Just to re-capp, I bought this car, and '86 FB 2.8L w/ MPFI for $300. My strategy is to make all the minor repairs, paint it, enjoy it for a time, and then sell it to some German for an exhorbitant amount.

I've managed to fix everything but for two things. Engine code 34 and the cooling fan. This essay pertains to the cooling fan but both are related.

When I bought the car, the fan was wired in pure ghetto fashion, straight to the ignition switch -- with speaker wire! I wired it back up, bridged the fan relay terminals and the fan came on.

I have tried warming up the engine to see if perhaps the system still works but of course, this car has only idiot lights so there's no easy way to determine when the fan should be kicking in. I'm afraid to run the engine too long for fear of overheating it.

I measured the voltage at the relay and came back with some funky readings, though. The other thing I noticed was that the wires going into the relay were bare, leaving about 1/4 inch of each wire totally exposed. It almost looked like they had overheated at one time. Confused, I moved on to troubleshoot the code 34.

I had checked the codes using the jumper wire on the diagnostic plug many times before. But this time, when I jumped the terminals............ the fan came on?!?!?!? I find this to be very strange.

Questions.

1. Has anybody ever experienced this phenomena?

2. The fan relay can be closed by way of either the temperature switch or the ECM... Why both? Is this some kind of built-in redundancy in the event that one fails?

3. Where is the temp switch located on my make of car? I think it's on the front left cyllinder head just above the exh manifold.

 

Can't help you too much but I do know that the fan IS supposed to come on when you jump the diagnostic terminals.

 

Really? I never knew that. Of course my last two f-bodies had flutch fans. Maybe nothing is wrong at all then. I wonder if the previous owner freaked out when he saw that the fan was not running upon initial start-up. Unfortunately I never got to meet the guy.

Pat

 

I fixed my fan while using idiot lights.
It's easy.
Open hood, start car, have a brew.
By the time brew is done the fan should kick on.

The fancy wiring job is courtesy of an idiot that worked on the cooling system.
My relay wiring is just like that.
Solution.
Electrical wiring,
electrical goop to seal out corossion, then somehow wrap it
Or use electrical tape, warp around wires, cover with black duct tape.
Second choice is my solution.
AS LONG AS YOU REMOVE THE PROBLEM (bad motor that froze & melted wires was mine) needn't worry.
My system has been correct for over two years & works great now.
Still original rewrapped wires.
Fix to original, observe the fan cycling on & off (WITHOUT AC activated) & you're done.
THEN make sure all fan shrouds in place.
You'll know overheating by steam in front passenger side corner.

I need to install the front plastic directional pieces in the radiator air flow.
Mine will be better, then.
Check condition of the radiator. Is it original aluminum?

 

There is not temp fan switch. There is the temp sensor for the computer which is under the intake by the termostat hosing. The other temp sensor behind the A/C compressor on the head is for the dash light. The computer turns the fan on when it sees 235 and / or the A/C requests it. If it stays off when you start the car and doesn't set any codes then the computer side is FINE. If you jumper the relay to turn the fan on you can check it that way and also check to see that the relay is getting power.

CODE 34 is a bad Mass air flow senosor.

 

Sorry re read your post your fan is working perfect if it came on with the terminals grounded.


Also if you want to run your car cooler, use a hypertech fan switch from summit. There is a water plug next to the computer's temp sensor. Take it out and put in the fan swtich there and wire it so that it grounds the relay. this will turn your fan on at 195.

ALL TEMPS in american.

 

That sensor in head behind AC is also the one used for the water temp gauge, too.
Correct?

 

ON the 1990 - 1991 when they changed dash and went to the 3.1 the temp sensor behind the A/C on the head is for the temp gauge on the dash. I'm not sure about the other years.

 

That answer works perfect for me
Thanks Ryan!

 

As you said, the relay seems fine but that doesn't rule out a bad sensor or high resistance. Now that I know where to look, I will look into this tomorrow. IAW the schematics posted on this site, the ECM lead is labeled fan pressure input. The other lead runs to the so-called temp sensor / switch. The diagram suggests that either lead could ground the relay.

In response to the above reply, I have tried the bottle of beer aproach. I even drove it for a mile and then let it idle and still the fan does not cycle so like, what gives? Will this thing ever kick in?

As hot as these cars run, maybe I could get by with just running my heater on full blast all the time -- just a thought.

Doesn't code 34 mean high MAF vaccum?

 

Well... there's an MAP sensor on 90-92 3.1 cars, driven by vacuum, but the MAF sensor is between your air box and rectangular "air duct" (before the throttle body hose). It measures air flow directly, and doesn't work off of vacuum. Here's a message to help with code 34 and the MAF (34 is "low air flow")... https://www.thirdgen.org/techbb2/sho...hreadid=131873

 

You would definetly know if you are overheating.
After I swapped all my components into place, I tested as I sugested.
My fan cycled on & off.
I am at a loss for your solution UNLESS
YOU HAVE LOW CHARGING ALTERNATOR.
If your alternator is weak, your fan will not kick on, properly.
Found this truth out hard way.
Beyond that, does fan motor work hotwired?

