GREGGPENN

In case you don't want to read the rest of this first post, I'm looking for someone who's recently installed (converted) their block fan switch to a lower turn-on. In some early models, I believes it's the main fan switch. In later models, it controls the AUX fan (BP4).

I'm looking to drop my turn-on temp to the lower 200's (i.e., 205ish)

BACKGROUND: In this thread, I once posted the alternate block switches and their turn-on temps. (The one I used at the time of the posting was: 14043275/BW4. Last spring, I had to replace it because the "nose" broke off. I ordered and installed the exact same part (from Advanced Auto) and put it in. That switch doesn't turn on as low anymore. In fact, it works the same as the OEM switch....which was a huge bummer to me.

I was left wondering if the specs had changed OR if I'd gotten a faulty switch? Actually, I think I returned it, got another and had the same result.

I probably ordered the BW4 because I think that's what AA carries. Not sure trying the other brand would fix the problem? That's why I'm asking what people have used RECENTLY...in case manufacture specs have changed. FWIW...the online specs for that BW4 show something like 220 +/1 15-deg. (I didn't look this year, but I did last year. I think the OTC salesperson provided these specs after purchase).

playsdixie

didn't catch the year but on my 85 z51 I simple interrupted the ground wire to the fan to a grounded three way switch (toggle) I installed on my dash....I can turn the fan on or off with the flip of a switch....didn't cost 5 bucks to do....

WVZR-1

Perhaps a Maradyne MFA109 and change to a spade connector. Call them and ask for +/- tolerance and maybe length 'under-head to tip' of the assembly.

Maradyne advertises 195°

http://www.maradynehp.com/mfa109.html

jv9999

On my '87 I installed a 195F switch in the head (have a 160F thermostat). I also swapped the relay wiring around to the switch turns on the main fan and the ECM turns on the aux fan. Also there is a diode that will trigger the main fan relay if the A/C is on. In the summer with the A/C I've never seen it go over 210F.

GREGGPENN

Thanks for the feedback....Still looking for lower 200's though. 195 (as already tried) just doesn't turn off the aux fan...so it ends up running ALL THE TIME after it's triggered.

(I've converted back FROM 160 to 180 stat. OEM was 195. Off all three, I like 180 best)

Switch option isn't preferable unless you are OC about watching temps. Too easy to miss it JUST ONE TIME which is why they make these things auto-mat-ic!

Hot Rod Roy

Gregg, by this time, you're qualified to be the guru of CTS's! Yep, that's what will happen when the turn-off temperature of your CTS is too close to the thermostat temperature. The CTS stays on to keep the fan on, trying to REDUCE the temperature of your coolant, but that will cause the thermostat to close a bit, because it's trying to RAISE the temperature of your coolant! The thermostat will win that battle!

bjankuski

Hypertech fan switch 4028 is 200 on 185 off. Also jet makes one and I think greg from Blowerworks has one. That will only control the aux fan, the main is controlled by the ecm and needs to be programmed. You could jump the relays together and turn both fans on at the same time.

playsdixie

that's why I put the aux fan on manual....can't see that it helps that much anyway....My fan turns on at 175....180 t stat.....never even see 190 unless the air is on....I live in s florida.....

WVZR-1

If you don't deal with the vendor(manufacturer) directly and ask for tolerances before placing an order your 'future' switch experiences will be similar to your previous experiences. You're relying on what/where for the temps that you suspect are happening?

There's many 'resellers' that are actually 'box stuffers' so if you have no discussions with prior to purchase I'd expect results similar to what you're experiencing.

Your desire for a '1st hand/recent' experience is 'simply silly' unless they can confirm with rather elaborate testing equipment what's actually going on.

There's way more to cooling than the damn switches. Just because a cooling fan 'turns on' doesn't mean that it's anywhere near operating at design specifications.

There's cooling system modifications that do work.

GREGGPENN

Agreed, but I subscribe to the THEORY that switches are likely made in batches. As such, switches from "batches" seem more likely [to me] to perform similarly. I don't remember people complaining about the BW4's (at the time of my linked thread in OP), so they "worked" as desired back then. (Or so I thought).

I'm relying on the combination of dash temps and ECM temps (IOW both sensors) to determine where I'd like events vs where they are happening. This discussion is in my linked thread.

