Working on my 1988 Jimmy Sierra classic

[Andrew Hare]

I’ve been having some issues with the HVAC in my 1988 Jimmy. The heat works only when it wants to, I’m in the process of going thru a messy divorce and my soon to be ex threw my service manual in a box when she threw me out of the house last December. Does anyone have a good wiring diagram the could E-Mail me a pic of? I need to get this issue resolved before it gets down in the 30’s any help would be greatly appreciated.

 

[Wes Harden]

What are the symptoms when it is acting up? I am assuming the fan is not working, because you are asking for electric diagrams. Rpo code will help, sticker glove box, will be 3 digit alpha numeric c6? Little more info and we can get you warmed up

 

[Andrew Hare]

Basically it works when it wants to all of my vacuum stuff operates the electrical portions of it only work intermittently

 

[Andrew Hare]

I am currently at work so let me get thru the day and I will check the sticker on the glove box and let you know what I find I will also post a picture of my RPO code label when I get a chance, I mis my heat in my truck it’s only got two settings Hot and Broil

 

[Andrew Hare]

What are the symptoms when it is acting up? I am assuming the fan is not working, because you are asking for electric diagrams. Rpo code will help, sticker glove box, will be 3 digit alpha numeric c6? Little more info and we can get you warmed up

You are correct, the fan isn’t working but I’m still getting hot air coming from the vents so I know my heater core isn’t clogged. Just no blower motor at all

 

[swettysblazer]

Check the blower motor resistor (I honestly forget if these trucks have one) or the plug on the heater box and check your ground.

 

[Andrew Hare]

Check the blower motor resistor (I honestly forget if these trucks have one) or the plug on the heater box and check your ground.

I know when it’s working I have all of my blower speeds, I will have to check my grounds too.

 

[Andrew Hare]

Check the blower motor resistor (I honestly forget if these trucks have one) or the plug on the heater box and check your ground.

Do you know where the plug on the heater box is? Is it under the dash or the hood?

 

[swettysblazer]

Do you know where the plug on the heater box is? Is it under the dash or the hood?

Under the hood right on the heater box.

 

[Wes Harden]

Under the hood pass side, top of ac evap core plenum box, there is also a hi speed blower relay very close to it.
I suspect the power wire at the blower it self, a spade connection. Inspect this connection,make it is clean and tight. That the spade in the blower motor half is firmly in place and doesn't wiggle. The plastic insulation is not melted. Purple wire @12 gauge.
The resistor block has 4 wires in 1 plug, they get very dirty and way to much resistance. Unplug hit with contact cleaner, very flammable use caution, wire tooth brush the male spades plug it back in. Test results.