FrostyMountain

My 1985 L98 has a concoction of spliced and disconnected wires and i am slowly trying to get things right. Unfortunately I do not ever understand electrical wiring. I have a GM manual on CD, but cant make sense of it. Will order a FSM so i can look at hard copy. Anyhow, my engine has two large fans. One mounted in front of the condenser, facing in, one mounted engine side of the radiator facing out. Originally the one mounted in front of the condenser would come on immediately if the ignition key was turned on , and stayed on all the time. After dismantelling my Radiator for cleaning and reassembly that no longer happens, dont know why. I dont know if the radiator side fan works as it should, as it never ran hot, but as stated the one fan ran constantly. I checked both fan motors by jumping them directly to 12V and ground, both function. One sensor located on driver side between cylinder 1 and 2 has a blue wire going to it, which seems to wire directly to a bracket of sorts below it behind the exhaust manifold, cant see it beyond that. A similar sensor located in the block between 7 and 8 cylinder has nothing connected to it, but there is a green thin guage wire near it connected to nothing. Located the fan relay near the battery. It has a red wire directly connected to 12V, a heavy guage black wire, thinner guage green with white wire , and a blue wire. The green connector that connects these to the reley is severly damaged, needs replacing.

QuestionS : The two sensors i referenced should do something, should I connect that loose green wire to the one by 7 and 8 cylinder.
Can i get a replacement connector to replace that green one that is damaged that goes to the fan relay so i can splice it in for a good connection, if so where and what do i call it.
How do i bench test the relay to see if it is good.
I will replace those sensors in the block as they are cheap, what do i ask for when ordering them, coolant temp sensor?.

Hope I have explained this well enough. Apologies for the length.

FrostyMountain

Addition to the Above. I did just ground the green and white wire to the relay with the key on and the fan did kick in. The instrument panel gauge appears to function as when i started
it up it did show a steady rise in temp, shut it down at 210 and the fan hadnt kicked in yet. Still dont understand why the fan in front of the condenser doesnt come on now as it was always on until i jostled things around. Just dont want an overheat problem to occur.

kenmohr

the main fan turns on at 228* and the pusher fan turns on at I believe 238*. Never had the pusher turn on.

WVZR-1

The BLUE to the LH cylinder head switch/sender is for the gauge on an '85 so you can disregard that because you mention the gauge functions.

The switch in the RH cylinder head is intended to control the AUX FAN in front of and because your GREEN wire is "hanging" it seems that the PO has reconfigured the AUX FAN in some way because you mention it running previously at KEY ON.

The grounding of the GRN/WHT accomplished what's expected I believe.

Maybe you look for a toggle switch somewhere inside the car. Is the PO someone near you? Maybe he knows. I'd ask.

Unless tweaked in some fashion the fan behind the radiator is ECM controlled.

The '85 FSM is in a format of it's own when it comes to wiring diagrams. '86 and later the "diagnostic cells" remained the same or very similar. The PDF CD if saved to your PC will be much easier to use I'd think, most are very "searchable" but it requires terminology that's in the FSM. Once you become familiar with the PDF I don't believe you'll have issues.

I'd buy no switches/senders right now. The LH seems to be doing what's expected and the RH AUX fan I'd think requires correct diagnostics before a buy. NEW doesn't necessarily interpret to BETTER or "working correctly" - NEW parts often create issues!!!

FrostyMountain

Yeah that whole auxilary fan on thing is very weord, cause now after removing and then replacing the radiator, putting in new thermostat etc, it doesnt come on. Previous owner is DOA, bought it after it was stored as the result of a probate court. I looked and cant seem to find a wiring diagram appropriate for this car as it has the Auxilary fan option, and I cant seem to find a relay for the frfont fan, Ill keep. looking. Also i put a paper clip between the A and B terminal with key on, as I understand it fans should kick on, they dont. I will try and find the relay for the front fan, i believe it should also have a green and white wire the same as the front relay fan. If i ground that then Ill keep trying. Thank you for taking the time to respond

WVZR-1

This is what I believe to be correct wiring for '85 DUAL FANS



This is I believe correct relay locations for an '85



This is the related fusible links if OE arrangement. If battery cables have been replaced they're very often altered. They can be a challenge for sure.

VikingTrad3r

good for you for sorting it out and cleaning the rad. if people serviced the rad, which is soooo easy, they wouldnt have to cut up their wiring and moderate so both fans came at once.

FrostyMountain

OK just as a follow -up. I cleaned and did a partial repair of the connector that goes to the fan relay that is by the brake master cylinder. After re connecting it I jumped the A & B terminals of the computer trouble reader (ACDL?) and the fan engine side of the radiator came on, Auxilary fan in front did not. As stated before if i ground the green white wire at that relay, that fan also operates. So it appears that I need to fix that connector permantley and that fan problem may be solved. Also i located the wire that was on passenger side ( green) grounded it, and the auxilary fan came on. I assume if I connect that wire to the switch between 7 & 8 terminal that should make that fan operate properly. Hoping one of you who knows what is going on can read this and see if I'm doing properly.