The next two paragraphs seem to repeat what's covered above.

It sounds like you don't think I've considered my situation as a "system"? I've studied/changed radiator, waterpump, temp sensors, fans, 383 heat, ignition timing, cam timing, cylinder wall thickness, and Vizzard's recommendations for compression. Give my more credit than your conclusion seems to conceed. We've both been "around" for enough time to know we're beyond beginner status.

Edit: FWIW....Bill Shroeder replied that he used a sensor from AutoZone that operates where I hoped. He didn't confirm with model#/make though. He also linked to kits from CorvetteMods with different turn-on temps. I'm only interested in a CTS though. If all else fails, I will consider Brian's suggestion of triggering the aux fan (relay) with the main fan's relay.

WVZR-1

I suggested a 'conversation' before a purchase from actual vendors. I gave a possible vendor and part#. They also do a 185° so you discuss tolerances of both. In post #7 there were valid suggestions and you maybe discuss with the 'actual vendor' NOT a reseller the manufacturing tolerances. There was a GM 3053190 used in the GN 3.8 Turbo & 3.8 Turbo Trans Am multi-stage configuration. That has been reported by GN folks to be as low as 203°. A Wells replacement mentions 210° on 205° off but strangely they don't mention tolerances. That's unusual for Wells

You want a switch you have a conversation with those who 'switches and fans are their business'.

The swap mentioned by jv9999 would certainly be a valid attempt.

Whose fan, shroud and motors are you using now? How old?

BlowerWorks

I have in stock 3 pieces that turn ON @ 208F and OFF at 201F. $20 ea. I also have the Packard connector and pin.

Hot Rod Roy

As a design engineer, I'd be very suspicious of a CT Switch with specs like that! Plus/minus tolerances unknown? And those on/off specs will change some with age. Expect a short life with specs like that!

Gregg, several of us have expressed our satisfaction with the ACD D1855B, but you keep looking for something better. Good Luck! Have you embarked on a testing program?

https://www.corvetteforum.com/forums...an-switch.html

Does my post #6 make sense to you?

WVZR-1

Suspicious? That's hilarious. As a 'design engineer' I'd have thought you might have picked up on the:

You want a switch? You have a conversation with those who 'switches and fans are their business'.

Hot Rod Roy

Dave, you've said yourself that this kind of information is almost impossible to get from the manufacturers. Since you're so smart, why haven't you provided this information to Gregg? He's been trying to find an answer for his questions for a loooong time! I don't enjoy being laughed at, and am about ready to check out of this forum, because of your harsh comments.

WVZR-1

What was 'harsh' about that comment? The GN switch was used for only a fairly complicated 2 speed fan operation with a very different scheme for the times. '86 - '87 and then '89. It makes sense it had 'tighter' tolerances because of the fan operation.

Who laughed at you? Hilarious was simply a comment to your 'suspicious'. There's very good reason I'd think to be 'suspicious' of any switch offered as an after-market replacement for an OE, any of them!!

Greg mentions a switch he stocks! I'd think a conversation with Greg could be considered 'very reliable'.

GREGGPENN

No one mentioned use (or availability) of the D1855B in this thread. My linked thread (if no one noticed), was compiled in 2012...basically six years ago. What I posted in 2012 was true then...but the specs have apparently changed for one sensor....the one I've used.

If someone has bought/used a D1855B within the last year/so, I'd consider it -- if the turn-on is mid-upper 200s with turn-off in the 190s.

Greg's suggestion sound good though I'll have to figure out the type of end he's talking about.

I understand the issues with picking a CTS correctly integrated to my system. I've set my main fan turn-on to 195 with turn-off at 188. Any CTS below 205ish ... with a turn-off at 180....or even 185 isn't something I'd use...or recommend to anyone with a 180 stat. Just because stat temps close at 180....doesn't mean the block/heads don't have spots higher than that temp.

The BW4 I used last year "published" something like 210 turn-on with +/- 20-deg tolerance. To me, that tolerance is intolerable! And, though it worked in 2012, they've apparently taken the lazy way out now. My GUESS is they stopped making that specific sensor while substituting a higher-value unit for that number. It would be based on an assumption that high temps have become the norm for emissions reasons.