K5 blower motor question

[77k5blz]

I bought a 77 k5 a while in need of work there wasnt a blower in the housing I just put one in and as soon as I turn the key on it blows on low even with the selector for vent def heat etc... Off. Is this normal or do I have a problem thank you ahead of time.

 

[dyeager535]

Normal. Part of the "flow through ventiliation".

 

[Massacre-77]

is thare a way to by pass this? it blows hot air on me in the summer

 

[dyeager535]

I'd say swap in a later heater control head, I believe they interchange, and I think that is how that setup was run, with the lower position on the early switch still sending power to one of the resistors on the fan housing.

I suppose you could just kill the lower heater position on the switch too, but that might get annoying. The later heavy duty and AC control heads I *believe* had one more switch position, the bottom-most being an actual off position.

 

[Massacre-77]

what year would work for a 74? thanks..

 

[77k5blz]

Thanks guys!

 

[dyeager535]

I *think* '73-91 all bolt in, but I'm not really that up on the '73-80 stuff.

 

[diesel4me]

Most all 73-87 GM trucks had the heater blower wired as such to be on "low" speed even with the switch in the off position...as Dorian stated,their "Flo-Thru Ventilation" package with the vents in the doors worked in conjunction with the blower motor to provide constant fresh air into the cab without an annoying breeze (supposedly)....................................................................................................................................................................................................I found it irritating to have the blower come on instanly on an icy winter morning,and blow a frigid breeze on me,and it also would "scream" sometimes and scare me silly,thinking a bearing seized up in my engine!........so...a few minutes with my test lamp isolated the low speed power wire on the blower motor resistor on the firewall,and one quick *snip* of the side cutters silenced the squeaky screamy blower motor until I turned it on to medium or high speed,like it should have been "factory"...if you still want low speed you could snip the wire for low speed and put a toggle switch in line with it to "kill" low speed when desired...

 

[dyeager535]

Just for clarification, are you sure any of the later ones (1981-ish?) were wired that way? My setup is the HD heater, so it's different anyways, but I thought that on all the later heater setups (HD Heater, AC, and standard) the bottom position of the fan speed switch was "off"?

 

[4xcrazy]

Both my '87 and '89 Burbs turn completely off in the off position of the switch.

 

[diesel4me]

My '82 K2500 stayed on low speed constantly with the switch off,so did my 77 GMC and 79 C10 Bonnanza I had...I'm pretty sure my 85 Suburban doesn't run the blower on low though,when its "off", its OFF--that has factory A/C,none of my other trucks did,so I bet ones with A/C or a HD heater might be wired differently................................................................................................my 81 G10 van has no A/C ,but I dont recall the blower being on low speed in the off position ,strangely enough,because the wiring harness in it is darn near identical to a pickup,even the same color codes...it does have a "hi output" heater core however,it had a straight six originally and the heater would drive you out if you left it on hi for long--I think my Burb has the high output heater core also...it too feels like it could heat a home!..

 

[77k5blz]

My 77 has ac and its on all the time or is it later ones with ac that it didnt run all the time?