yardpro

so ever since i bought my car, the heat has been "sort of on"...
adjusting the temperature settings makes no difference whatsoever. I always get slightly warm air.

The AC works, but it is mixing with the warm air, so it is hard to cool the cab on really hot days.75% from the dash vents, and the rest as defrosters.


I have been waiting to dig into to the diaphragms in hopes that Hans finishes the Carputer. I hoped to do them all at once.

The other night the slider for the vent selection broke off. the **** part broke. The slider is in the far left position, so that keeps the fan off.

So my question is where do i go from here? The lights in the HVAC HEAD UNIT don't work, so i want to fix that as well.

so my options as i see them are (feel free to add options)

1.do nothing and wait.... but i think the carputer is a ways off still...

2. take apart the head unit, beg for a trashed one for parts, and try and replace the arm assembly.

3. super glue

4 install the Volkswagen dash that was just posted...
I really like this idea, but i am not confident about all the soldering for the board, and am not sure about final fitment. I have thought about soliciting for someone to build the board for me....

5. buy a used/refurb. unit for the same price as the Volkswagen....

help me decide....

If i can find someone to help with the volkswagen option, that would be my choice.

MainePorsche

First, the mix of warm air with the AC is probably the heater valve - cheap fix.
Then check the vacuum connections at the base of the center console, but the defective heater valve is what is probably causing the mix.

You can dissect the hvac controller unit, but to find individual parts (ie arm assembly) might be tough.
A rebuilt one would work, but the fiberoptics are never rebuilt. The central bulb will work for the controller face on the rebuilts. You can use prewired LED's and new single filament fiberoptic cables. I'm doing that now for the sliders and fan control illumination - not to bad.

Alan

First - stop dreaming....

You need to get ALL the system components woking normally before you can install anything else and have any idea if its working or not... doing different will be a disaster...

So patch the stock head unit up in the interim...

Likely heat issues are heater valve leaking or non functional - just replace and check vacuum operation.

Bypass flap (comb flap) probably doesn't work - get that fixed

Fix these first - esp check that all the vacuum pods work...

Check the operation of the heater flap motor.

Also ensure you have adequate AC charge and test evap exit temps

Nice if all the flaps work (defrost, footwell and recirculaton) but thats still mainly a distribution rather than termperature issue.

Alan

Aloysius

Where's that basic headunit uprgrade from Hans (no carputer, just the simple hvac upgrade that they were working on)?

robot808

Alan, as usual, is correct. You have to get it working the way it should before you start introducing new ways to screw it up.

Podguy

One thing missed in the discussion is the outside air temp sensor. There is a cooling hose that runs from the alternator and loops up through the front of the fender in front of the left front tire. The hose intersects with a small metal housing with a sensor inside. If this sensor is missing (common) or not working then the temp will never adjust. You will get maximum cooling on one end and max heat on the other. In between there is a mix.

The outside sensor uses a differential between the inside sensor. The inside sensor is inside that funny looking vent on the top of your center console. It is possible the inside sensor does not work, although I have never seen this. There is a small fan that circulates air by the inside sensor. it is possible the fan was disconnected when working on the center console.

Cleaning the the head unit can help as the contacts can get dirty. Get some DeOxIt to clean the contacts. Other than that - testing the flaps especially the center one and checking the heater valve for proper closing is good too.

But I think you will find the greatest gain is sealing up the cabin. A lot of heat comes in from the shifter. As the motor mounts collapse the seal between the torque tube and body leaves a nice gap for exhaust fumes and heat to get into the cabin.

The fire wall can also leak heat. There is a gasket between the engine and the HVAC system. Missing this can leak heat. it is worth checking the firewall for other heat leaks.

If you get your cabin sealed up - I used spray foam - then you will be able to run the A/C on low and be quite comfortable on warm days. Most times I am cycling the A/C off and on because it is too cold even on low.

Alan

I did not mention the temp loop because on max cold slider setting it is bypassed - so it is unlikely to be a contributing factor here. It may still not be working which would affect all other temperatures - so yes certainly worth checking too on the list.

But if the microswitch in the head units works (these are pretty reliable) - then you can still get full cold even with the temp loop disconnected or sensor missing.

Alan

Calgary Ole

Check that the temp mixer motor is working. If it is stuck, it will blend warm air/cool air depending on the cabin temp.

WallyP

Go to our website, then tips and links, then Wally's World, then HVAC. Print it and read it...

Ad0911

Couod it be that the early cars don't have the inside temperature sensor and outside temp sensor? My '78 doesn't have the funny little vent that looks like a coin slot. And one thing that keepspuzzling me is: where can I find the resistor block?

westija

I am working on my AC right now and used Wally's plus Dwayne's write ups, very comprehensive and to the point.
If you start at the brake booster, as they recommend, you might get lucky and have only a leak there (at the 4-way connector) or at the heat valve. The heater valve is cheap and one of the big three has an aftermarket 4-way that is also fairly cheap.
Frpm there, if needed you can start digging into the vacuum actuators. If you have to work on the A/C head , wou will likely have some space to replace the vacuum diaphragm (depending on which one you need). Roger has the diaphragms , so you do not need to replace the entire actuators.
If you need more instructions or pictures, besides what is available, let me know. I have my console and shelves out right now (I am struggling with the door locks and cruise, so might be up for quite a long time with all these parts out.
Good luck

Alan

Some very early cars had mechanical actuators (cables), I think mostly without AC - so this would also have been mechanical mixing flaps. You can pretty easily tell by the slider effort - electronic only slides very easily - smoothly on temp scale and slight detents on distribution. Mechanical will require some effort on both.

Resistor pack is in the air plenum under the hood - near the windshield in between the bulkhead and firewall - under the cowl cover if you have one - central location. Imagine a straight through path from the console vent on the other side. What you will see is a wire connector attached to the back of the resistor pack that is mostly inside the air plenum. Take off the rubber boot from the blower - unbolt it and fish it out (attach a string so its easier to get the new one back in).

Alan

yardpro

sorry it took me so long to follow up on all the advise...

I know that the diaphragms are bad on the flaps, as i have done that troubleshooting already. I have also replaced the alternator cooling hose with a new unit... so the outside sensor is getting flow and is hooked up

I am wondering about the head unit replacement because if i take the center console apart to do the diaphragms, i might as well replace the head then if i am going to go that route.

I checked the heater valve.. it seems to function properly.. I removed it and put the mighty vac on it and it held vac and the valve moved as it should when vac was applied.

I have been meaning to do the diaphragms for a while, but other things have come up...
Water pump/ timing belt...........

driving........

power steering lines.......

driving............

hurricane.........

driving............

etc.....


So i guess since the consensus is that i should just repair the head unit....

Alan

The simple advice is don't change anything to non-stock until you have the stock components working normally.

Any other head unit will depend on all these working correctly... Unless you know that they do - changing anything else will lead you into a debugging nightmare...

Trust me - you really don't want to go there.

Besides the head unit can be swapped out later without removing the console - very easily.
This is the least work in all this, the head unit repairs (just to basic functionality) should be easy too.

Alan

yardpro

thanks..

i have a pm from someone with a parts unit, that i will see if i can get the lever for the temp control and then go from there.