CUTLASS No high speed on defrost/heat

S

Supremeone

Not-quite-so-new-guy
Feb 23, 2020
12
3
Toronto, Ontario, Canada
When I turn my defroster on to the high setting it turns off. It works on the other settings. I’m assuming it’ll be the fuse or relay? Does anyone have a diagram of which fuse and where the relay is?

Just got the car and am waiting for my manuals I ordered so I have no idea where anything is on these gbodies. Any help is appreciated.
 
fleming442

fleming442

Geezer
Dec 26, 2013
9,276
113
The high speed blower relay is mounted to the heaterbox (under the hood) near the blower motor and resistor. The most common problem is the 4 wire plug melting (under the heater core hoses, near the firewall). There is a 12ga. red that feeds off a fusible link to the relay. The plug wasn't designed to carry enough current, melts, and causes a high resistance open. Start there, and if that's not it, move to the fusible link at the starter.
 
B

bracketchev1221

G-Body Guru
Jan 18, 2018
578
93
The high speed blower relay is mounted to the heaterbox (under the hood) near the blower motor and resistor. The most common problem is the 4 wire plug melting (under the heater core hoses, near the firewall). There is a 12ga. red that feeds off a fusible link to the relay. The plug wasn't designed to carry enough current, melts, and causes a high resistance open. Start there, and if that's not it, move to the fusible link at the starter.
Isn't the high speed separate of the relay? I am not an expert on G-body wiring, but mine had an issue where it lost high speed and it was a plug that ran over the top of the valve cover. If I wiggled it I got high speed. All the low speeds ran through the relay on the fan box.
 
69hurstolds

69hurstolds

Comic Book Super Hero
Supporting Member
Jan 2, 2006
3,651
113
My bet is the 4-wire plug, and then maybe the relay. The relay is GM p/n 10018449. Sometimes you'll see the p/n stamped in yellow or black ink right on the relay casing with a big "C4" on them. Factory installs and early replacements had the inked ones. It's hanging off a bracket bolted to the blower motor casing in front of the resistors. Remote chance it's the fan switch on the dash.



If you're 4 wire plug has melted and have a bad connection there, you have two options...

Free + a little electrical tape: Remove plug and re-connect the wires and tape around them. Kind of a jury-rig and will look like azz, but it will work.

For $7.87 plus tax, you can get a new connector:

https://rover.ebay.com/rover/1/711-...0001&campid=5335822911&icep_item=381822347225

4-wire blower relay connector.jpg
 
S

Supremeone

Not-quite-so-new-guy
Feb 23, 2020
12
3
Toronto, Ontario, Canada
Checked everything out and it seems to be the relay. The plug was in excellent condition. Ordered the relay from the local parts store and of course they send a resistor lol. Reordered the correct part for me so should have it by tomorrow.

Thanks again for everyone’s help.
 
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