1971 Vette high speed fan operation question.

[Rick Church]

I seem to remember reading somewhere in the past year about some relay or switch that enables the high speed position on the blower switch to function. Before I detailed the engine compartment of my car (1971 Vette), the fan would blow well on the highest postion on the switch (air conditioning on or off). Now when I go the the "high speed" (highest) position on the fan switch the fan stops. Positions 1, 2 and 3 work but the top speed dosesn't. Can somebody fill me in on this one?

Thanks, Rick in Tennessee

[Ed Jennings]

Re: 1971 Vette high speed fan operation question.

There is an in-line fuse for the high speed wiring. It is located in the engine compartment in the vicinity of the wiper motor, between the wiper motor and the fan motor. (Not connected in any way to the wiper motor, just in that general area). The fuse is likely blown.

[Dave S.]

Re: 1971 Vette high speed fan operation question.

Rick,

As I read you post I can see you need to purchase the NCRS 68-72 Operations Manual. It is designed to explain each and every operations function and is used a the "Bible" for the Performance verification. Among many other things it will answer your question on the heater switch operation. I believe it is around $15 and well worth it.

[Rick Church]

Re: 1971 Vette high speed fan operation question.

Great Dave, where do I buy it? Shoot me an emial at CW5Church@aol.com

[Jack H.]

Also....

4-sp fan comes with A/C option. Typical reasons for lack of highest speed while other lower speeds work are:

(1) Control relay mounted to Harrison air box in the engine compartment is 'fried' with respect to its HI mode.

(2) Separate in-line fuse off the horn relay is blown or not making good contact.

(3) Center console switch is faulty.

I've put these in order of frequency of occurence based on years in the shop with 1=high probability to 3=low probability. Looking at your AIM book for '71, you should note two separate PN's called out for the engine compartment control relay. One was a Delco Remy part and the other was a secondary outside supplier. The Delco relays have long been discontinued and, in my experience, are more prone to failure.

You can go to NAPA and get a functional replacement (the can won't look exactly the same, but it'll bolt on and hook-up A-OK) for a very reasonable price (something like $5). So, check the #2 (fuse) first because that's a no brainer and if good, try replacing the relay. I'll bet you smile minutes after changing the relay.

BTW, if your car has the Delco version of the relay, do NOT discard it! Sometimes, these can be 'saved' by removing the cover (simple crimp) and gently cleaning the contact surfaces....

[Rick Church]

I found the problem with the high speed position!

The orange wire that goes from the horn relay, through the in-line fuse, and then to the relay, had pulled out of the plug fitting at the relay. It seems there are two orange wires that go to the same contact for the high speed fan relay contact. Now I just need to figure out a way to put the wires back in the plug fitting and get them to stay. Thanks for all the great information guys!!

[John H.]

Re: I found the problem with the high speed positi

Rick -

If memory serves me correctly, that power feed wire has a spade terminal on the end that goes under one of the screw connections (battery power bus) on the horn relay; it doesn't "plug into" any cavity on the bottom.