heater a/c fan not working on high

i have a 1997 chevy truck 4x4 with the 5.7 engine the high speed doesnt work on the fan, replaced the blower motor resistor. could it be the switch or a vacuum line? or something else any help appreciated thanks john

i have a 1997 chevy truck 4x4 with the 5.7 engine the high speed doesnt work on the fan, replaced the blower motor resistor. could it be the switch or a vacuum line? or something else any help appreciated thanks john
What size truck?

High blower speed is run threw a high blower motor relay and fuse.

Is relay and fuse good?

its a 1500 series.. i havent checked the fuse yet is it under the hood or dash? and also where might the relay be located right by the resistor? there is one there. not sure which is for the high speed on the blower
thanks but i'll check the fuses now

its a 1500 series.. i havent checked the fuse yet is it under the hood or dash? and also where might the relay be located right by the resistor? there is one there. not sure which is for the high speed on the blower
thanks but i'll check the fuses now

Fuse is in under hood box.
50 amp MAXI fuse.
Relay is on top of ac/heater housing under hood.
Post back whatyou find there.

found a blown 50 amp fuse have to go get one.. any idea what may have caused it to blow? or just normal wear

found a blown 50 amp fuse have to go get one.. any idea what may have caused it to blow? or just normal wear

Fuse do not have normal wear.
Over load blows them.
What fuse was it?

The ac fuse is fuse no. 3

If it blows again better check fo shorts and amp draw on that circuit.

advance had only one fuse.. put it in and it blew right away. now what to do to find what is shorting it out

To save on fuses get a circuit breaker and hook it up to that circuit.
Look all wiring and plug ins over for shorts or grounded out.
I would unplug blower motor to start with and seen if that takes care of short.
If not start checking or unplugging other stuff in that circuit.

great thanks i'll give that a try see how easy it is to track down now

The wiring diagram shows that fuse feeding high blower motor relay.

If still shorts with blower motor unplugged try unplugging or switching blower motor relay.
A bad relay could short to ground.
Good Luck
And let us know how it goes.

unplugged the blower motor relay and resistor one at a time untill all 3 were unplugged and still sparks when i put the circuit breaker in. where can i find the wiring diagram and where else might i look thanks again for any help

unplugged the blower motor relay and resistor one at a time untill all 3 were unplugged and still sparks when i put the circuit breaker in. where can i find the wiring diagram and where else might i look thanks again for any help

Factory repair manual or
http://www.alldata.com/products/diy/index.html
or Mitchell on demand online DIY sub.

ok found the problem the wire from the fuse box to the to fire wall was bad somewhere i didnt unwrap it just cut the two ends and ran a new wire from the fuse box to inside under the dash. had checked the switch earlier had a friend who had one so we swapped to see if that was it.. but to no avail. so it was just running a jumper wire with a circuit breaker to see where i might avoid the short. finally after hours of searching and playing thanks for all the help

You are welcome and thanks for posting back the fix and how it went.
Good luck