Couple of questions


does anyone know where I can get the connecter that goes into the Fan relay, its really crushed.

Should i replace the two sensors (or switches) that screw into the block (between 1&2....and 7&8 cylinder, if so what do i call them, or any part numbers .

Does it make a difference that i Have 1 180 degree themostat ( just put it in, it had a 180 in it so i replaced it with same)

Thanks to all for your patience , hope you can help with the above questions

WVZR-1

I mentioned a couple posts ago that I thought it foolish to buy either unless you can confirm the fact they ain't working. NEW ain't necessarily BETTER.

The relay connector if the plastic shell is demolished these days would be a very tough find. The only source that I knew of shows out of stock for the empty shell.

Here's an Amazon offering that looks to be correct or use "Four Seasons 37208" for a search on eBay:

https://www.amazon.com/Four-Seasons-...ype=automotive

See if a local auto parts jobber can get you the Four Seasons 37208 - NAPA maybe?

FrostyMountain

Thanks, I have a tendency to just replace stuff thats not always needed, Ill try to control that urge. I searched at ecklers and it looks like they have the shell that can rebuild the bad one. Their write up also says that the 85 switch should have a Button terminal not a spade terminal like mine have, indicating that many people replace the switch with the wrong switch. Mine definately have spade not round button type on both . Just ran the engine and the auxilary fan kicked on at 220 degrees ( guage temperature), the main fan did not kick in yet Ill take it out tomorrow and see how it goes. Any thoughts on the comments by ecklers that the switch might be the wrong one?

xrav22

I have the same deal going I replaced the sux fan sensor(238on) with a 210 on temp.
So my aux fan comes on at 210 now and that helps so you don't have to turn it iff at 228d.
The big fan never really goes on unless its hottt out. I also went with a 180 degree thermos and it has been fine. Even passed CA smog with this setup. I just sourced a temp sensor from a Camaro or something. My wiring was good but the sensor looks like this


I cant find the source for the connector but its somewhere
Good luck

WVZR-1

That actually looks like an older fan switch. This thread has what I believe is likely the switch OE part# for an '80 - '82 Corvette and an '84. If by chance it's stamped 108C then you could assume 226°. Camaro early and mid 80's for fan and nearly all GM with 12V cooling fan control.

https://www.corvetteforum.com/forums...post1590356371

FrostyMountain

OK , thanks to all, but just for dummies like me who dont understand anything electrical, what are the proper switches for my application , keeping in mind that i have a 180 degree thermostat. As i understand the switch between 1 & 2 cylinder sends info to the guage, the 2 connector switch in the front of the engine by the thermostat sends info to the ECM, and the switch between 7&8 activates the auxilary fan.Sorry if this seems to confuse me a bit.

WVZR-1

'85 FAN SWITCH GM# 14043276 or equivalent

'85 TEMP GAUGE GM# 25036135 or equivalent

'85 ECT/CTS for ECM GM# 25036979 or equivalent

xrav22

That is correct

FrostyMountain

Awsome, thanks to all who simplify stuff for me. On to the next project

GREGGPENN

Has anyone actually bought and installed an aux fan switch that turns on in the 205-210 deg range recently? The historical part (that I've posted before) has a WIDE, WIDE range. I've bought 2 recently and both turned on closer to 230. I returned them.

I also tried the MAM unit but it turns on too low...meaning it'll never turn off...even with a 180-deg stat. More or less, it's turn-on point is so low that you can't "squeeze" the main fan operation range between it and a cycle off condition.

Hot Rod Roy

There seems to be some question whether this "mushroom top" CT switch is right for the '85, but if this is what you're looking for, the ACDelco D1855B is rated at 215* on, 200* off.

(I have this switch in my '84)

WVZR-1

The "mushroom/recessed tip" I'd think stock for an '85(AUX FAN CONTROL) and the D1855B(GM# 14043275) is actually just a I believe "normally open" that closes at approx 215°. The after-market equivalents are all mentioned to close @ 213° - 229°. The wide manufacturing tolerances is why many don't have a pleasant experience with what's purchased recently. OE I believe this switch was only used in the very early A & X-body GM with 2 speed fans. This was the LOW FAN, the GM# 14043276 was used for the HIGH FAN That's how I recall the source originally.

This is how I recall from very early electric fan experiences (Fiero etc)

GM# 3040674-220°, 14043275-215° & 14043276-230°. The switches were generally stamped with a Celsius temp so if you're buying any of the equivalents you might check for the stamped # and of course check and confirm.

FrostyMountain

I had hoped this wasnt as confusing an issue as it is. The 85 seems to be a bit of an anomoly. Corvette Central sells a cooling mod kit that they say goes on at 200degrees and off at 185. Has anyone had experience with this. I checked their online tech guide for this, but its wiring instructions seem to say that the switch between cylinder 1 & 2 operate the fan, which for the 85 is not true. Anyway has anyone any experience or opinion with their mod kit. Thanks to all who respond, i learn a little every day. I warn you, my next projevt is R&R of the fuel delivery system from the pump forward to injectors, wish me luck