I have replaced the heater control modual, ive.

Tiny
ANONYMOUS
  • MEMBER
  • 1996 CHEVROLET SUBURBAN
  • 207,000 MILES
I have replaced the heater control modual, ive replace the heater actuator but I still only get heat through defroster/ vents no heat to the floor also with heat turnedoff I still get heat coming out defrost / vents heat off blower off its not engine heat how can fix this
Wednesday, December 26th, 2012 AT 6:06 PM

10 Replies

Tiny
CHUCK WALKER
  • MEMBER
  • 7 POSTS
I have a similar problem. Replaced the control module and the actuators and the actuators don't seem to do anything no matter what I set the controls to.
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Monday, December 11th, 2017 AT 3:16 PM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
The common reason for that is that the controller has internal errors. You need to use a dealer or similar scan tool to check the climate control head for stored codes. It will also allow you to verify that the control head actually is functional. They can light up and seem to operate but not send control data to the actuators.
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Sunday, December 17th, 2017 AT 12:26 AM
Tiny
CHUCK WALKER
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  • 7 POSTS
Mine turned out to be a bad ground circuit to the actuators and the blower motor. Ran new ground wires to each of them and they all started working.
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Sunday, December 17th, 2017 AT 6:46 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
That is always fun. They like to tie grounds together and then put the ground connection right in a spot that gets water/dirt/salt around it so it corrodes and fails.
That is one nice thing with the scan tool you can watch the control voltages. If you see say 12 volts on one side of the actuator and the same on the "ground" side, you know the ground is open.
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Sunday, December 17th, 2017 AT 2:43 PM
Tiny
CHUCK WALKER
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  • 7 POSTS
Sadly mine is a 95 and is ODB1. No one has a scanner for it even if it did record that stuff. I found mine the old fashion way with a test light and on OHM meter. :-)
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Sunday, December 17th, 2017 AT 2:48 PM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
That same testing is how you find that issue on a 2018 so it isn't that old. :-)
You might be surprised what a scan tool can pull on OBD I systems.
But you found it without one.
Good job.
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Sunday, December 17th, 2017 AT 3:13 PM
Tiny
CHUCK WALKER
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  • 7 POSTS
If you know where I can get a scanner that would be awesome. Under certain conditions I get a check engine light and no one knows what the fault is.
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Monday, December 18th, 2017 AT 7:10 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
On an OBD I you can pull trouble codes with a paperclip. Not all of them but if it's stored it should show up.
https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

As for getting a scan tool, how much do you want to spend? For a pretty good unit you can get something like an OTC Genisys with OBD I and II coverage for around 5-600.00 on Ebay.
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Monday, December 18th, 2017 AT 8:07 AM
Tiny
CHUCK WALKER
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Yeah, they taught us the paperclip trick in school. I would love something with a digital readout but not willing to spend over $100 for it. It's ok. I love that it makes me solve problems through troubleshooting, which is more challenging. (Said no mechanic ever). Hahaha.
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Monday, December 18th, 2017 AT 9:17 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
That tool isn't one of the cheap ones. It is a full on real pro level device just not the latest and greatest, if you buy one with all the gadgets and latest updates you have a tool that covers just about every Domestic/Asian/European car/truck from the 80's through about 2012. It can do ABS, transmission, Scope, exhaust gas, and more. Not just reading the codes but showing live data, bi-directional controls, testing, and more.

As for troubleshooting. There are a lot of folks who believe in the "Test don't guess" methods.
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Monday, December 18th, 2017 AT 8:48 PM

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