85Irocbuild

Hey all,

I just finished the rebuild of my 305, and its running good. I'm pretty nervous about the engine overheating now, and I noticed a couple of weird things about my cooling fans. I have the stock dual setup. First, when I start the car, the primary fan spins for about 10 seconds, then shuts off. I have not seen it come on at all since then. I replaced the Coolant temp sensor in the rebuild, but the fan just doesnt seem to want to turn on? Also, my secondary fan will not come on when I turn on the AC, but the fan does run when I grounded the switch to the frame. I did replace the fan switch during the rebuild as well. Bad relays? I'm more worried about getting the primary fan running.

DJP87Z28

Since both fans work lets start with what Temp are you running?? Drivers side fan is controlled by the ECM (Temp regulated) . Passenger side comes on with A/C when the Temp reaches 230+/- 10deg. Also make sure you have a air dam under the car.

85Irocbuild

running new thermostat, Ccoolant temperature sensor, and fan switch. All of them are stock replacement.

85Irocbuild

And my temp gage hardly works, I'm trying to fix that too. when I took it for a drive for 20 min or so, the fans never came on, which I thought was odd, so I went straight home and shut off car. No coolant was boiling over or anything, so I don't think it overheated. Do they usually wait to come on that long? Seems like an awfully long time. maybe that's stock though

mantaguy

iTrader: (5)

The fan comes on at 230*235*,usually when your driving they don't come on at all,only in slower traffic.I suggest that you buy a laser temp light and test when the fan kicks on in the driveway and note that on the temp gauge.

deadbird

Any ECM controlled fan, despite year, is turned on at a temp of 220°F. The fan switch (in the passenger head) turns on (grounds) at 238°F.

At any point below those temperatures, during normal operation (no a/c on), the fan(s) do not operate... ever.

Blade09

I actually am in the exact same boat as 85irocbuild. I just got my car running with the new engine combination this week. As I was tuning I noticed it getting hot (220+ on my laptop guages and 240+ on the dash gauge). After reading this I suppose that maybe my dash is just reading a little high and I didn't let it heat up far enough to turn the fans on. Although, I am running a little higher compression for a street motor (~10.5:1) so I would like it to maintain a slightly lower operating temp.

Anyone know of a switch that grounds at a lower temperature? Link or part number would be much appreciated.

Thanks,
-Dan

formula1LE

iTrader: (3)

Try using or cross a referencing Wells #SW505. It is advertised as 212/202 on/off. I think the BW # is TFS4 but don't quote me-Im not at the shop to verify with my cross ref sheets but I believe that's right. The Wells # is correct so any parts store can cross that number over. Keep in mind the location of the coolant temp switch can vary when it grounds as well-cylinder head being the hottest location and water pump inlet coolest.

Ron U.S.M.C.

Or you can use the switch in the head as your primary with a 180* thermostat and the ECM controlled fan coming on at 220* as back up.
Here's the switch = http://www.jegs.com/i/JET+Performanc...60600/10002/-1
That switch is "on" at 195* and off at 185*
With the 180* thermostat that should help keep your car cooler.


Like myself there are those that do not like there cars to run very far over the 200* mark.

85Irocbuild

Hey all, sorry for not keeping updated. I put a new sender into the head, and temp gauge is working now. I decided to test the fans and let it idle. The gauge got past 220 and was about to hit the the red when I shut it off. The fans didn't come on at all. I know the motors work, since I grounded the passenger fan and it spun, and the primary fan spins for about 10 seconds upon startup before shutting off. Is that normal? What can be done about these fans not coming on? I replaced the Coolant temp sensor during the rebuild, so I don't think that's the problem. I also replaced the fan switch in the passenger head as well. A friend told me it could be the relays??

Ron U.S.M.C.

So you grounded the wire going to the switch in the passenger side head and it spun.
If that's the case either the switch is stock and is set to 23O*give or take a few degrees (IMO Insane) or its just not working or the temperature gage itself is off. Not the sender but the actual gage.
Even with a new temperature sender and the coolant gage moving it does not mean its correct. A lot of times the gage itself is off. Just to get it out of the way and eliminate it as a possible problem I suggest taking it to a shop and have them point a laser temperature gun at the thermostat housing and the senders location and compare that to the gage. That service is usually free. Or you can buy a gun for around $25.00, $35.00 at Harbor Freight /online, etc.
Just ground the fan switch where you can get to it easily and use that to get you to a shop and back.

Then you will know how accurate your gage is.
If its correct I would do as I suggested in post #9 and that will give you a fan you can use as your primary. And it will put you on the road. Then you can focus on the ECM fan.

85Irocbuild

Thanks! I'll try and get it to a shop tomorrow to test the gauge. But is it possible for the relays to be bad that are not causing the fans to come on at temp? Sorry if that's a dumb question, I'm not too familiar with wiring. I also ran it again today and the passenger fan didn't even come on when i turned on A/C at operating temp. Also, is it normal for the primary fan to spin for 10 sec or so upon startup?

Ron U.S.M.C.

This is a 1988 TPI
I scanned this to my computer from my $25.00 Chiltons Manual I bought at AutoZone = Hint, Hint
It shows what the circuits look like.
I have not actually played with stock fan relays or there wiring for that matter. I just build circuits around them.

85Irocbuild

Hey all, just updating some finds I had. So I disconnected the relays an jumped terminals A and E on the connector together, and the fans spun. I then put a test light on terminal D with the key on, and the test light lit up, so I'm good there. So what is left that could be the problem? I went on a drive again yesterday and neither one of my fans came on, and the car was about at the red line. The secondary fan does not come on either when I turn on AC to max at operating temp?? I replaced the fan switch during rebuild. Any ideas?? Pleas help guys, I went to get driving my car again.

