76 Blower motor

[Ed P.]

OK I have a 76 with air that the blower only works on the lowest settings. It seems to work fine til you select max then it shuts off. Any suggestions. Ed

[Joe L.]

Re: 76 Blower motor

OK I have a 76 with air that the blower only works on the lowest settings. It seems to work fine til you select max then it shuts off. Any suggestions. Ed

Ed----


Does the car have A/C? If not, the first thing I'd try is to replace the blower motor resistor. It's GM #3929052 and it's still available.

[Ed P.]

Re: 76 Blower motor

Yes the car has A/C

[Joe L.]

Re: 76 Blower motor

Yes the car has A/C

Ed----


In that case, try resistor GM #6262652. About 23 bucks, GM list.

[Ed P.]

Re: 76 Blower motor

Can I bypass the resister to check if blower will run on high. Trying to fix tonight. Ed

[Joe L.]

Re: 76 Blower motor

Can I bypass the resister to check if blower will run on high. Trying to fix tonight. Ed

Ed-----


I don't know if that will work or not. Hopefully, others will.

[Ed P.]

Re: 76 Blower motor

Well I just went out to the car and I have to change my description a little. With the blower set on off the blower runs on low. The next couple of settings the blower runs faster. When you select [HI blower setting] it shuts off. So I am wondering if bubba has been wiring my switch. I went and looked at a buddys 76 vette and his does not work at all so when I figure this one out I will have to fix his also. Ed

[Robert S.]

Re: 76 Blower motor

I had this problem on my son's 74' with AC about 10 years ago. I checked the wiring diagram and saw that there is a fuse in the input for the high speed position only. The fuse is in the middle of a wire run and is located up near the firewall on the engine compartment side and sort of tucked up out of sight in the corner, but I cannot recall if it is drivers side or passengers side. At any rate it did not take long to find the line with the fuse in it. A quarter turn of the fuse holder and it comes apart, in went a new fuse of the same capacity and it is still working on high 10 years later.
I understand this is a fairly common problem. I have no idea what blows the fuse but at least in my case it certainly did not appear to be a short to ground anywhere. I think you will find you have the same problem and it will cost you maybe 50 cents to fix and about 5 minutes time.

[William C.]

Re: 76 Blower motor

A couple of things, "off" is a relative term in the cars without side window vents as the fan in "off" position runs at low speed to pressurize the cockpit slightly to help the "flow thru ventilation work. Secondly. there should be a rely for high blower, it will be in the electrical diagram in either the AIM or a service manual. You can jump the high blower relay to check the blower. If the blowe5r works on low and intermediate speeds, usually either the fuse or the relay are at fault.

[Joe L.]

Re: 76 Blower motor

Ed-----


The high blower cutoff relay is currently GM #89057581. It GM lists for about 25 bucks. If the one you take out is marked 463468, then the 89057581 is the one you need.

[Jack H.]

Re: 76 Blower motor

There are generally two causes for this malady (4-speed AC blower motor won't run on Max speed but will run at the lower speeds).

(1) The in-line fuse for the blower motor's hi speed operation (typically connected to the side bar engine compartment B+ buss of the horn relay on earlier Sharks) is history.

(2) The heater blower motor relay that switches power to the various terminals of the heater blower motor resistor network (network is bypassed in MAX mode) has failed and/or has a VERY dirty/worn relay contact underneath the cover...

Can you jumper power directly to the blower motor to test it? CERTAINLY! That's how motors are bench tested, running raw B+ to them to force MAX speed operation.

[Ed P.]

Re: 76 Blower motor

OK thanks guys that helps. I have looked high and low for this fuse and cannot find it. Ed

[Patrick H.]

Re: 76 Blower motor

OK thanks guys that helps. I have looked high and low for this fuse and cannot find it. Ed

Ed,

The white fuse holder at the lower right corner of the picture (on a 71, at least).

Patrick

[Jack H.]

Re: 76 Blower motor

Pat is telling you how/where the in-line fuse is located on early Shark cars. You have a later model where the design of the horn relay changed and it was moved from the engine compartment into the cockpit thus there is no side buss bar on the horn relay for the engine electrical system to grab B+ power from.

But, while the location of items and their wiring changed, the same circuit topology continued with a discrete power source for A/C equpped cars to run the blower fan in high or MAX mode. Here's the circuit schematic for the '76 Corvette's A/C system with the inline fuse highlighted.

Now, it's your job to go crack a book and find where the inline fuse is located on your car. Sometimes this is covered by the owner's manual other times you have to go to consult the shop manual.

[Ed P.]

Re: 76 Blower motor

Guys thanks for all your help. This morning I started trouble shooting starting at the blower. I proceded to the relay, and I have switched power to relay. So I replaced relay and all is well. Never found that dam fuse but I will, and will post its location. Thanks Ed