Ok I can't take these fans anymore i just want a switch to turn them on whenever I feel like it. They never run when the car is on but both fans work since when i jump it for codes the Driver side comes on and sometimes when the AC is on the Pass does. Both relays are brand new also.

The car: 1988 Trans Am GTA with 5.7 TPI and the dual fan setup.

Wires going into the relay are: Orange, Black/Red, Dark green/white, Tan

All I'm wondering is if i'm correct when I think i'm going to take the dark green/white wire to the fan relay and the same wire from the other relay and wire them to a switch. Would I be correct in assuming this would ground the relay turning it on and starting the fans? And if I am correct then should I wire each dark green/white to a seperate switch or can I wire one to the other than a wire to a single switch? I think 2 switches would be better anyway but just in case. Thanks alot you guys are great.

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1988 GTA 5.7
MSD 6AL, Accell 8.8's, 160 Thermo, SLP headers, Airfoil, Gutted MAF

 

I have a 89 iroc with dual fans. Major headaches with the fan relays. Bad design on vendor end. NAPA AR-279 is a redesigned part that is beefier. I think a hardwire is a bad idea for several reasons. You stop and chat with a friend and the car is running, it will heat up fast. Suggest Jet fan switch for the aux fan. This will turn on at about 180 degrees and run the aux fan until engine cools. Your ECM controls primary fan relay, and a fan switch in the block controls aux fan relay. You can tie them together with a switch but I really dont advise it. I have been very happy with the temp of the engine sine I installed the JET fan switch, engine never gets above 200 even on a hot day with the air on. Good Luck, Dan

 

I just wired in 1 relay and a circuit breaker. I wired them so when the key is on, both fans come on. The breaker is rated at 90 amps. I used a new Boush relay and wired accordingly. It has worked so far.



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Joshua Johnston
1991 Z-28
Flowmaster
K&N
305 / 5spd. (Temporary)
Soon to have:
350, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust, T&R Motorsports custom air intake

 

Thank you for your replies. I have put in gm replacement relay's and NAPA relays and still the fans don't come on. I just went outside and jumped the orange and Black/Red wires together with a paperclip and each of the fans do it on each relay, they start up perfect. And also I have in the Hypertech fan switch in the head and that does no good either. So I am still in the dark about how to go about just making them work.

 

If you have a dual fan setup I'm pretty sure your ecm controls the fan on/off temp. The fan switch is for us TBI guys and carb guys that have single fans. At least that's what I was told (don't have a dual fan OR TPI...).
If I'm right then you probably cut the wires and did something wrong. You said when you turn the AC on the fans turn on so it doesn't sound like the ecm but maybe a CTS sensor or a bad/cut wire from the ecm to the relays. Remember, I'm not positive on the ecm controlling fan on/off temp but I was under that impression.

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, Jon (350 TBI!)
91 Red My website

 

From what I know (which applies to my 87 formy), the dual fan TPI setup (for 87 at least), is just set up that way. For most that don't pay alot of attn to their gauges, it's fine.

On the (87) dual fan setup the main fan (drivers side) is controlled by the ECM, which, uses the water temp sensor (for itself & fan control) in the front of the intake manifold. When the A/C is turned on, the [b]same fan[/] will run. This happens from the A/C pressure switch ungrounding, or 'A/C request' to the ECM. The ECM (or PROM,, I assume the 2nd) is programmed to kick on when it 'sees' 235° at the sensor in the intake and turn back off at somewhere around 205°.
(This is the cause for the car to seemingly get so hot just sitting in one spot)
Electric fans do not constantly run like a belt driven fan so will not maintain a stable temprature such as a car w/a belt driven fan.

The 2nd fan (again, on an 87 TPI), is an emergency fan and nothing more, it it controlled only by the temp switch in the passenger side head. The switch is designed to kick the 2nd fan on in the range of 265°, when it turn off I wasn't able to find out, (I assume it would be close to 235°). This sensor (like the ECM) merely grounds the relay.
The JET switch is the same except modified to ground at a lower temp. making it the primary fan and the ECM controlled as a sort of 'emergency' fan.

The flaw I found mainly in the setup on my 87 is that if the primary fan is running, and for some reason the 2nd one comes on, (which would be an emergency to start w/at that temp) the 2 fans share the same power source(the tiny little 20amp fuse right off the + terminal of the battery modest sized orange wire) and will pop the fuse instantly knocking out both fans.

As I found out through a small amount of info searching, the overheating 'problem' is really what was designed into the car to begin with. Keep in mind, the original thermostat with our cars were 195°, take into account that $1.5o thermostats aren't really that dead accurate. From the showroom floor, our cars were running about 200-210° which, apparently (for stock) didn't hurt a thing & the extra temp also helped reduce emissions.

Sorry that was so damm long, hopefully I kept my ramblings sort of clear and this helps clear up some of why our cars seem to run hot all the time.

Also,, keep in mind, this is information I've gathered about my 87 firebird so I could make some sense on how to rewire the fans, if I'm to understand, there are some variances year to year and what I've said may not apply to everyones car w/a dual fan setup.

