0 and the BMW sensor mounted in the thermostat housing on the Explorer intake.I don't have one of those fancy infrared temp tools, but it always runs cool. I also set up the fan so it only runs with the ignition in the ON position.
 

cstarbard

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Thanks a ton to all you for the helpful info! Looks like I have some research to do from your suggestions.

Ron, I also was afraid that the temperature switch might be faulty, but it is brand new. Still possible it's broken though, of course.

I have my temp switch mounted in the upper radiator hose, and I did have that fear that it might not be the best place for it. Sounds like you guys have had better luck with the switch mounted in other locations. And to clarify I do have the BMW switch with the lower temperature switch point values.

When I was reading the temperature to determine when the switch would kick on and shut off low speed for the fan, I was using an OBDII scanner, so I don't honestly know where the scanner gets the temperature values from. The values I posted above were read from that OBDII scanner, which I suppose could read inaccurately as well.

I am suspicious of the switch itself, because I have noticed that sometimes I can make it almost 40 minutes before the fan kicks on, and sometimes it only takes 15 minutes. I live in a very remote area and I always take the same route to and from work so my driving is consistent enough that I thought this was weird.

I have bypassed the switch several times and put power to the relays manually to check that high speed, low speed both work correctly without the switch, and they do every time.

I will look at your other temperature switch options and consider moving the temperature switch.

So Ron, it sounds like you are suggesting that the fan switch be mounted in or near the coolant overflow? And Bobby you are suggesting running the temp switch near the thermostat housing or in a nearby heater hose? I do have a heater hose close to the thermostat neck. And I see someone else suggested putting it in the lower radiator hose. In theory is there any particular place I could put the switch to ensure that it would read the temperature most accurately and consistently? I was afraid that putting it in the upper radiator hose might not be a great idea in case the thermostat shut, causing a change in temperature of the coolant between the thermostat and my switch that does not accurately reflect the temperature of the whole system.

Sorry for not being clear about where I have mounted the switch. Basically, I cut my upper radiator hose halfway up its length, made a special housing to hold the switch, that the halves of the upper hose clamped onto. So the switch is reading temperature mid way up the upper radiator hose.
 
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RonD

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Upper rad hose is fine for mounting temp switch but it needs to be on the side or bottom of the hose, top of the hose can get air inside so temp sender is not "in coolant" any more.
And of course, a good Ground wire for the Sender.

Heater hose can also be used as long as it is a Bypass hose, has constant flow from engine and back, you would of course want the sender on the "out to heater" hose to get true temp.

Upper or lower rad hoses are thermostat dependent, it decides flow thru radiator hoses.
The heater hose is on the engine side so has true coolant heat inside the upper engine
 

cstarbard

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Upper rad hose is fine for mounting temp switch but it needs to be on the side or bottom of the hose, top of the hose can get air inside so temp sender is not "in coolant" any more.
And of course, a good Ground wire for the Sender.

Heater hose can also be used as long as it is a Bypass hose, has constant flow from engine and back, you would of course want the sender on the "out to heater" hose to get true temp.

Upper or lower rad hoses are thermostat dependent, it decides flow thru radiator hoses.
The heater hose is on the engine side so has true coolant heat inside the upper engine

Thanks Ron! :icon_thumby:

I have the switch sideways and angled down a bit for that reason.

So from what you're saying it sounds like if I had the switch reading in the upper radiator hose or the lower, that in both locations the temp switch should be in coolant that is more or less the same temperature? Is that correct or did I misunderstand that?

Based on what you just said, would it make the most sense to have my temp switch inside the "to-heater" side heater hose?

The more I think about it I guess I'm just afraid that if I have the temp switch reading in a location that could be affected by the thermostat closing, that the switch may be in a pocket of coolant that is sometimes hotter than the rest of the system, which I'm thinking would happen when the thermostat closes. Once it's closed, is it possible that the switch is sitting in a pocket of hot, non-circulating coolant and therefore takes the switch far too long to cool down to the switch-off point? If I should be worried about this, mounting the switch in the "to-heater" heater hose would eliminate that potential problem because the switch would be mounted in coolant that is always flowing unobstructed of opening/closing of the thermostat

Sorry for any stupid questions as always I really appreciate the help
 

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You use a different temp range sender for a lower rad hose.

The control is for the Radiator Air circulation, so using Rad hose for this is fine.

Normally a radiator will lower coolant temp 10-15deg from top to bottom with little air flow
20-25deg with a working fan or while driving above 40mph

Some engines, like 2.3l Duratec, use lower rad hose thermostat, usually 175-180deg model, so upper engine temp would be 190-200degF just before it opened.

So if you used a lower rad hose sender then it would use that temp range, 170-180deg, instead of the 190deg range

But from your first description the fan is coming on, just no going off when it should

The heater hose is the water pump by-pass in most Rangers, so when thermostat is closed flow thru the heater hose is highest, this allows best circulation back to water pump, when thermostat opens circulation goes to radiator but only slightly reduces flow thru heater hose.
The heater hose flow is used for the heater in the cab of course, lol, but also to keep maximum circulation thru the engine regardless of thermostats position.

