1990 heater
Thread Starter
7th Gear
Joined: Oct 2007
Posts: 7
Likes: 0
1990 heater
Hi Guys on my 1990 there are no codes on panel. Hose going into and out of heater thru firewall is hot. It is automatic climate control. A/c works fine just not heat. Any suggestions? I have done what You all have said by taking fuses out and putting back in but still no heat.
Le Mans Master
Joined: May 1999
Posts: 6,518
Likes: 1,304
From: Windermere FL
I am guessing that you have the temperature adjusted high enough so that it should be putting out heat. Never tried it in the summer myself, hot as heck around here!
Are you positive your heater core was not bypassed? No coolant going thru it at all? Heater core is part #1 and a b1tch to replace and most people bypass them when they go.
There are a couple things that can break. First, the AC control can get dirty and malfunction. But that usually impacts AC too. I think there are threads around here on how to take it apart and service it yourself. My buddy needed that but it screwed up his AC too.
Next thing is to see if the other setting like defroster work. If the vacuum line that drives the system leaks (common problem) I believe it will stay on defrost only.
Next would be to make sure that the door is not obstructed. Really hard to do since it is buried.
I would suggest that if you really want to tackle this yourself, you invest in the GM service manual for your car. Not cheap but worth every penny for problems like this. Don't get the generic manuals. The GM manuals have flow charts on what to check and the diagnostic codes for each problem.
Are you positive your heater core was not bypassed? No coolant going thru it at all? Heater core is part #1 and a b1tch to replace and most people bypass them when they go.
There are a couple things that can break. First, the AC control can get dirty and malfunction. But that usually impacts AC too. I think there are threads around here on how to take it apart and service it yourself. My buddy needed that but it screwed up his AC too.
Next thing is to see if the other setting like defroster work. If the vacuum line that drives the system leaks (common problem) I believe it will stay on defrost only.
Next would be to make sure that the door is not obstructed. Really hard to do since it is buried.
I would suggest that if you really want to tackle this yourself, you invest in the GM service manual for your car. Not cheap but worth every penny for problems like this. Don't get the generic manuals. The GM manuals have flow charts on what to check and the diagnostic codes for each problem.
Thread Starter
7th Gear
Joined: Oct 2007
Posts: 7
Likes: 0
Thanks
I do need to get the book after 2 years. I have alot of others but not that. Defrost works to window but no heat. Heater set sends air to floor but not hot. I took glove box out but could not see very much. The heater hoses are going into the firewall and both are hot. Did not need it in California but going home to Arizona and will need the heat and defrost. Thanks
Racer
Joined: Aug 2005
Posts: 252
Likes: 2
From: lancaster pa
In my 93 i had no heat,first checked to see if the door was working properly,it was.Both my hoses going into core were hot.I flushed out the heater core (backwards flow) and couldn't believe what came out of the core really nasty stuff.After I did that I had good heat 
Intermediate
Joined: Jul 2009
Posts: 30
Likes: 2
From: Pa
Sounds like the blend door is stuck!
I think you need to pull the dash pad to get at the arm
Good idea to check a repair manual
I had my 87' apart twice
Just take your time, take photos and write down what you took apart and where
Good luck
JLM
I think you need to pull the dash pad to get at the arm
Good idea to check a repair manual
I had my 87' apart twice
Just take your time, take photos and write down what you took apart and where
Good luck
JLM
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Simple enough to check the Temperature Door - remove the Resistor Pod (Manual Air) or Blower Module (Electronic) from the left side of the Evaporator Case and look inside. Have someone operate the controls to see if the door moves. If it doesn't, Manual controls it with a cable; Electronic with a motor. If the door moves, the Core is plugged - flush it out as suggested - along with the Radiator and the Block so it doesn't plug up again - and, since it's '90, make sure it isn't leaking exhaust through the head gasket at #7 - that's usually what plugs it up.
Thread Starter
7th Gear
Joined: Oct 2007
Posts: 7
Likes: 0
Thanks Guys
Thanks guys it is the temperature door not working. I did find a gm service manuel on ebay and is on the way. I enjoy reading the posts and trying to fix things myself. I will wait for book to work on door unless You all have some suggestions. Thanks for helping me be a proud corvette owner.
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Thread Starter
7th Gear
Joined: Oct 2007
Posts: 7
Likes: 0
Hey Guys finally got my heater working. I took the fuses out no luck i took the positive battery cable off for 30 minutes no luck. When i was in Arizona decided to replace the drivers side rubber window wiper. Did get my book from ebay and it said to take the neg cable loose so i did while fixing the door. Took a few hours. When i put the battery cable back on the heater started working perfect and been working ever since. Thought i would share this with You
Pro
Joined: May 2006
Posts: 637
Likes: 0
Hey Guys finally got my heater working. I took the fuses out no luck i took the positive battery cable off for 30 minutes no luck. When i was in Arizona decided to replace the drivers side rubber window wiper. Did get my book from ebay and it said to take the neg cable loose so i did while fixing the door. Took a few hours. When i put the battery cable back on the heater started working perfect and been working ever since. Thought i would share this with You
Press fan up and down buttons until it shows -00.
Press aut fan speed button once and it will show any codes, since you dis- and reconnected neg. batt. cable, you cleared the codes and probably it will show 00.
When you get the manual, you can read all about it in the AC section somewhere in the beginning of the main manual.
You will be surprised what a magic thing this automatic AC controller is.