1992Vortec

What is the 8th digit of you VIN? and all the wiring/ECU is from a 1988? So when looking at the info on all data if you in fact have a cooling temp switch that controls ground to the relay (makes sense seeing how you ground it and the fans come on) then i would say you have a bad switch. Not the first cooling temp switch new in the box to be bad. But you said you replaced the sensor are you talking about the 2 wire for the computer or the one wire for ground on the relay?

85Irocbuild

Vin F car, and I replaced both the fan switch and the Coolant Temp sensor. When I tested the relays, I was getting power to every terminal except for the one with the green wire with white stripe. I believe this is the AC pressure wire. Maybe that wire is bad, or relay is shot?

1992Vortec

if you ground the one wire that goes to the switch and your fans turn on then you relay is working properly. Now as far as the fans not coming on when you turn the ac on is a different story. So if you can get you fans to come on by grounding the one wire switch then everything is working correctly besides switch its self. If you bought a OEM switch then the fans will come on at 238 degree. Id suggest getting a lower switch like 190 and i bet you will be happy. Dont trust any on the gauges on you dash all of then read incorrect some high some low.

85Irocbuild

Actually just got back in from the garage lol. I backprobed the green/white wire in each relay connector while it was plugged in, and each fan spun with its respective relay. so I guess that rules out bad relays. So since my fans don't turn on at all, or with ac, I'm thinking it's definitely an AC related issue. any thoughts?

mantaguy

iTrader: (5)

Is your AC charged with Freon?the AC pressure switch will not operate the fan without Freon.

85Irocbuild

That could be it, since the A/C compressor seems to cycle on/off every 2 seconds or so when A/C is turned on. Mine has been converted to R134 btw, that shouldn't matter at all right? Thanks!

mantaguy

iTrader: (5)

No,doesn't matter,if it's kicking in every 2 seconds you probably need a shot of Freon.

85Irocbuild

Can't I use R134 instead of Freon? Sorry if this is a dumb question...
since I thought Freon would not work in a converted system

mantaguy

iTrader: (5)

R134 is Freon.

85Irocbuild

sorry bout that, though that was the name of the older refrigerant

1992Vortec

Freon is a brand. Refrigent varys on type but regardless if your compressor cycles it's either too high or low. fans should still work when at temp regardless of ac state

formula1LE

iTrader: (3)

Freon is the trademarked name of chlorofluorocarbons owned by DuPont to which EVERY use of it means royalties to DuPont. This is why offshoot makers now call in "refrigerant" instead. Same stuff tho. There are newer types of "refrigerants" but I don't have any experience with any of it besides R12 and R134a.

mantaguy

iTrader: (5)

Sorry, but I don't remember anyone going to the shop and asking to checkout their CFCs.So why don't we just call it what it is "FREON"

1992Vortec

I'm thinking ''refrigerant'' would be a better suggestion to request from your shop lol just saying DuPont doesn't even use the branded name freon for 134A. Sorry just an out dated thing i see parts salesman use that makes me laugh.

But hey like i said before you can fill that thing with all the freon you can find and that's not going to help your fan issue with the switch off...

see what i did there hahahaha

mantaguy

iTrader: (5)

The op said his fan won't even come on with the AC switch,and I suggested that the Freon was not in the system.

1992Vortec

I was saying when the AC switch was off fans should still work. Anyways i see what your diagram say about pressures on opening and closing switch pressure. This is what all data says the pressures are. making is appear that the high pressure switch is used to shut down the compressor in a over pressure situation. Not to turn on and off fans, usually the low pressure switch is the indicator of ac operation and low charge condition. Not saying your info is wrong just showing the info im looking at so we can get this guy the info he needs. Could you post the fan diagrams for the fan switch in you book?

85Irocbuild

Thanks guys! These diagrams will be very helpful when I do some troubleshooting tomorrow.

85Irocbuild

Well, good news. I got an infared temp gun and let the car heat up, and pointed the gun at the thermostat housing. When my gauge showed 220 degrees, the actual temp was near 150! I kept an eye on the temp gun and let it heat up for another 10 minutes, and it hit near 200 degrees. Then the primary fan turned on! The gauge showed the needle buried deep in the red. The primary fan kept going for a couple minutes, then stopped when it had cooled car to near 180. So I guess my fans do work, it's just that the gauge was WAY off and I never let it get hot enough because I thought my car was gonna overheat! I'm so relieved lol.

NowI have to find a way to may the stock gauge somewhat accurate, since I want to keep the car stock. I had replaced the temp sender with a part from NAPA, and I guess it's the wrong one.

Anyone have a correct OEM part number for the temp sender? I've heard that AC Delco has the most accurate ones.

Ozz1967

iTrader: (4)

Just hit up autozone for the temp sender. My guess though is that your gauge is way off. To recalibrate your gauge, check out Autoinstruments out of california. they say they can do gauges.

mantaguy

iTrader: (5)

I'm glad you got that solvedThat Infrared Temp Gun is one of the "Gotta Have" Tools in the box.I carry mine for just piece of mind

85Irocbuild

Thanks! And the new "correct" temp sender from AutoZone is the one that is way off, but I remember seeing on a thread somewhere on the forums that ac Delco had an oem type sender that was correct for our gauges?

Ron U.S.M.C.

Changing the sender and chasing the problem with a multi-tester is good but the gage should be tested with a gun as you have done. I suggest to anyone even if you don't have a problem test it anyway. Its always nice to know exactly where your gage is at.
Its easer to try another sender but be prepared to fix the gage its self.