C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

'84 no heat

Thread Tools
 
Search this Thread
 
Old Nov 21, 2017 | 03:04 PM
  #1  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default '84 no heat

Put new T'stat in 2 weeks ago. getting colder so heat would be nice.

I get no heat when I move lever to select heat. But if I leave lever to off and heat all the way to hot, I can feel some heat coming in. But I can not turn fan on as it will dilute the heat and blow cold.

Anything speciai I should look at ?
Reply
Old Nov 21, 2017 | 03:18 PM
  #2  
belairbrian's Avatar
belairbrian
Melting Slicks
Liked
Loved
Top Answer: 1
Top Answer: 3
 
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
Default

with heat mode selected and fan on where is the air coming out?


Are both hoses to the heater core hot?
Reply
Old Nov 21, 2017 | 03:56 PM
  #3  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default '84 no heat

Originally Posted by belairbrian
with heat mode selected and fan on where is the air coming out?


Are both hoses to the heater core hot?


Air comes out on floor. I'll have to get it hot to check hoses.
Reply
Old Nov 21, 2017 | 04:34 PM
  #4  
Tom400CFI's Avatar
Tom400CFI
Team Owner
Pro Mechanic
20 Year Member
 
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Default

Sounds to me like the cable from the temp slider lever has come disconnected from the lever or the crank arm on the heater box end.

I had that happen on my '92 recently; the crank arm actually popped up and out of the box, off the blend-door shaft. The crank arm was just laying on top of the heater box.
Reply
Old Nov 21, 2017 | 04:48 PM
  #5  
belairbrian's Avatar
belairbrian
Melting Slicks
Liked
Loved
Top Answer: 1
Top Answer: 3
 
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
Default

I thought the 84s had a valve in the heater hose that could shut off hot water flow to the heater core.


There not like our constant flow 92s
Reply
Old Nov 21, 2017 | 06:16 PM
  #6  
Tom400CFI's Avatar
Tom400CFI
Team Owner
Pro Mechanic
20 Year Member
 
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Default

Good point.
Reply
Old Nov 21, 2017 | 06:34 PM
  #7  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default

Originally Posted by Tom400CFI
Sounds to me like the cable from the temp slider lever has come disconnected from the lever or the crank arm on the heater box end.

I had that happen on my '92 recently; the crank arm actually popped up and out of the box, off the blend-door shaft. The crank arm was just laying on top of the heater box.

Just drove it. Heat is getting to the heater box as there was heat in the cabin, so both hoses were hot. Have a 200 deg. T'stat in it. Ambient temp is 50 deg. and cabin was getting plenty warm with selection lever off and heat set to 1/2 way to full hot.

I'll have to look closer at it this weekend when it gets near 60 here in NC.
Reply
Old Nov 21, 2017 | 10:28 PM
  #8  
Hot Rod Roy's Avatar
Hot Rod Roy
Safety Car
15 Year Member
 
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Default

'84 heater control is pretty simple (as should be expected in a "basic" car). With the temp slider (bottom lever) full to the left (off), there should be no coolant flowing thru the heater core. Verify that the vacuum solenoid valve on the heater core is pulled in (engine running).

When the temp slider is moved away from the LH position, the coolant should flow thru the heater core. The vacuum valve at the heater core is "on".

Moving the temp slider right or left controls the door in the heater to vary the amount of hot air and cool air that mixes in the outlet ducts. Super simple!

The top lever selects where the warm/cool air is to be directed.

Reply
Corvette Stories

The Best of Corvette for Corvette Enthusiasts

story-0

Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

 Joe Kucinski
story-1

150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

 Joe Kucinski
story-2

8 Coolest Corvette Pace Cars (and Replicas) of All Time

 Verdad Gallardo
story-3

Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

 Joe Kucinski
story-4

Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

 Verdad Gallardo
story-5

Top 10 Corvettes Coming to Mecum Indy 2026!