 

I tried your troubleshooting procedures the other day. What happens if you get a reading in between 1 and four volts. Also, why would the MAf have current passing through it with the ignition off? My gut says it's either the ground or the sensor. As for now, I'd just really like to see my fan turn-on by itself.

 

The fan runs just fine when I jump it and the car's running. Tomorrow I will check the temp switch.

 

Keep narrrowing it down.
Good luck!

 

I still haven't determined whether my fan's coming on but I did get it to pass inspection and I got it licensed! This was not an easy task. I drove it for the first time on the highway. It ran pretty smooth but it can't take a hill at over 35. I'm think it must be running in limp home mode because of the code 34.

 

Hm... damn good question! (Why would MAF get voltage if ignition off.) Maybe I typed that bit of the chart wrong? Only other thing I can guess; since the power is off to the car, the MAF relay isn't powered up. With no power to the MAF, it doesn't complete a circuit between the B terminal and itself, and no voltage actually passes through. But when you use a meter, you complete a circuit, and see voltage. But yeah, doesn't make sense. I'll look at the chart tonight.

Between 1 & 4 volts, I'd think either ground, or something wrong with that wire at the ECM. Did you go further in the chart, into 1A? Check voltage at that connection on the ECM. If it's 4 volts (correct voltage), it might be a short in the wire leading into the engine compartment. A GM Technician would fix that wire by leading a brand new wire into the engine compartment. They don't bother pulling the old wire out, they just disconnect it, and run a new one. Problem is, you'd have to get that wire into the engine compartment somehow. So maybe trace the "B" terminal wire from the MAF backwards, and see where you can probe to get 4 volts, then run a new wire from there.

You could try running the rest of the chart starting at "2" and check the rest of the circuts.

 

Dude! Cut yourself some slack, get yourself some of those aftermarket gages and install 'em. Install 'em just temporary if you want, take 'em out later. I just bought an S10 with a worn out 2.8 - rings gone, smoking like its burning old tires. First thing I added was a set of gages - 19.95 at walmart. I found that the engine was running warmer than it should, but it wasn't setting off the idot light. Partially stopped up radiator. Replaced radiator before doing an engine swap... Driving a car where I can't see what the engine is doing gives me the itch.

 

Ditto's about the idiot lights. But I'm a cheap bastard who'd prefer to keep the costs low on this project. All I really have to do is verify that the fan is coming on. All I should have to do is ground out the temp switch and it should turn on. Unfortunately, my job doesn't allow me much quality time with my ride.

 

"Unfortunately, my job doesn't allow me much quality time with my ride."

I can relate, right now I'm workin' two jobs, one to support me, one to support the Firebird. (hey,u do what u gotta do)
I can respect your decision not to use A.M. gages, somepeople don't like to change the stock look, etc. Overheating, in the winter, in Germany, shouldn't be a problem.

 

Although, you could buy a gauge just for testing purposes, under the hood... if you test alot, you could use a T-fitting in the block. Screw the factory idiot light sensor into one port, and put a pipe plug in the other. When you want to test, remove the pipe plug, and hook up your gauge.

 

Well if your going to do all that trouble why not just get an after market temp gauge and mont it on the dash and forget about the dumby lights.

 

Actually, I was thinking about ducktaping a hamster to the fan shrouding in such a position that the blade would decapitate the poor ole' bastard! I DON'T KNOW! But I've done all of the troubleshooting and I think I will be needing a MAF sensor. Where can I get ahold of one of these online? AC Delco doesn't have an online mail order service and besides, I'd rather go aftermarket. Cheaper and all. So how do I get one shipped to me?

 

Go visit your NEAREST OPEL DEALER OR OPEL WRECKING YARD
They are Bosch units.
Specs are 6 cylinder usage.
And end plug adaptability.
YOU should be able to locate that so easy!
PS My 1975 Opel Fuel Injected Sport Wagon used Bosch L-Jetronic, same as Porsche/VW/Audi maybe Lotus. I was able to get parts OK that way for a bit.
Don't they have Hollander manuals in those wrecking yards?
ALSO try
www.pepboys.com
www.kragen.com
www.gmpartsdirect.com

What about your local Yellow Pages/PX/US Military base garage?

 

There's auto parts stores online, a few that come to mind are http://www.carparts.com and http://www.expressautoparts.com and http://www.partsamerica.com ... maybe they ship overseas.

 

All,

I finally found one online. Put it on and it ran fine. However this morning as I was warming the car up, the SES light came back on. It still runs pretty strong (for a 2.8!) so I checked the code and low and behold, code 44, lean exhaust.

My hypothesis: It's been running in protective mode for a long time now so it's probably been running overly rich which may have fouled the sensor. In fact, my plugs were so fouled when I bought the car that it wouldn't start. Also, code 44 wasn't setting before since I believe the ECM ignores O2 inputs when the car is in 'limp home'.

Your thoughts?

Pat