About a month ago i bought a cooling fan switch and harness from ecklers for part of my spring tuneup on the 86, since that time i have been talking to alvin and will be putting one of his chips in and won't need it. So at this point i will be sending the temp parts back to ecklers and exchanging it for other things i want, the first thing that comes to mind is the drm bias spring. The one they have listed is for 87-96 masters, part #43629 ( mine is a 86 with abs) i have talked to one of their techs and he sez that this is the spring i need because of my abs. So my question is, has anybody used this spring and if so how does it compare to the drm ( is it the same spring under their house name?) And is my master the same as the 87-96 because of the abs? Thanks for any help you can provide. ...joe....

 

I don't understand sending the switch back. Is it a manual switch for the main fan? Even with a reprogrammed chip, it could come in handy at the race track. If it is a lower temp aux fan switch, keep it. Neither the chip from Alvin, nor one from anybody else, is going to affect the on/off points of your aux fan.

RACE ON!!!

 

CFI is correct...I have my fans programmed to come on at 198 and go off at 192...the best they can do in traffic or at the track is keep the temp at 196 running constantly...

I will be getting a manual switch soon so I can turn the fans on at a temp of my choosing....you might want to keep it in case you decide you need it....

 

According to the parts book, 86 and 87 use the same master cylindr. The spring will work.

 

In the last post with alvin he said the temp issues would be addressed in the reprogram (both fans) and that i wouldn't need the sender/harness, it is a unit that comes on at 185-off at 170, +or- 5 degrees, it gets hot here in the summer, i'll double check here to make sure i understood him correctly.Thanks for the help guys,i know this is old hat to you, but it's new to me,...and fun. ...

 

There isn't a programmer in the whole world that can, "reprogram (both fans)" in an '86. Mainly because the axillary fan on an '86 isn't controlled by the ECM.

The "sender/harness" you are planning on returning, must be for the axillary fan. Now that you have listed the on-off temps, returning it is a good idea. Those temps are WAAAY too cool. The car won't run that cold in warm weather and the fan would never shut off. That would be a good way to increase the wear and tear of your engine AND burn up a fan motor.

RACE ON!!!

 

Thanks for your input CFI, since i am just starting to learn about C-4's i can't debate wether or not the fans can or can't be run from the reprograming, nor am i interested in doing so anyway. I simply shared that post from alvin to explain why i am doing what i am, no i don't need to keep the sender, i have been cleaning parts out of my shop for months now and don't want start collecting again, just because it's a different car.
The purpose of posting this was to learn about the possiability of the eckler bias spring being the same as the drm, and to see if indeed a part listed for a 87-96 master cylinder would work on an 86 abs.
Now as for what i ordered being to cold to run, well the best thing i can say is old habits die hard, i have never needed to sleep much so i spend time surfing this and other sites, and while i haven't read every post on this site, i have read most. So yes i have read the pros and cons of running a C-4 hot or cold, and yes i understand why this car was designed the way it was.
Since you live at the top of Utah, you have about the same (within reason ) temps to deal with as i do. We top 100 every summer here and if i cruise down into hells canyon, it hits 110-115+ no problem. Now add to that a gray haired guy that grew up around small blocks when they would start melting at 200+ and you have an idea why i ordered that.
I would like to thank you for your help in what i am trying to do, i like everyone else here, am learning as i go along. However, in the future i will not be explaining my actions. Again thanks for your help. ...joe...

 

I believe I answered that question promptly, accurately and without bias.

 

Believe it or not, your C4 can handle those temps with a stock set up and was tested for such. The aux fan wasn't added for those temps either. In fact, figuring out why it was added (other than to pad the sticker with another $100 for $15 worth of parts), is something I've never figured out. A lot of Vettes left the Factory with only the one fan.

If you want to control both fans with the ECM, splice the ground side of the Aux Relay into the driven (or ground side) of the Main Relay and don't use the switch. Most of the low temp switches offer this harness, but their purpose is to change the control of the Main Fan to the Aux Temp Switch (no programming changes are needed). Having the Aux Temp Switch controlling the fan gives up the engineering built into the ECM, which includes signals from the a/c pressure switch, vehicle speed sensor and engine coolant temp sensor. If you feel that the OEM was Dilbert designed, then use this method. Otherwise, ditch the temp switch altogether and control both with the ECM after you have it programmed to whatever temp you're sure beats the General's design. While you're at it, upgrade your alternator to something that can handle the load of both fans, the a/c compressor and the blower running on high (the stock can barely manage with one fan under these conditions). Otherwise, as you sit at a stop light, it may quickly drop to battery voltage and then something less than that. The fans will slow down, the coolant temps will rise and your engine might start to run a little crappy as the ECM increases injector pulse width with the reduction in system voltage.

If this is you're first computer controlled car, it's nothing special - everything built in the last 20 years or so works pretty much the same way (though some of the trucks still use a clutch fan to control coolant temps). If you want to learn more, pickup Ben Watson's Chevy Fuel Injection at Borders or Barnes & Noble and also order the Shop Manual, though make sure it includes the Electrical Supplement as you are going to be relying more on the schematics once you learn everything that Father Ben has to teach you (plus some of them have a bunch of mistakes anyway).