<shutting up now

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• my Formula Homepage
• Collision P/Ns & Diagrams (Camaros & some of the Firebirds, more on the way)

The mind is like a parachute, it only works when its open

 

Must be frustrating to say the least. A VERY good explaination by the one guy about how the fans are controlled. The next step is a troubleshooting strategy, and for that you will need to know how a relat operates. The two heavy guage wires you jumped go to feed 12 volts to the fans. The lighter guage wires are relay control. This is the coil part of the relay. One end of the coil will go directly to 12volts with the key ON. This is the source side of the coil. The other end will go to the ECM, or in the case of the secondary fan to the secondary relay which is controlled by a switch in the water jacket of the block. The 12 volts feeds thru the coil and when the ECM calls for a fan turn on a transistor switch in the ECM grounds and the relay will energize closing the contacts and providing the 12 volts to run the fan. In the secondary fan the switch in the block shorts to ground and provides the ground for the secondary relay coil to energize turning on fan #2. You will need a digital or analog voltmeter and an accurate wiring diagram for your vehicle. You can drop the ECM down and go directly to the connector and ground the wire that goes to fan relay #1. If all wiring and the relay are ok, fan #1 will turn on. USE CAUTION, make sure you are at the right pin at the ECM or damage will occurr. Same holds true for the secondary fan. Find the switch on the block and pull off the wire. Ground the wire and relay #2 will energize and turn on fan #2. You could have bad relay plugs. Assuming there are no wiring changes this test will verify what exactly is going on. As a point of interest, my Camaro fans draw about 8-10 amps on start and settle down to about 6 amps when at full speed. You should not have a problem with the fusible link if the fan motors are in good shape. If they are binding, or the bearings are dry they will start to draw more current. Hope this is some help.

 

FYI, on my 1991 Camaro, I obtained the following current measurements on both my factory GM fans, made at 14.2VDC.

Both fans drew essentially the same amount of current.

Start-up current lasted < ~0.5 seconds.

Start-up current: 49 amperes (each)

Run current: 16 amperes (each)

 

Reply to Stu Moss's current measurement. How did you measure current. Peak current I do not believe goes to 50 amps, however the only way one could measure it would be with an occiloscope with a sample and hold feature. True current draw is 6 amps at run speed. Fifty amps of start current is feasible only if one can measure instantaneous current draw for a several hundred millesecont time period. I would respectfully submit that you recalculate your measurements. I stand firm in my calculations as far as electrical load requirements for third gen cars.

 

danno,
That sux. I thought they drew 49 ea. also. That is why a got a 90 amp breaker. I know this adds to 98amps, so if true, it should trip on startup. It doesn't. Well, nothing better than overkill!!



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Joshua Johnston
1991 Z-28


350, T-5, K&N, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust,Dynomax Bullet Mufflers, T&R Motorsports custom air intake

 

Well everyone sorry for the delay here but short after my last post I was driving around and the car kind of sputtered out and died. Since then I found out the problem there was my ECM and I got a replacement ECM put in and now BOTH of my fans run great along with the rest of the car! So needless to say I'm happy everything is working great.
Thank you everyone for your replies.

 

Actually, that is not true. Granted, the start-up current is short, but not that short. If it is was in the millisecond range, then yes, an oscilliscope or peak and hold meter (if it can capture the value quick enough) meter would be the way to go. Actually, one of those instruments would be the preferred way, but I did not have one at my disposal to perform the test.

Nevertheless, the start-up current is slow enough (relatively speaking of course) to get a rough estimate (± ~6 amperes). In doing the test (last year), I used a simple 30 ampere current shunt with a fairly quick reading DMM to obtain the 49 ampere start-up current (measured with a system voltage of 14.2VDC).

Well, perhaps for you, but "true" current draw for my fans is ~16 (can't remember exactly - maybe 17...) amperes at 14.2VDC, measured at the relay socket.

I would agree to this. Afterall, start-up current does indeed take only a few hundred milliseconds (100mS = 0.1 seconds, so a few hundred milliseconds is just as I had originally stated - < ~0.5 seconds - or 500mS) )

I made five measurements per fan (total of 10), with each fan within ~3% of the other. Repeating the test will achieve the same results.

I guess I would have to respond with "I stand firm with my calculations for the current draw of the two stock GM fans on my third generation Camaro". I never intended my results to be taken as the "norm" for all third generation Camaros - only the results of my tests, which differ from your results.

Readers can choose to believe either, both or none of us as to the accuracy of the results, based upon how the information is presented.

 

From my real world tests,, I'd have to agree w/mr moss,,, I can honestly say if both fans activating at the same time were under 20 amps total,, my fuse would not have repeatadly blown, they were factory wired.

My rewiring was the result of an aasumption of a factory fan draw miscalculation. I certainly can say I might be wrong,,, but results speak for themselves.

[This message has been edited by deadbird (edited August 23, 2001).]