Auxillary Fan
 

I have a question regarding the stock auxillary fan on my 1986 k30.
The fan is still working as I have supplied power to it and it kicks on... the problem is that when plugged into the thermostat/reostat (not sure which one it is) on the passenger side of the 7.4L, there seems to be constant power to the fan. This is a problem because the fan circuit has constant power (even when the truck is off).

SO, my question is, what type of thermostat/reostat should be on the 7.4L and what do I need to replace to get this back in working order?
Currently, there is just a female blade style plug that is connected to what I'm assuming is the wrong thermostat... but I've definitely been know to be wrong. I'll try to get some pictures up asap but would appreciate any input from those of you who are familiar with what I'm talking about.

When I talk to the local parts store, they show a thermostat that has a different style plug that I do not have, which very well could be the case as the PO liked to cobble wiring! (BIGGEST PET PEVE)... there is only one wire leading to the current blade style plug in. Digging deep here as I've not seen many of the factory auxillary fans on these trucks, but then again I'm a youngen... so I haven't worked on too many of em besides the 5 my family has owned.

HELP GUYS
Thanks in advanced!

Re: Auxillary Fan
 

I'm sorry, I don't think my first post was very clear.

I'm referring to a factory auxillary fan that is in front of the radiator and is set for cooling the radiator... hence the thermostat issue. The current thermostat supplies power at all times as opposed to when the coolant reaches a certain temperature like it's designed to.

Does that clarify?

Re: Auxillary Fan
 

ttt, nobody?

Re: Auxillary Fan
 

yup

Re: Auxillary Fan
 

There should be power to it all the time, but it is controlled by a fan switch in the passenger side cylinder head. When this switch sees the set temp, it closes the circuit and allows the fan to run. Could be either the PO wired directly to the battery and bypassed this switch, or it is bad and needs replaced. Your local auto parts store should carry or be able to get the proper switch. Try NAPA before anyone else if you have one close.

Re: Auxillary Fan
 

Correct. I'm aware of where the wire goes and where the switch is. I'm unaware of what the switch and plug are supposed to look like. As previously mentioned, they are currently just a blade style plug in with a single wire going to the switch on the passenger head. It does have power all the time, but the switch is not acting as it's supposed to but the parts store does not give me the same switch as the one that's in the truck currently when auxillary fan switch is looked up in there computers. So i'm currently at a loss.

Re: Auxillary Fan
 

this is the fan switch that the parts store sells me... but not the blade style switch that is in the truck. So if that is indeed the correct switch... which is basically what i'm asking... how do I go about getting the male end of this plug? And should there be two wires going to the male end or just one?

Re: Auxillary Fan
 

My C-30 is relatively un-molested. Though I'm having issues and the switch also needs replacing. (later) Mine had a small, plastic plug in on the end of the wire. Heat from the exhaust made it very brittle, so when it fell apart, I was left with a single wire with a small (1/8 " +/-) spade connector. Currently there is a small,single blade on the switch. I may be able to snap a pic tomorrow, to dark now.

Mine won't run until the key is turned (aux fan). It will run as long as the truck is. It's currently unplugged as the AC doesn't work and I don't need the fan.

Re: Auxillary Fan
 

Thanks a lot man. I'd appreciate it.

What you're describing could have happened to the plastic on my pieces as well as it is in a high heat location. Wouldn't surprise me at all! Look forward to checking out the pics.

Thanks for the responses guys!

Re: Auxillary Fan
 

Ok, I'll try posting a pic. I've been fighting an upload to photobucket and gave up. (uploading pics on dial-up, ugh.)

Doesn't show much to me, but it may help you out.

The flat blade is small, I plugged the wire back in for the photo op

Re: Auxillary Fan
 

Yup that's exactly what mine looks like as well. Just not what the one from the parts store looks like. But I suppose that's because of it melting the plastic casing like you mentioned with yours. Thanks!

Re: Auxillary Fan
 

If you don't mind me asking, what headers are you running? They look like long tubes!?! Any lift of the truck? Do the headers touch the leaf spring clip?

Re: Auxillary Fan
 

Anyone know how effective this auxillary fan is? The switch on our 86' C30 is broken - no tab left on the switch to hook anything to. Cannot find a replacement switch that does not cost an arm and a leg (~$69).

Wondering if it helps at all, especially under load at freeway speeds. I wouldn't think so but the front of the condenser/radiator is so blocked with stuff including this fan and engine oil cooler, maybe the vehicle needs all the help it can get?

(Did anyone notice cooler running temps after fixing their broken aux fan setup?)

Re: Auxillary Fan
 

I'm guessing that the aux fan only comes on when the air conditioning is on?
I could be wrong though, wouldn't be the first time.......

Re: Auxillary Fan
 

Might also come on when the AC is on, but it also comes on due to a temp switch in the right cyl head.

Re: Auxillary Fan
 

The only thing I fixed on mine was the constantly running. I still haven't fixed the ac (lack of $) but there is a relay on the ds fender that fell apart when I went to check the connection. Changed the relay and no run-on. Relay was far cheaper than the temp switch, iirc about 15$.

If your having problems at freeway speeds, look toward the rad or shrouding. iirc anything above 45mph, the fans are decoration. Air moving (while driving) provides the cooling.

Re: Auxillary Fan
 

Thought the same thing but looking at the frontal area being small, no air dam, and the gap between the front of the radiator core support and the bumper not being filled in, wondering if the air is deciding to bypass the front and go under the truck instead of through the radiator at speed.

(in other words, wondering if airflow is so bad on the freeway that we're essentially using the fans to always pull/push air through the radiator).

Shroud is good.

Re: Auxillary Fan
 

If I didn't have a stock fan come apart as a teenager, I might thing the same thing. (came apart due to damage by me or PO?)
The truck ran into problems when I got into the city, not the highway.
If GM has an issue, there would have been a recall to install fans, air dams, etc. Hundreds of thousands of these trucks without issue have run up and down the roads. Frontal area should be more than adequate.

Look at it realistically. Air will flow under. It will flow over. Air hitting square will flow to the path of least resistance, which is through.
I have had to cover a radiator that was over-cooling. Picture big trucks in the winter...

Re: Auxillary Fan
 

I don't know if they still do, but Summit use to carry the fan switch that is in the passenger head, it would come on at a lower temperature than the stock one.

The stock one in my '92 454 is designed to come on at 230 degrees or when the a/c is turned on if I remember right.

Re: Auxillary Fan
 

The factory wiring diagrams will have the AC-Delphi plug part number. You should be able to go from there.

Prolly adding a shop built heat shield would be a good idea.