2nd Radiator fan...Wire Manual or wire in series??

79X19

79X19

True Classic
I am about to install a new Texas Heat radiator and have installed two new 8" fans. My question is should I wire the fans in series or run wires to set up one fan on a manual switch? I would like to use a stock "On / Off" type switch such as the rear defroster switch for the manual fan switch (if I go that way.) That way it will fit into my console and look stock and not out of place. Also have a few more Q's relating to the installation of the bleed valve and the temp switch. So to summarize:

1. Wire the fans in series using the current wiring so that the fans both turn on once the temp hits a certain limit.
Or
2. Wire one fan as normal with current stock wiring and wire the second fan using new wiring connected to a simple on off type switch? Could I use a stock X switch used for the rear defrost and re purpose for a fan switch?
3. Do I need to used Teflon tape when installing the new temp sensor switch? Pic 5564
4. The new bleed valve came with a rubber type gasket shown in the picture. I assume this goes in as pictured and I tighten the bleed valve snugly? Pic 5563
 

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I'd set it up with a two position switch, as in it turns on at two temp levels; the lower temp goes to one fan and the higher temp adds the second fan. VW temp switches that do this will fit the Fiat rad.
 
I used tephlon. dont know if I needed to, but I did. and I replaced the rubber gaskets with copper. as the rubber seemed to bulge out when I tightened it. Again, not sure if that is what I was supposed to do, but I did on my texas heat

Odie
 
Dr.Jeff said:
I'd set it up with a two position switch, as in it turns on at two temp levels; the lower temp goes to one fan and the higher temp adds the second fan. VW temp switches that do this will fit the Fiat rad.
Click to expand...

would you happen to have year/model or part numbers for this switch?

Odie
 
autox19 said:
would you happen to have year/model or part numbers for this switch?
Click to expand...
Odie, its been awhile but if I recall it is the Mk1 Golf (Rabbit)/Jetta or the Mk2 Golf/Jetta. Those two might even be the same size, Id have to double check. But notice they offer single, dual, and even three level switches (3rd is for AC cut-in). So look for a dual temp switch. Also they are available in different temp settings, depending where you want the fans to come-on/shut-off. The aftermarket offers several choices at all price levels so shop around. Let me know if you don't find what you are looking for and I'll see if I have more info on it.

Any two speed (dual temp) switch can be wired any way you want with relays; one fan at first temp and the other at second temp, or two-speed fans on low-level at first temp then high-level at the other, or combinations of these.
 
If it is an AC car, then there are even further options to have the second fan come on when the AC compressor kicks in.
 
I too have an aftermarket aluminum rad with modern fans. The pass side fan is wired into the factory wiring. For the second, driver side fan I used a Hayden 3674 Adjustable Thermostatic Fan Control to control it. The power for the fan relay comes from my buss bar. The controller has a wire to which you would connect to the wire that engages the clutch for the A/C compressor (if fitted with A/C) so that the second fan will run whenever the A/C compressor clutch is engaged. I repurposed this wire to do exactly what you describe, it's connected to an OEM push button switch on the center console switch panel and functions as a manual override.

IMG_3967.JPG
 
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Hi Generation X,

I have modified my engine and am uncertain how my cooling system will perform when I get to driving. I came up with the wiring diagram below using the 74-78 OEM wiring diagram. Basically it uses the fuse block from the BWM and HLRM, a new relay, and a 3 way switch to power the fan in parallel either through the thermostat or directly, your choice.

PS. new computer and haven't purchased Office 2016 yet so I am only left with snip to retrieve the file, no editing currently.
 

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Thanks for all the replies and information! I went and purchased the washers from MWB to replace the rubber that came with the Texas Heat. The Fan switch comes with a crush washer so that's all set, Hooked up the passenger side fan to the standard wiring and now running wires through the frunk for the 2nd fan. Will wire it separately with separate relay and separate switch in the dash.

Further question is can I use or re purpose a rear defog switch as an on off switch for this 2nd fan set up?
 
I two purchased the Texas heat rad with 10" fans. Old and heavy vs new and light.

Rad New Old.jpg

So being highly electrically challenged (just the thought of the brown wire mod for H4 headlights puts me into a cold sweat) I was just going to wire both fans together by using the connector off the old fan then plug that right into the harness. From what I've been reading here this is called "series" and the fans will run at half speed? Is this because there is a fuse only letting so much power thru and so the two fans have to split the power?

Is there an easier way to wire them up than mentioned above? Like adding a wire with a fuse or something straight to the battery for more juice? I have no problem with both fans coming on together when getting hot then turning off when not.

For those following the Coolant Pipe thread It's on hold since the tenants that rent the house where my X and garage is haven't paid the PG&E bill in many months so the power got cut off and I can't open the garage door!!! Now I have to evict them, happy joy joy!

Thanks, Carl
 
you can hook them up in Parallel. This will give both about 12 (ish) volts. It will double the current. (newer fans might not draw as much anyway). Relay's off the battery and switched from the factory would be the best (install an override to turn them on would be a good idea!)
 
