a/c won't work on high

[redwolf]

I've been looking around but can't find a answer to this problem. It's a 84 k10 that when i put the a/c on high it cuts out. I replaced the blower motor relay and blower resisitor and still the same. At the relay i checked with a tester and when i put it on high the orange wire powers up but nothing comes out to the blower...i've already changed it out twice thinking that it was defective....any ideas?

[pontgta]

Make sure you have a good ground. will look at the schematic later, but check power to good ground, then at 12v directly to motor to make sure it works good.

[hatzie]

AC Compressor clutch is not engaging or blower isn't running on high?

If the blower isn't working check the blower relay.

[redwolf]

it's the blower that doesn't work on high. i used a jumper wire from the orange to the purple and it works... what gound are u talking about? is it the one from the blower?

[grs]

Maybe the switch is bad.

[redwolf]

how can i check the switch to see if its bad or not?

[pontgta]

believe on the switch..
tan is low
lt bl is med
dk blu is med 2
....brn wht high???

Yes the ground on the motor....

where did you jumper? purple and oranage? on the relay?

orange and black look to be the coil. on the relay

[redwolf]

i jumped it on the relay

[redwolf]

i diconnect the selector switch inside and it still blows on low...is that suppose to happen?

[INSIDIOUS '86]

Should be a vacuum line connected to the motor to control some of the ducting and let's the motor go to high for some reason
Posted via Mobile Device

[redwolf]

i've checked the vacum lines already.....when i put it on high the relay makes a clik
noise and prevents power to the blower...on the resistor all the connectors have power on high only..

[bowtiemanchevyman]

there is a switch on the back of the control panel that the a/c. you can get on at classicparts the part number is 68-335 if its not working right the heart will not work right.

[motornut]

some are wired for the air to always "flow"
i cut the brown in my 79 to have an off(i have heat only)
you may need to replace the motor resistance coil - arrow -
prob find one broke

[anson0487]

my 84 crew cab is doing the same thing, high on blower cuts out when i hit a bump. 1,2 & 3 work fine. iv checked the resistor coil and it looks fine, i guess ill put a diffrant swich in the dash an see if that fixes it.

[hatzie]

Originally Posted by redwolf

it's the blower that doesn't work on high. i used a jumper wire from the orange to the purple and it works... what gound are u talking about? is it the one from the blower?

The switch is OK because the ORANGE wire is hot on HI. Don't jumper the Orange wire to the Purple wire for very long. Full motor current will melt the blower switch (that's why the relay is there)

Your relay isn't switching volts to the blower with the switch on HI because;

• the RED wire from the firewall junction block isn't hot
• the BLACK ground to the coil is not making contact... CHECK THIS ONE!!
• or the relay is dead... hopefully the new part is OK

The blower relay is a high amperage SPDT relay that works as follows.

• Blower switch HI.

At the relay ORANGE (from the blower switch) and RED should be hot. This is supposed to close the relay contacts between RED (+12v Directly from the firewall junction block) and the PURPLE (blower motor hot).

• Blower motor switch in LO, M1, & M2

At the relay RED should be hot. DARK BLUE should have lower than 12v because of the resistors in the circuit. The relay contacts are in the rest position closing the relay contacts between DARK BLUE (blower resistor output wire) and the PURPLE (blower motor hot)

Switch positions & Resistor Pak. Note: The volts (less than 12v) at the DARK BLUE wire increase as the number of resistors decreases.

• LO Feeds power through R3, R2 & R1 to the DARK BLUE wire from the resistor pak to the relay. The at-rest contacts pass the power to the PURPLE motor power wire.
• Medium1 Feeds power through R2 & R1 to the DARK BLUE wire from the resistor pak to the relay. The at-rest contacts pass the power to the PURPLE motor power wire.
• Medium2 Feeds power through R2 to the DARK BLUE wire from the resistor pak to the relay. The at-rest contacts pass the power to the PURPLE motor power wire.
• HI Feeds the ORANGE coil wire on the blower relay closing the relay contacts between RED 12v and the PURPLE (motor feed) bypassing the resistor pak completely.

Hope this helps.

[redwolf]

ok, so i replaced the switch selector, resistor, and the relay...and it's still the same. But, i did notice that i have no power from the red wire at the relay on high...where does that red wire come from?? When you say from the "junction block" do you mean from the fuse box inside?

[f.monroe]

GM had problems back in the day. The blower gets full voltage on high. There used to be a blade connector on the firewall on GM cars and trucks that would burn inside the connector. Trace the wires and look for a connector. I know I repaires these on many cars so I assume that the trucks have them somewhere also. I can look at one of my trucks whel I get home to see if I can find the connector I am referring to.
Frank

[hatzie]

Originally Posted by redwolf

ok, so i replaced the switch selector, resistor, and the relay...and it's still the same. But, i did notice that i have no power from the red wire at the relay on high...where does that red wire come from?? When you say from the "junction block" do you mean from the fuse box inside?

You found your gremlin. The RED wire should always be hot regardless of fan or ignition switch position.

The Junction Block is the main electrical feed block on the firewall in the engine compartment with a stack of red wires on ring terminals.

[redwolf]

Thanks guys...it was the connection at the junction block. I just unscrewed and cleaned it up (alot of crusty plastic) and bolt it back up....and now the high selection works..thanks Hatzie.

[hatzie]

Good to hear it was so easy to fix. Stay cool.