 

Incorrect. The ECM does receive a request for the aux fan when the A/C is on. The same channel can also be used to provide an on/off temperature controlled program when the a/c is not being used.

 

I'd like to see that wiring schematic. I am 99.44% sure that the ECM has ZERO involvement in the aux fan operation in the 1989 and earlier cars. How about it, Agent 86? Can you provide a link to the wiring diagram to the .pdf file you have of the aux fan circuitry?

RACE ON!!!

 

Quote from section 6E3-C12-2 (Drivability and Emissions section) of manual. " When A/C is used, the fan control switch mounted in the A/C high pressure line will open when head pressure exceeds 233psi and this input causes the ECM to ground circuit 335."
If you check the front end schematic and follow the hot lead from the "Heavy Duty Cooling Fan" back to the relay you will find circuit 335 there. With the heavy duty cooling option, there is no 335 circuit on the Main Cooling Fan relay. The 335 circuit also contains the Water Temp Switch. The ECM will override the temp switch and apply ground to the circuit if necessary. You write a program to ground that circuit based on temperature rather than pressure from the a/c. However if the A/C is operational, it will override the temp program if conditions require it.

 

I'd like to be able to see that. My FSM doesn't have a 6E3 section. It stops at 6E2... My MAIN fan is thermo-switch controlled, not ECM controlled, so my book doesn't relate to what you are saying. It appears I have an opportunity to learn something, here.

RACE ON!!!

 

Either a mistake in your Manual - or you've misunderstood what the circuitry is. Check the Updates or the Electrical Supplement or even the Bulletins - better yet, just check the wiring or review Section 31 in 8A. ECM took over dual fan control in '90 - a real bugaboo for those owners who buy the coolant fan switch and don't know where to install it (the head is plugged). For those of us with the lesser Years, were stuck with a rather old fashion switch for the Aux and ECM control of the Main.

PS: When it comes to a/c - pressure is temp - about 135 degrees at 233 psi - that's why the Condensor is in front and why a/c operation is exempt from Emissions Laws - it's got to be cooler (and more polluting) to be efficient; but what the heck, all the ECM knows is electrons.

 

I'll leave these up a few days for you.

RACE ON!!!!!

 

Key phrase is "causes ECM to ground circuit 335" Circuit 335 is linked to the relay controlling the heavy duty aux fan. I have the ECM controlling the aux fan in my car via a program linked to the 335 circuit.

BTW, Alvin burned the chip.

 

PERFECT!
Your postings prove my point, EXACTLY. Your Chart C12B is for the main fan not the auxiliary fan. Several circuit numbers don't agree with the schematic you supplied. For instance, the 12 volts from the relay to the fan motor is #902 for the main fan and #903 for the aux fan, both BLK/RED, in the schematic. Chart C12B shows that circuit to be #936, a BLK/PNK wire, for the main fan. The ground for the fan motor, in chart C12B is circuit #150. In the schematic, it is # 151. The circuit 335 in the chart is circuit #935 (for the main fan) in the schematic. The text of Chart C12B "says" circuit 335, but it is referring to circuit #935, for the main fan. The text matches the misprinted graphic. If you trace circuit 335 in the schematic, which is the ground for the primary relay circuit for auxiliary fan, you will see that it runs from terminal "B" of the axillary fan relay, directly to the axillary fan switch. Circuit 335 has no splices or interconnections that could ground circuit 335 anywhere other than the aux fan switch.

Thank you for your postings and confirming what I THOUGHT I knew. The downside, is that I failed to learn anything.

RACE ON!!!

 

i dont understand, my 86 only has one fan. Does everyone else have an aux fan on theirs for that year?

 

Are you sure? The auxiliary fan is in FRONT of the radiator. However, it WAS an option, and you MAY not have one. Your gauge temp sending unit is screwed into the right side head, between the spark plugs for the #6 and #8 cylinders. Check the corresponding hole in your left head, between the #1 and #3 plugs. If that hole is plugged, you DON'T have the aux fan switch. A switch, with a single wire, indicates that you have an auxiliary fan.

RACE ON!!!

 

Wrong again. #351 runs to the ECM from the AUX fan relay. The first segment with the narrative only states what is used with the base option. When the heavy duty option is present, the schematic changes with some options (A/C fan control) going to the second relay for the AUX fan. The AUX fan is positioned right on the condenser so it would make sense for it to have the ECM control it via the high pressure switch in the A/C system, not the main fan. Further, with heavy duty cooling option the dotted line schematic you refer to as incorrect is actually correct. Say what you want but the ECM controls the aux fan in my 86 with only a reprogram of the chip and no modifications to the harness. The key again for the last time is that the ECM can if needed ground the 335 circuit for the A/C if needed and that opens the door for the optional fan program based on engine temp to be included. It's just being used as another source to ground the 335 circuit.This is only on the AUX fan when equipped with the heavy duty cooling package. I you still don't get it, call Alvin and let him explain it to you.

Regards
Artie


PS: If this is considered hijacking the thread, my apologies.