 Brett Foote
story-6

Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

 Michael S. Palmer
story-7

10 Revolutionary 'Corvette Firsts' Most People Don't Know

 Joe Kucinski
story-8

5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

 Michael S. Palmer
story-9

2027 Corvette vs The World: Every C8 vs Its Closest Competitor

 Joe Kucinski
Old Nov 22, 2017 | 10:19 AM
  #9  
Cjunkie's Avatar
Cjunkie
Safety Car
 
Joined: Jun 2006
Posts: 4,008
Likes: 1,487
From: Ashland, OH
Default

Last Feb on my 86 the cable broke on the temp slider. Replaced that along with a new thermostat and the car is a toasty as a new one.
Reply
Old Nov 22, 2017 | 12:25 PM
  #10  
whalepirot's Avatar
whalepirot
Melting Slicks
15 Year Member
 
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
Default

Originally Posted by Hot Rod Roy
vacuum solenoid valve on the heater core
these also fail and may be hard to find.
Reply
Old Nov 23, 2017 | 02:21 AM
  #11  
Hot Rod Roy's Avatar
Hot Rod Roy
Safety Car
15 Year Member
 
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Default

Note to OP: Tom400 (#4) and Cjunke (#9) may be right. Check that first. If the vacuum solenoid on the front of your heater box isn't working, there's a fix for that, too.

Please report back to us.

Reply
Old Nov 24, 2017 | 11:28 AM
  #12  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default

Originally Posted by Hot Rod Roy
Note to OP: Tom400 (#4) and Cjunke (#9) may be right. Check that first. If the vacuum solenoid on the front of your heater box isn't working, there's a fix for that, too.

Please report back to us.

Anyway to check vac solenoid?
Reply
Old Nov 24, 2017 | 02:11 PM
  #13  
belairbrian's Avatar
belairbrian
Melting Slicks
Liked
Loved
Top Answer: 1
Top Answer: 3
 
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
Default

Originally Posted by 71TTop
Anyway to check vac solenoid?
First test would be with car running move temp to cold,

look at the valve position. Then Move temp to hot see if it moves. If it does valve is good.

If it fails disconnect the vacuum line and hook up a vacuum tester to the solenoid pull some vacuum and see if it moves. Car turned off.



You can borrow a vacuum tester at the parts store or pick up one at Harbor freight for around $25 it comes with the brake bleeding kit.

Last edited by belairbrian; Nov 24, 2017 at 02:12 PM.
Reply
Old Nov 24, 2017 | 02:30 PM
  #14  
Hot Rod Roy's Avatar
Hot Rod Roy
Safety Car
15 Year Member
 
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Default

Originally Posted by 71TTop
Anyway to check vac solenoid?
Have you checked the cable connection to the temp control damper under the dashboard on the pass. side? There are several of us trying to help you, but you need to respond to our suggestions.

Originally Posted by Hot Rod Roy
Verify that the vacuum solenoid valve on the heater core is pulled in (engine running).

When the temp slider is moved away from the LH position, the coolant should flow thru the heater core. The vacuum valve at the heater core is "on" (solenoid lever out).
Have you found the heater vacuum solenoid valve? It's located on the front of the heater-a/c housing under the hood.

Reply
Old Nov 24, 2017 | 04:04 PM
  #15  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default

Originally Posted by belairbrian
First test would be with car running move temp to cold,

look at the valve position. Then Move temp to hot see if it moves. If it does valve is good.

If it fails disconnect the vacuum line and hook up a vacuum tester to the solenoid pull some vacuum and see if it moves. Car turned off.



You can borrow a vacuum tester at the parts store or pick up one at Harbor freight for around $25 it comes with the brake bleeding kit.

At lunch I drove to town. On way back I tried the heat in normal position, IT WORKED!

So maybe valve was stuck and freed up, but I will check valve this time by looking to see if it moves.

Thanks.

71TTop
Reply
Old Nov 25, 2017 | 10:44 AM
  #16  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default '84 no heat

Originally Posted by 71TTop
At lunch I drove to town. On way back I tried the heat in normal position, IT WORKED!

So maybe valve was stuck and freed up, but I will check valve this time by looking to see if it moves.

