Help! 1995 Heater problems, body wobble

[Nucman]

I have 2 questions, my vette has the electronic AC/Heat controls. My A/C works great but my heater blows semi warm air, never hot air. I have run a flush thru the heater core with a garden hose and get a very good flow. My engine temp runs around 210 degrees. I did notice that the light above the heater button sometime flashes and then stays on steady. I read that the controls need to be reset, I have pulled fuses to reset it and also disconnected the battery to reset it. Nothing seems to work. I had a overheating problem for a long time so the thermostat, radiator have both been replaced.

My second question is when I remove the top off my car and drive it, the body and front end seems to wobble alot.

Anyone had either of these problems ? any help would be appresiated.

Thanks

 

[boomdriver]

I have 2 questions, my vette has the electronic AC/Heat controls. My A/C works great but my heater blows semi warm air, never hot air. I have run a flush thru the heater core with a garden hose and get a very good flow. My engine temp runs around 210 degrees. I did notice that the light above the heater button sometime flashes and then stays on steady. I read that the controls need to be reset, I have pulled fuses to reset it and also disconnected the battery to reset it. Nothing seems to work. I had a overheating problem for a long time so the thermostat, radiator have both been replaced.

My second question is when I remove the top off my car and drive it, the body and front end seems to wobble alot.

Anyone had either of these problems ? any help would be appresiated.

Thanks

because the top is a frame section, the car will act like its got a broken frame with the top off. Normal for a C-4.

Heater, is all about the flow to the core and the air mix inside. If there have been any changes to the water system under the hood, the flow to the heater may have been reduced.

If there IS good flow of heated water to the core, it has to be mixed inside. That is the job of the elec control and the control head tells the mix door how much and when. If you set the heater to 90 that over-rides the sensors and goes to full hot. If its still not getting good warm air then the problem may be elsewhere. Check vac line to the cabin behind the distributer.
Also look at the heater water control valve under the hood. That is supposed to close when a/c is in use and bypass the hot water. When the heater is turned on the water control should open to allow circulation thru the heater core. This is also vac operated and does stick. Have someone operate the heater controls and with the engine running observe the action of the valve. 210 on the gauge is more than enough to cook the interior.

 

[Nucman]

Thanks for the info

Thanks, I removed the battery cable again today and let it sit awhile. The heater got a little warmer but still not hot. is there a heater control valve under the hood, I thought that was only on the older C4s. I dont see one on m 95 under the hood.

 

[boomdriver]

Thanks, I removed the battery cable again today and let it sit awhile. The heater got a little warmer but still not hot. is there a heater control valve under the hood, I thought that was only on the older C4s. I dont see one on m 95 under the hood.

You;re right....they stopped using the heater control valve before yours.It was a worthless POS...a good idea in theory but junk in reality.
I failed to notice your yr model.

There is a set of button codes and displays for the electronic a/c that can show a diagnosis or trouble codes much like the engine computer. I have that process saved somewhere and will post it if I can find it. Your yr has an electric mix door motor and other people here have had trouble and had to replace them. Hopefully the code display will indicate what the problem is.

 

[vetteoz]

My A/C works great but my heater blows semi warm air, never hot air. I have run a flush thru the heater core with a garden hose and get a very good flow. My engine temp runs around 210 degrees..Anyone had either of these problems ?

Not the only one

See
http://www.corvetteactioncenter.com/forums/c4-technical-performance/124768-no-heat.html
http://www.corvetteactioncenter.com/kb/questions/85/1990+-+1996:+HVAC+Diagnostic+Codes

 

[vetteoz]

There is a set of button codes and displays for the electronic a/c that can show a diagnosis or trouble codes much like the engine computer.

Corvette Action Center Knowledgebase :: 1990 - 1996: HVAC Diagnostic Codes

Check vac line to the cabin behind the distributer.

Vac only controls vent position.
Temp control is by blend door as you state

 

[Nucman]

Heater problems

Thanks guy for yor replys, I had to drive the car 200 miles yesterday and it was cold as hell. I finally stopped and got some duct tape and put over the vents near the windshield, it cut down on the air volume but at least the air felt a little warmer. I did do the HVAC diagnostics this morning and got a 01 code for system faults (temp door motor circuit fault) and when reading the temp door travel range I got a 120, temp door position requested I got 00= full hot. So I am not sure if it is the controls or the door letting in cold air from the outside. Getting deserate now 29 degrees outside today.

Thanks so much for you help !!

 

[Nucman]

95 heater problems

Another important thing also, when I turn down the controls to 60 degrees the air gets cold, when I turn it back to 90 degrees it gets luke warm, but never hot, maybe this will give you another clue what maybe wrong.

thanks,
Nucman

 

[Schrade]

29? Yikes. Brrr. Just think how cold it would be if Gore didn't invent global warming!!!

Time to start wrenchin' (or unscrewing)... Have you found anything behind the dash? Keep dash screws sorted out. One SURE way is putting each screw back in its place when the part is out of the way.

Kind of tedious, but none will get lost that way, and you get more 'familiar' with it...

 

[vetteoz]

I finally stopped and got some duct tape and put over the vents near the windshield, it cut down on the air volume

Could you not put the system on recirculate so it gets no outside air?
There is a seperate vac operated door that controls air in from outside

 

[vetteoz]

when I turn down the controls to 60 degrees the air gets cold, when I turn it back to 90 degrees it gets luke warm, but never hot, maybe this will give you another clue what maybe wrong.

