No Heat issue

twodub · 10-27-2009, 06:37 PM

Hey guys, looking for some suggestions/help here. I have a 1993 GMC Sonoma 2.8, that the heater core started leaking massively last winter, so I replaced it today. I actually had the truck parked all summer until I could get around to it. While the core was leaking, my heat still worked, but with obvious problems. Now that I put the new core in, there's no fan or blowing, and I am not sure why. Antifreeze gets in/out of the core and it gets hot, and when I select heat or defrost I can hear the sound acknowledging it, and seems to work fine, but no air moves. The selector for the heat, Lo - - HI, doesnt seem to do anything. The trucks temperature is fine when I drive it, no signs of a stuck thermostat, that I can see. Do you guys have any advice for troubleshooting or had any similar problems? Thanks for any help you can offer.

scavanger · 10-27-2009, 06:47 PM

Did you leave the resistor unhooked ? Or maybe damage it while working on the heater ?

Scav.

twodub · 10-27-2009, 06:55 PM

The only electrical I can recall deal with was the connection to the blower motor, which I plugged back in after connecting the new heater core to the hoses. I checked it, so I dont think its that. It seems almost too coincidental timing-wise for it to be the switch I would think.

scavanger · 10-27-2009, 07:17 PM

Did you check fuses ?

Scav.

leolkfrm · 10-27-2009, 07:25 PM

should have been another connector with about 7 wires

twodub · 10-27-2009, 07:27 PM

That I did not, will do that for sure. One quick question, it might be a stretch tho, I haven't placed the heater core cover, vent, and facing back on yet, that wouldn't be causing any issues would it? Is there any kind of sensor or something that would prevent it?

twodub · 10-27-2009, 07:34 PM

Quote:

Originally Posted by leolkfrm

should have been another connector with about 7 wires

For the heater core? I didnt mess with anything going to the heat control head. I looked over what was visible, couldnt see anything unplugged. I guess by loosening up the dash I could've pulled a connection loose, but I checked and couldnt see any.

crabtruck · 10-28-2009, 02:41 AM

Welcome to the forum twodub.

This is not like a washer that you must have the lid closed to run.

As scav mentioned you should check fuses to be sure something didn't short
during the process.
The resistor that he and leo are talking about is not in the head by switch,
it is mounted on or in the duct by blower in most trucks.

You said you heard the heat/def change happening but is that electrical ?
Vac or cable? I think the temp selector is electric though, hear that ?

Since no speeds work, I would first suspect disconnected ground.
It could easily be the "input side" of this also so check the above harness.
You could start following wires from blower and just keep going back to head.
It's pretty clear when you get to connections. Don't forget fuse.

This shows general "where" of resistor(s) and has relays yours may not.
.

scavanger · 10-28-2009, 04:57 AM

crabtruck's post made me think of something. On some heater motors it is possible to install the plug so it don't make connection. Espesially if it has the two wire connector.
Check the wire at the motor for power.

Scav.

twodub · 10-29-2009, 03:38 AM

Thanks for the advice guys, gonna try to free some time up from work to really work this out. I'm gonna try what you recommended, hopefully today, and I'll report back with what I find. Thanks for all the info so far

10-27-2009, 06:37 PM	#1
twodub Junior Member Join Date: Oct 2009 Posts: 5	No Heat issue Hey guys, looking for some suggestions/help here. I have a 1993 GMC Sonoma 2.8, that the heater core started leaking massively last winter, so I replaced it today. I actually had the truck parked all summer until I could get around to it. While the core was leaking, my heat still worked, but with obvious problems. Now that I put the new core in, there's no fan or blowing, and I am not sure why. Antifreeze gets in/out of the core and it gets hot, and when I select heat or defrost I can hear the sound acknowledging it, and seems to work fine, but no air moves. The selector for the heat, Lo - - HI, doesnt seem to do anything. The trucks temperature is fine when I drive it, no signs of a stuck thermostat, that I can see. Do you guys have any advice for troubleshooting or had any similar problems? Thanks for any help you can offer.

10-27-2009, 07:25 PM	#5
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,300	should have been another connector with about 7 wires __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

10-28-2009, 02:41 AM	#8
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,366	Welcome to the forum twodub. This is not like a washer that you must have the lid closed to run. As scav mentioned you should check fuses to be sure something didn't short during the process. The resistor that he and leo are talking about is not in the head by switch, it is mounted on or in the duct by blower in most trucks. You said you heard the heat/def change happening but is that electrical ? Vac or cable? I think the temp selector is electric though, hear that ? Since no speeds work, I would first suspect disconnected ground. It could easily be the "input side" of this also so check the above harness. You could start following wires from blower and just keep going back to head. It's pretty clear when you get to connections. Don't forget fuse. This shows general "where" of resistor(s) and has relays yours may not. . Attached Thumbnails

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10-27-2009, 06:47 PM	#2
scavanger Senior Member Join Date: May 2007 Posts: 262	Did you leave the resistor unhooked ? Or maybe damage it while working on the heater ? Scav.

10-27-2009, 06:55 PM	#3
twodub Junior Member Join Date: Oct 2009 Posts: 5	The only electrical I can recall deal with was the connection to the blower motor, which I plugged back in after connecting the new heater core to the hoses. I checked it, so I dont think its that. It seems almost too coincidental timing-wise for it to be the switch I would think.

10-27-2009, 07:17 PM	#4
scavanger Senior Member Join Date: May 2007 Posts: 262	Did you check fuses ? Scav.

10-27-2009, 07:27 PM	#6
twodub Junior Member Join Date: Oct 2009 Posts: 5	That I did not, will do that for sure. One quick question, it might be a stretch tho, I haven't placed the heater core cover, vent, and facing back on yet, that wouldn't be causing any issues would it? Is there any kind of sensor or something that would prevent it?

10-28-2009, 04:57 AM	#9
scavanger Senior Member Join Date: May 2007 Posts: 262	crabtruck's post made me think of something. On some heater motors it is possible to install the plug so it don't make connection. Espesially if it has the two wire connector. Check the wire at the motor for power. Scav.

10-29-2009, 03:38 AM	#10
twodub Junior Member Join Date: Oct 2009 Posts: 5	Thanks for the advice guys, gonna try to free some time up from work to really work this out. I'm gonna try what you recommended, hopefully today, and I'll report back with what I find. Thanks for all the info so far