Thanks.

71TTop

Found out yesterday that the lever arm that is screwed into the valve is very rusty. So I lubed it. Then the screw came out due to the rust had eaten away at the mounting hole. So now the lever arm needs to be remounted so it can work.

Another day in paradise.
Reply
Old Nov 27, 2017 | 03:57 PM
  #17  
71TTop's Avatar
71TTop
Thread Starter
Advanced
 
Joined: Apr 2017
Posts: 71
Likes: 5
From: Hendersonville NC
Default '84 no heat

Originally Posted by 71TTop
At lunch I drove to town. On way back I tried the heat in normal position, IT WORKED!

So maybe valve was stuck and freed up, but I will check valve this time by looking to see if it moves.

Thanks.

71TTop

I attached the lever arm to the solenoid and to the valve. Everything works fine. But NOW I see that the valve is leaking where the arm attaches, thus this is what caused the rust to form in first place.

Is there any fix for this or do I have to find a new valve?
Reply

Get notified of new replies

To '84 no heat

Old Nov 27, 2017 | 11:17 PM
  #18  
belairbrian's Avatar
belairbrian
Melting Slicks
Liked
Loved
Top Answer: 1
Top Answer: 3
 
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
Default

early car guys, is this the right part?
https://www.partsgeek.com/gbproducts...ad=47433966132
Reply
Old Nov 28, 2017 | 09:16 AM
  #19  
whalepirot's Avatar
whalepirot
Melting Slicks
15 Year Member
 
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
Default

Not absolutely certain; this is the same, butr check shipping costs:
http://www.rockauto.com/en/catalog/c...ter+valve,6860

Last edited by whalepirot; Nov 28, 2017 at 09:17 AM.
Reply
Old Nov 28, 2017 | 02:27 PM
  #20  
Hot Rod Roy's Avatar
Hot Rod Roy
Safety Car
15 Year Member
 
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Default

Belairbrian and Whalepirot have identified the right part, but there are alternatives for this expensive part. Some have successfully rebuilt their heater valve by carefully extracting the core out of their original valve, and installing the core from p/n 74800. I was planning to do this mod, but when I figured out how the 74800 valve works, I found that I could use the entire valve as-is, to replace my original valve! Here's a link to my procedure. The hoses are even the correct sizes!

https://www.corvetteforum.com/forums...ter-valve.html

Reply




All times are GMT -4. The time now is 01:43 AM.

story-0
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

Slideshow: The 10 most explosive Corvettes ever built based on power-to-weight ratio.

By Joe Kucinski | 2026-05-20 07:23:03


VIEW MORE
story-1
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-2
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE
story-3
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

Slideshow: Ranking the top 10 Corvette engines by torque output.

By Joe Kucinski | 2026-05-05 11:58:09


VIEW MORE
story-4
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

Slideshow: A Corvette pace car nearly matching IndyCar speeds sounds exaggerated, until you look at the numbers.

By Verdad Gallardo | 2026-05-04 20:03:36


VIEW MORE
story-5
Top 10 Corvettes Coming to Mecum Indy 2026!

Among a rather large group of them.

By Brett Foote | 2026-05-04 13:56:44


VIEW MORE
story-6
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

Slideshow: the top 10 things Corvette owners want in the C9 Corvette

By Michael S. Palmer | 2026-04-30 12:41:15


VIEW MORE
story-7
10 Revolutionary 'Corvette Firsts' Most People Don't Know

Slideshow: 10 Important Corvette 'firsts' that every fan should know.

By Joe Kucinski | 2026-04-29 17:02:16


VIEW MORE
story-8
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

Slideshow: Should you buy a 2020-2026 Corvette or wait for 2027?

By Michael S. Palmer | 2026-04-22 10:08:58


VIEW MORE
story-9
2027 Corvette vs The World: Every C8 vs Its Closest Competitor

Slideshow: 2027 Corvette lineup vs the world.

By Joe Kucinski | 2026-04-24 16:12:42


VIEW MORE