Obviously the blend door is moving to allow SOME air flow over the heater core but not ALL air as it should on max temp
When on full hot the door is located such that all air must pass through the heater core.
When on a in between temp ,the door is positioned to mix ( blend ) hot and cold air to achieve your desired temp setting

 

[Nucman]

1995 Heater problems

I agree Vetteoz, I am pretty sure the blend door is not opening or closing completely letting cool air to mix with the warm air. In the diagnostics when performing the "temp door position requested" the result is 00 = full hot. So I would assume the control is telling the door to move to the hot position. Thanks for your input ? Anyone had to replace the Temp door, anything I should know? I assume it is located under the passenger side dash.

Nucman

 

[Schrade]

Someone once did a thread on temperature door work, with pics, for C4. You're gonna' have to put on your search hat; it's been a year or 2 since I saw it, and I don't remember if it was CAC, or DC, or C4guru (start there), or CF (check LAST ).

I have dozens of dash dis-assembly pics ('94), but I think you don't go that way for duct work...

 

[Nucman]

1995 Heater problem FIXED !!!!

I want to thank Boomdriver, VetteOz and Schrade for all your wonderful advice and taking the time to look up the diagnostics for me. I removed the sensor in the top of the heater box under the hood and could see the air mix door half way closed (with the heat set at 90 degrees) I simply pushed the door closed with a screw driver, went inside the car and it was blowing hot air !!!! I then set the heat at 60 and checked the door and it was half open, i reset the heat to 90 and checked and the door had closed completely. So it looks like the door was just sticking. Seems to work fine now. You guys are the BEST!!!!!

Just one more question, just the other day I was sitting at a light and the car started idling rough then the service engine light came on and the idle smoothed back out. This happens everytime I drive it now. I attempted to read the codes with the correct reader and the reader says it cannot connect. I understand there is a way to short the socket to read codes with the service light. The book I have (95 corvette Haynes manual) shows the wrong communication link connector the A and B terminals are differnt on my car.

Thanks,
Nucman

 

[vetteoz]

I assume it is located under the passenger side dash.

Pic in the " no heat " link I posted for you above ;squint:

http://www.corvetteactioncenter.com/forums/c4-technical-performance/124768-no-heat.html#post1052367

 

[boomdriver]

I want to thank Boomdriver, VetteOz and Schrade for all your wonderful advice and taking the time to look up the diagnostics for me. I removed the sensor in the top of the heater box under the hood and could see the air mix door half way closed (with the heat set at 90 degrees) I simply pushed the door closed with a screw driver, went inside the car and it was blowing hot air !!!! I then set the heat at 60 and checked the door and it was half open, i reset the heat to 90 and checked and the door had closed completely. So it looks like the door was just sticking. Seems to work fine now. You guys are the BEST!!!!!

Just one more question, just the other day I was sitting at a light and the car started idling rough then the service engine light came on and the idle smoothed back out. This happens everytime I drive it now. I attempted to read the codes with the correct reader and the reader says it cannot connect. I understand there is a way to short the socket to read codes with the service light. The book I have (95 corvette Haynes manual) shows the wrong communication link connector the A and B terminals are differnt on my car.

Thanks,
Nucman

Glad you got it.. Yes, these things are good for sticking. armour-all attracts dust, oil grime, moisture, all cause the vent doors to stick.
If it happens again you;ll know what to do..

The engine...yeah, get the codes. something is happening at idle thats sending the ECM back into the back-up mode or open loop because there is a bad signal input from a sensor. When that SES lite comes on that the sign that it went back to open loop. Might wanna look for a vac leak or TPS or IAC leak. The codes will confirm something.
Good Luck

 

[Schrade]

Paper clip in #4 and #12. It will light up the LED dash with MULTIPLE modules, and codes, H - history, and C - current. Have a pencil at hand.

No paperclip? You can use the fallback analog jumper, but it's hard to count pulses while you're screaming :W

 

[Hib Halverson]

First, use the Haynes manual for a cat box liner. The Haynes manual for C4 lacks deatail and contains many errors. Worse yet, it's section on engine controls diagnostics is so short and full of errors it's useless. If you going to do engine controls diagnostics or other electrical troubleshooting there's no avoiding the purchase of the factory service manual.

You can't use a "code reader" to read DTCs from a 95 ECM. You either have to use CCM diagnostics to get the ECM's 2-digit codes (discussed at length in the FSM and in brief in the above post by "Scharade") or a scan tester. You also cannot use flash code diagnostics (where you short the diagnostic pin to ground, key-up and count the MIL flashes) on a 95. The last model year for LT1 and flash code diagnostics was 1993 and maybe a very few, early-production 94s.

 

[vetteoz]

Paper clip in #4 and #12. It will light up the LED dash with MULTIPLE modules,

Bottom of page
C4 Corvette Diagnostic Code Recovery Techniques

 

[Schrade]

Yeah - that's where I got the pinout pic.

I wasn't going to say anything - I think some know all they're going to know (or want to know)...

Forum nazis. :eyerole I hate forum nazis.

Heil HIBler!!!