93 Silverado blower issue

[brando50394]

Having a problem with my ac controls in my 93. I have high speed that feels like med . And low and med run at the same speed as low has me stumped new resistor and blower put in.

 

[AK49BWL]

High speed relay burnt out. Similar issue to another recent thread here, I'll see if I can find it.

Edit: https://www.gmt400.com/threads/ac-controls-fan-not-working-on-hi.67236/post-1415986

Actuators will NOT cause this issue. Have you replaced ANY of the relays? Switched connectors to the relays, see if the problem changes? It sounds like you might have a failed high-blower relay.

Relay positions per speed:
SPEED Relay 1 || Relay 2
Off: OFF OFF --> Power in to relay 1, out to relay 2, dead ends at relay 2 because relay 2 is off.
Low: ON ON -->Power in to relay 1, out to resistor pack, current flows through both resistors directly to blower - relay 2 is unused.
Med: ON OFF --> Power in to relay 1, out to resistor pack, current flows through ONE resistor and then to relay 2, from relay 2 to blower.
High: OFF ON --> Power in to relay 1, out to relay 2, from relay 2 direct to blower.

So if Relay 2 isn't working, you'll have the same speed on Low and Med, nothing on High, and removing the relay entirely from the circuit causes the system to go to low speed because relay 2 (in its default off state) allows current to bypass the second resistor. The resistor glows because there's 1: no airflow over it, and 2: With relay 2 off, current is flowing through the one resistor - Low and Med are not running the blower at max, but technically Med.

 

[brando50394]

High speed relay burnt out. Similar issue to another recent thread here, I'll see if I can find it.

Edit: https://www.gmt400.com/threads/ac-controls-fan-not-working-on-hi.67236/post-1415986

Nothing I have matches up to anything I seen cause I have 3 relays and a 5 wire resistor could I have the wrong controls in this truck. The one with the max button. Cause if I jump the 3 rd relay it will blow on hi. Also if I unplug the 2 pin wire on resistor it doesn’t change anything

 

[AK49BWL]

Ah, you're running the updated 4-speed system. Those were originally only in late 93s and most 94s. I'll have to take a look at my diagram and redo my table as it's slightly different. I can still say without much doubt the HI blower relay is dead tho, especially given that jumping it works fine.

Side note, it sure is clean up under there!

 

[brando50394]

Ah, you're running the updated 4-speed system. Those were originally only in late 93s and most 94s. I'll have to take a look at my diagram and redo my table as it's slightly different. I can still say without much doubt the HI blower relay is dead tho, especially given that jumping it works fine.

Side note, it sure is clean up under there!

Seems like the controller isn’t turning it on and only has the 3 speeds just says med low and high. Even in manual says it should have lo, med lo , med hi and hi

 

[AK49BWL]

Yes, it should, there's a wire that needs to be grounded at the head to enable it because those heads were used from 92+, but the 4th speed option didn't appear until late 93. Possible it wasn't hooked up or came loose.... OR, your head has been replaced with a very early version of the "dedicated recirc button" heads that doesn't work at all with the 4-speed setup... Which means you would need to find another head from a later truck and try it out.