another heater issue - I searched I promise!

[riffman12]

Apologies for making another one of these threads. I've looked through all the heater issue threads I could get my hands on.

Here's my situation:

Recently purchased my '97. $153k on the clock. The front heater is not blowing hot air, but the rear heater works pretty well. The A/C also blows ice cold which is good. When the car is warmed up, the temp needle sits right smack in the middle of red and blue.

Here's things I have tried so far:

1) Checked the heater valve at the firewall. When I switch the slider to hot, the cable is not even moving the valve. So I unhooked the cable and moved the valve manually and it didn't really change anything.

2) The PO told me that the heater core was flushed recently trying to fix the issue


Here's what's strange. If the engine is at operating temp and I've been driving around for a while on cold. If I switch it to hot the air is REALLY nice and warm for about 20 seconds then goes back to lukewarm/cold.

Also, it seems that when the slider is pushed to hot, the air flow is reduced significantly.

Given these points, where should I look next? I figured I might take a look at the servo behind the radio and see why the cable isn't moving at the valve, but I'm not sure if that's the whole issue.

Any help would be greatly appreciated. I want to take this baby up to Tahoe but it's going to be pretty chilly with no heat!

 

[izzyandsue]

I would guess the core was not flushed enough or properly. The cable not moving the valve has a lot of posts with pics on how to fix, but heater cores do not. Here is mine:

Heater Core Flushing - OWNED!

 

[riffman12]

I would guess the core was not flushed enough or properly. The cable not moving the valve has a lot of posts with pics on how to fix, but heater cores do not. Here is mine:

Heater Core Flushing - OWNED!

Awesome thanks I'll take a look at that.

New development: i had my gf move the heater switch while I watched the valve and it is moving now.

However, the valve leaked a bit of fluid and i can see a fair amount dried under it.

Is there a chance the valve is gummed up and just needs cleaning/replacing?

But then why would it get hot for 20 seconds then back to cold?

Gah a mystery!

 

[ajax1]

Change that valve or have another ready before you mess with the hoses it is probably ready to crack as soon as you torque on it

 

[BILT4ME]

Awesome thanks I'll take a look at that.

New development: i had my gf move the heater switch while I watched the valve and it is moving now.

However, the valve leaked a bit of fluid and i can see a fair amount dried under it.

Is there a chance the valve is gummed up and just needs cleaning/replacing?

But then why would it get hot for 20 seconds then back to cold?

Gah a mystery!

It's not uncommon for those heater valves to get brittle and suddenly decide to fail as in break off one of the hose ports. Order one from RockAuto (most folks on here say they're OK even with not getting the OEM one. One of the VERY few things that seem to be OK NOT being OEM)

It's possible that the internals are not moving like they should. Easy to replace, just need to make sure you bleed the air back out of the system and use the CORRECT color of antifreeze (that would be whatever color is already in there. If it's brown, FLUSH it and use green.)

Both of these are part of "baselining"

Good Luck!

And Welcome to 'MUD!

 

[coastie720]

Well, the temp slider controls the servo behind the radio which in turn controls the heater valve cable. I had the same issue with the heat valve not moving with the temp slider. It was intermittent, then one day it quit working altogether. My problem was with the controller. There were two bad traces on the board from the slider to the blue connector on the back. I jumpered around them and now it's fully functional.

Moving the heater valve manually will do nothing as the servo behind the radio controls a baffle that allows air to flow over the heater core when in the heat settings. If that baffle is not "open" you will get lukewarm heat.

 

[riffman12]

Well, the temp slider controls the servo behind the radio which in turn controls the heater valve cable. I had the same issue with the heat valve not moving with the temp slider. It was intermittent, then one day it quit working altogether. My problem was with the controller. There were two bad traces on the board from the slider to the blue connector on the back. I jumpered around them and now it's fully functional.

Moving the heater valve manually will do nothing as the servo behind the radio controls a baffle that allows air to flow over the heater core when in the heat settings. If that baffle is not "open" you will get lukewarm heat.

I think this sounds pretty close to what I have going on. Perhaps a combination of a servo that's on its last leg and a heater valve that is gummed up / leaking.

Do you have any more info / pics on what you did to the servo? Was it a big job? Is there a writeup anywhere?

 

[coastie720]

I didn't touch the servo. My problem was with the controller in the dash. I don't have any pics, but are you good with a multimeter? I can walk you though some checks on it.

Gain access to the back of the controller. There will be a white and a blue plug that plug into it. Remove the blue connector. Now, you'll need to take resistance checks on pins 1, 2, & 3. Check resistance between 1 & 2. Not sure the value, but you should get a stable number. Thats the measurement of the entire temp slide resistor. If it's "OL," then you're going to have to open it up and $1 says you have broken traces like I did. If not, then measure between 2 & 3. This value should change as you move the temp slider back and forth. It's a three hand job BTW .

