# 1991 Chevy Suburban (Weird Heat Problem) **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** chevrolet, suburban\ **Created:** [February 5, 2017, 12:50am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481 "2017-02-05T00:50:48Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 12:50am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/1 "2017-02-05T00:50:48Z")
Guys/Gals, I have a really strange problem with the heating in my 91’ Chevy Suburban. For some reason, the heat will not work when I close the hood. I’ve burped and flushed the radiator, heating core, checked the blend doors/actuators, you name it. The only other thing I can think of that it might be, is the thermostat. Any ideas as to what to do and why the heat works when the hood is open, but not closed? Thank you! ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [February 5, 2017, 1:03am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/2 "2017-02-05T01:03:22Z")
Make sure a hose between the engine/heater core isn’t being pinched off by a hood hinge when the hood is closed. Tester ---
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 1:13am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/3 "2017-02-05T01:13:30Z")
I don’t see any hoses that look like they’re getting pinched when the hood is closed… ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 5, 2017, 1:15am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/4 "2017-02-05T01:15:41Z")
A mystery to be sure, is there an under hood light that goes on when you open the hood? ---
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 1:20am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/5 "2017-02-05T01:20:07Z")
Not when I open the hood. There is a light that I can turn on though when the engine is running. I even disconnected the sensor that gets engaged when the hood is lifted/closed to see if that would somehow do something but no luck. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 5, 2017, 1:31am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/6 "2017-02-05T01:31:37Z")
Just thinking there is a backfeed that supplies power to the blend doors to provide heat when the hood is open. ---
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 2:06am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/7 "2017-02-05T02:06:08Z")
If there is, I cannot find it… I’ve looked everywhere, with the hood in different positions, to try and locate some kind of hose or electrical switch that is being engaged when the hood is down with no success. The only button that I can locate is one on the driver’s side. However, it makes no difference if that is connected or not. The heat still only runs when the hood is up. I’m out of ideas. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 5, 2017, 2:19am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/8 "2017-02-05T02:19:42Z")
Hood open Indicator? Have you checked the fuses and relays? ---
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 2:21am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/9 "2017-02-05T02:21:39Z")
I’ve checked the fuses… Not sure where the relays would be though. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [February 5, 2017, 6:39am UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/10 "2017-02-05T06:39:33Z")
What is the heater temperature output with the hood open and closed? ---
**Author:** ![stvnedmon](https://avatars.discourse-cdn.com/v4/letter/s/d26b3c/32.png) [@stvnedmon](https://community.cartalk.com/u/stvnedmon)\ **Post date:** [February 5, 2017, 2:44pm UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/11 "2017-02-05T14:44:08Z")
Not sure of exact numbers. However, when the hood is closed, it is blowing cold air, no heat at all. When the hood is open, there is typical heat. ---
**Author:** ![Salc00](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@Salc00](https://community.cartalk.com/u/Salc00)\ **Post date:** [February 5, 2017, 3:32pm UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/12 "2017-02-05T15:32:37Z")
If it is a dual heater model 6.5 diesel, I had a similar problem caused by the plastic water flow splitter just behind the motor close to the firewall. There are two of them. The plastic had become soft and flattened at the hose coming from the motor when pressure changed. I made two new splitters out of copper pipe tees and pipe reducers since hose sizes are different, and silfloss brazed them together rather than 50/50 solder. My problem went away after that. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [February 5, 2017, 3:35pm UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/13 "2017-02-05T15:35:43Z")
How would the splitter be effected by hood open or closed? ---
**Author:** ![Salc00](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@Salc00](https://community.cartalk.com/u/Salc00)\ **Post date:** [February 5, 2017, 8:49pm UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/14 "2017-02-05T20:49:53Z")
Engine bay temperature rises when the hood is closed apparently just enough to make the plastic splitter soft enough to partially collapse. I also separated the two splitters that were touching from the factory. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [February 5, 2017, 9:01pm UTC](https://community.cartalk.com/t/1991-chevy-suburban-weird-heat-problem/99481/15 "2017-02-05T21:01:32Z")
I have run into some weird issues on GM, One I put a socket in for a spotlight, if the spotlight was plugged in backfeed from the spotlight with a chargeing circuit caused the engine to keep running when the key was turned off. My thought was it is an electronic control for the heat, fuse or relay out but for whatever reason if a light was being powered when the hood was raised it provided juice to the heat control via backfeed.