If thermostat is closed that's a Blockage of the cooling system, there is no way to get coolant back to the water pump since return hose(lower rad hose) has no flow.
That's where heater hose comes in, it passes blocked coolant at the thermostat so it can flow back to the water pump.
The Water pump pumps more coolant than the thermostat's opening can pass, so heater hose always has a good flow of coolant, other wise heater in the cab wouldn't work :)

If coolant in heater hose got too hot that would mean engine was overheating

On most engines you will find the heater hose OUT to heater core on or near the thermostat housing, and with it the ECT sensor and temp Sender for the computer and dash gauge, because this area represents coolant temp after it has circulated thru the heads.

And you can remove the temp sender(for dash gauge) and use its hole for the fan sender, then install the temp sender on the heater hose, not rad hose.
Thats a option

But fan will come on based on coolant temp in engine not in radiator
 
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cstarbard

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Ron you are the best.

I really appreciate all the info.

I'm waiting to hear back from eEuroparts.com to see if they will exchange my switch for me, and I'm going to try another switch and see if the new switch behaves the way I tested, or if my current one is just a bad one.

That should help me understand what's up with this BMW switch, and if its low speed switch off point is just really 106 degrees, I will have to try a different switch entirely.

Yes, my setup works; my problem is just that the fan does not shut off when I would expect it to. Once its on, it just stays on, because the switch's shut off point seems to be 106 degrees, which the fan just can't bring the temp to very easily. I have no negative consequences from that; heat works even though fan is running too much, if anything I'm glad its running too much than not enough. I'm just trying to make sure the setup is working right, so I suppose I ought to try another switch and see if it gets the same results. I'm at the point where its wired properly and works automatically, and I'm hoping to get to the point where the fan only runs for small amounts of time when it's needed and then shuts off. I don't really want to load the electrical system more than I really need to
 

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If its an older relay could the relay itself be the problem.

As the sender is heated the resistance to ground drops, when it is low enough relays coil's magnetic field is strong enough to pull the contact arm down.
If the relay is older it may be "magnetic" so even after senders ground goes back high(cools off) it is holding the arm down.
Try tapping the relay so see if it releases
 

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Mine did the same thing when I had it in the upper radiator hose. The theory I came up with is this.

The engine warms up. Thermostat opens and hot coolant goes through radiator and cools. Engine gets warmer and finally turns on the fan switch. Now radiator with fan cools the coolant low enough that the thermostat closes. Flow stops in the upper hose and hot water stays there. There is nothing to cool that hose quickly even though the radiator is cooling. The hose is a high spot and takes longer to cool. Eventually, it cools or the thermostat opens again admitting more hot water and this cycle continues.

So I moved my switch to the lower hose and the cycle starts the same way. But.... Now, the switch is sensing coolant that has been cooled by the radiator. So it turns on a bit later and shuts off sooner. Hence, I am using the switch with the lower setpoints. I haven't read it with the IR gun yet. But I am happy with my guage reading and the duty cycle that my fan is running. Also, now that the switch is at the bottom, when the thermostat closes and there is no pump flow, I believe there is natural convection flow in the radiator which is still being cooled as the vehicle is moving. Within the radiator and upper and lower hoses, the warmer water will rise and the cooler water will fall toward my switch.

YMMV. But it makes sense to me.

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cstarbard

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Mine did the same thing when I had it in the upper radiator hose. The theory I came up with is this.

The engine warms up. Thermostat opens and hot coolant goes through radiator and cools. Engine gets warmer and finally turns on the fan switch. Now radiator with fan cools the coolant low enough that the thermostat closes. Flow stops in the upper hose and hot water stays there. There is nothing to cool that hose quickly even though the radiator is cooling. The hose is a high spot and takes longer to cool. Eventually, it cools or the thermostat opens again admitting more hot water and this cycle continues.

So I moved my switch to the lower hose and the cycle starts the same way. But.... Now, the switch is sensing coolant that has been cooled by the radiator. So it turns on a bit later and shuts off sooner. Hence, I am using the switch with the lower setpoints. I haven't read it with the IR gun yet. But I am happy with my guage reading and the duty cycle that my fan is running. Also, now that the switch is at the bottom, when the thermostat closes and there is no pump flow, I believe there is natural convection flow in the radiator which is still being cooled as the vehicle is moving. Within the radiator and upper and lower hoses, the warmer water will rise and the cooler water will fall toward my switch.

YMMV. But it makes sense to me.

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Thanks for the detailed explanation. I was starting to think the exact same thing. The only part I'm still confused about is that, if I'm understanding what Ron said earlier correctly, when the thermostat is closed, essentially there isn't flow through the radiator, and therefore no flow through the upper hose or the lower hose. So while I still am thinking in line with what you said above, I'm still confused why the upper rad hose should be a problem or become a heat pocket any more than the lower one would. Unless like you said, it's a high spot and that just causes this. Which I could see. Any further explanation from you guys on that would be great ! I am certainly not a thermodynamics expert lol (I left school before I had to take that course :icon_twisted:)


Ron I think you are onto something with the relay. My gut is still telling me the temp switch is junk, because the kicking on of the fan has become even more erratic, and when I remove the switch from the circuit and just test my relays and wiring, the results are pretty predictable. But, it is a used, likely 20 something year old relay, and the used Volvo relay I had in there before did some very unexpected things.

I have a new OEM BMW temo switch coming (bye $92 :shok:) as well as new OEM Volvo relay... I will switch them one at a time and let you guys know how each and both change how my setup is working
 

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