My guess is that these will all be open. If that's the case, open it up and physically trace the runs on the board from those blue connector pins to their origin on the slider and solder a jumper wire between that point and the connector pin solder joint. OR buy a new controller...

Good luck. I also attached the AC section from the FSM that's really helpful in troubleshooting...

 

[riffman12]

I didn't touch the servo. My problem was with the controller in the dash. I don't have any pics, but are you good with a multimeter? I can walk you though some checks on it.

Gain access to the back of the controller. There will be a white and a blue plug that plug into it. Remove the blue connector. Now, you'll need to take resistance checks on pins 1, 2, & 3. Check resistance between 1 & 2. Not sure the value, but you should get a stable number. Thats the measurement of the entire temp slide resistor. If it's "OL," then you're going to have to open it up and $1 says you have broken traces like I did. If not, then measure between 2 & 3. This value should change as you move the temp slider back and forth. It's a three hand job BTW .

My guess is that these will all be open. If that's the case, open it up and physically trace the runs on the board from those blue connector pins to their origin on the slider and solder a jumper wire between that point and the connector pin solder joint. OR buy a new controller...

Good luck. I also attached the AC section from the FSM that's really helpful in troubleshooting...

Thanks a lot for writing that out bud. Depending what my mechanic says tomorrow, I might be PMing you for some more questions around this!

 

[riffman12]

ok quick update:

Changed the heater valve as it was leaking and pretty gross looking. Unfortunately it didn't fix my problem.

This weekend I'll be pulling apart the dash to access the controller and solenoid to see if there are any obvious electrical issues there. I'm not great with electronics so I'll be cleaning and checking solders to the best of my ability (with the tips from coastie)

after that I guess all there is left to do is reverse flush the core and hope i don't break a piece of corrosion stopping it from leaking all over my floor

 

[riffman12]

Update for anyone who's interested:

I checked the servo in the dash and it's working correctly so I took Izzy's advice and flushed the core with CLR. Getting almost 130 degrees now.

Thanks everyone for thr advice

 

[slow95z]

i need to clean mine out also with CLR. it gets warm but it takes a while. glad to see you got it all fixed.

 

[izzyandsue]

Update for anyone who's interested:

I checked the servo in the dash and it's working correctly so I took Izzy's advice and flushed the core with CLR. Getting almost 130 degrees now.

Thanks everyone for thr advice

Glad it worked out! You may have to burp the system a couple of times to get all the air out, it should get hotter than 130, not that 130 is bad!

 

[riffman12]

Glad it worked out! You may have to burp the system a couple of times to get all the air out, it should get hotter than 130, not that 130 is bad!

Yeah it's been a bit erratic since. What's the best method to burp it?

 

[izzyandsue]

I use the Amazon burp funnel, run the engine nice and warm for a good 20 and just follow the instructions for it, easy to do.

Amazon.com: Lisle 24680 Spill-Free Funnel: Automotive

 

[riffman12]

I use the Amazon burp funnel, run the engine nice and warm for a good 20 and just follow the instructions for it, easy to do.

Amazon.com: Lisle 24680 Spill-Free Funnel: Automotive

cool thanks. Just ordered

I hope this fixes my issues. Getting pretty weak heat again at times. And some gurgling noises behind the dash when accelerating hard with the heater on

 

[izzyandsue]

Right, the gurgling is the air pockets, entrapped in the system. Burping it should take care of it. The funnel ensures bubbles have a way out on the highest point. Some people will do it without a funnel by parking on a steep incline too, radiator up, I have not tried that.

 

[riffman12]

Right, the gurgling is the air pockets, entrapped in the system. Burping it should take care of it. The funnel ensures bubbles have a way out on the highest point. Some people will do it without a funnel by parking on a steep incline too, radiator up, I have not tried that.

Ok now I'm totally confused. I flushed the core and bled the system with that funnel. I had really hot heat consistently for about a week.

Then last night I drove up to the mountains to go snowboarding. Wasn't terribly cold most of the way up so i had it at low heat pointed at feet and windshield.

Then at the summit I wanted more heat and it just won't get hot. Just sort of room temperature.

Why would it suddenly go back to it's old habits after being great for a week??

Any suggestions on what to do next?

 

[riffman12]

Anyone got any ideas? Do I just need to flush again?

I'm freezing my nuts up here!

 

[izzyandsue]

Not much I can think you can do there. My guess is maybe your cooling system needs flushing, might have redeposited mud into the heater core. Just a guess