I'd keep it simple. You can build a harness off the original single harness that splits the + and - connections into two connections (one for each fan). I'm not familiar with the Vick fans but most of the newer ones consume less current than the original OEM beast (and also less airflow I think) so unlikely to overload your system.
 
Does anyone see an issue with the photo I posted and it's wiring? I plan to use that when the time comes. Everything in the dashed box, the second radiator fan, and blue black dashed line are newly added by me. The new components are copied, pasted, and cropped to look like they were supposed to be on the page. Basically it uses the same signal used to trigger/ground the original cooling fan relay to ground the switch. When that "dash" switch is to the left when the thermostat grounds both relays trigger and both fans. When the switch is to the right, the signal is automatically grounded triggering the new relay and starting the fan. I need to change the blue/black dashed line to be blue or something.

I thought the 2 way switch would help with bad traffic areas, any cooling uncertainties and doubts, and those rare times with the t-stat fails.
 
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looks like it would work properly and the best of both worlds. You could leave it on "automatic" so the 2nd fan comes-on when the 1st fan does. Or if you want additional control, you can power it on yourself. IF the coolant system is working properly, I don't see the need to manually switch-on either of the fans. They should turn-on only when needed. Mine seems to work well -- at one-time it didn't but that was because I had air in the system which caused the thermostat to turn-on later than it should have.
 
AKimball92 said:
Hi Generation X,

I have modified my engine and am uncertain how my cooling system will perform when I get to driving. I came up with the wiring diagram below using the 74-78 OEM wiring diagram. Basically it uses the fuse block from the BWM and HLRM, a new relay, and a 3 way switch to power the fan in parallel either through the thermostat or directly, your choice.

PS. new computer and haven't purchased Office 2016 yet so I am only left with snip to retrieve the file, no editing currently.
Click to expand...

The only question I have is do you want to just control the one fan with the switch or both. As the grounding wire connection from relay to relay is broken by the switch, if the you kept that joined, grounding the switch would run both fans. So left position of the switch would allow both fans to run when the thermoswitch clicks over and also allow you to then put the switch into the second position and ground both relays to control both fans at the same time.

Just a thought. Nicely done.
 
O.K., I've resisted commenting on this for years because I understand it is just my personal view and I realize others have a different opinion. But I really never understood the popularity among Xweb members to have a manual control switch for the radiator fans.
Not to rant, but in my 45+ years of building cars (mostly modified and customs), I have never heard of anyone (outside of this forum) needing a switch on the dash-board to turn on the cooling fans. Why? Is your cooling system in that poor of condition that it cannot function the way it is designed to? Or can you not repair/improve it to a sufficient state to work without your active control?
Sorry if I sound offensive, honestly I do not intend to. I just can't imagine a reason to feel compelled to have that switch. Does it make you feel more in control (joke intended...do not get reactive, I'm only kidding with that last comment).
But I do not understand why. Please educate me on what I've been missing for the past 45 years on this topic.
Switch or not, I love you all just the same. :)
 
There are a few reasons.

One, the thermoswitches are not the most reliable. Mine apparently failed sometime in the past unbeknownced to me, I only found out at the autox I went to last when the coolant started overflowing. I bypassed it to have it run constantly. In normal driving I never had a problem as my area is warm but not brutally hot and I tend to drive at 40mph and above so airflow apparently has been sufficient.

Two, depending on where you live, many have seen their temps rise when coming off a freeway drive.

Three, having a head gasket blow tends to make one paranoid about any overheating.

If you have owned a 124 Spider, it isn’t unusual to see significant temperature variations in different driving conditions such as California. California is not northern Italy where the temps are more temperate. So people tend to assume the same behavior on other Fiats.

Lastly, yes some of us do indeed have marginal cooling systems and are trying to compensate for that.

Personally I have never added a switch to my cars but have added many to Fiat 124’s for others.
 
Thank you Special K, I get what you are saying. A couple thoughts came to mind as I read your response.

I use German (VW) temp switches in my radiators (including the X, direct fit). They are very reliable (I've never heard of one failing), and they are available in various temperature ranges. So I use one that activates the cooling fans at a little cooler temp than the stock Fiat switch (which is too high in my opinion, but I live where it is hot).

I make sure the cooling system (in its entirety) is operating correctly. This is something I learned long before moving to the intense heat I am currently residing in. I had one experience (many, many years ago) of overheating while towing a boat, which ruined a long anticipated vacation. And it turned out to be due to a radiator in poor condition (my own fault). As Great White said, once bitten twice shy. And now that I live in HELL, I am even more conscientious about it.

I also make sure the cooling system has adequate capacity for my conditions (see the comment above, I reside in Hell, otherwise known as Las Vegas). If necessary I install a larger radiator, improved cooling fan(s), lower temp switch (as noted), lower temp thermostat (if necessary), etc.. Allowing the engine overheat (and blowing head gaskets) is not an option.

Lastly, I do not believe in "bandaids". In my opinion (and it is just that), the addition of a manual control switch is an attempt to solve a problem without addressing the cause. This is a pet peeve in my other profession, where symptoms are treated instead of curing the disease.

O.K., speech over. I'm certainly not without my own shortcuts so I really cannot find fault with those of others. Guess I just felt compelled to express an opinion on this topic.
 
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