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Discussion Starter #1
1983 p-type

I've been reading and searching. I've done the following:

Replaced Water Valve
Checked for leaks
Burped the radiator
Made sure the fluid is full
I get heat to the core, both hose's heat up.
I checked all fuses...all good

I did the first part of the Functional Test

from the trouble shooting TSRM Guide for the heater

INCORRECT TEMPERATURE OUTPUT:

Control Cable broken or binding
--since the power servo wont work I can't check this....afaik

Heater hoses leaking or clogged,
-they all seem good. I've not taken them all apart nor flushed them with water. No leaks, I've checked for that.

Water Valve faulty, -replaced with new unit from toyota

Air Dampers Broken,
-unknown

Air Ducts Clogged,
-since I have no heat whatsoever seems unlikey...I just replaced the blower and checked those ducts I could see and blew out with air what I could.

Heater Radiator leaking or clogged,
-new radiator. Flush system when installed

Heater control unit faulty,
-yeah....most likely but what part?



I connected to the check connector of the amplifier, I put the temp control lever to 77. I had clicking and movement of the power servo stem. THE TSRM says this is a vacumm leak

I have not.....

checked the vacuum circuit for leaks...excect for a quick cursory look and listen.

From my reading here that clicking seems to fall into this..

This is a common problem with Mk2's. The noise is from the relays that control the heater valve actuator (the gold thing behind the radio). The slide resistors in the heater controls can wear out, and have bad internal connections with the sliding arms (levers). Basically, one second they would send a voltage signal to the actuator circuits, turning on a relay, and the next, the internal connection would break, the voltage signal would go away, and the relay would click back off. The signal can change very rapidly due to road vibration, or whatever, and that change between on and off can wreak havoc on the relay systems back there. The noise can be really annoying, especially if you are cold and the heater just wants to make noise, and not heat!
As soon as I replaced all those switches the noises pretty much stopped, and the heater works just fine. Major PITA job, but worth it.
All this crap could have been avoided if Toyota had just given our cars cable controlled manual heater valves like every other car, but then we couldn’t have had "Automatic Air Conditioning". But luckily, the Supra is *not* like every other car, and I love it!

Vern
So I wonder if I should look at the heater control itself before I search for vacuum leaks.

I've got a spare heater level, it was from an unknown donor car. Should I do a clean up and try the spare or try and see if there is a new part still available?

Jim King also had this to say.....

The fan in the console draws in air to read the cabin temperature.
There is a thermistor just in front of it.
Along with it, the outside temperature sensor, the solar sensor and a few other water temp sensors and relays provides the data. Note the test connector bypasses all of this.
With this data, the temp lever selection, the AC amplifier 'tries' to keep the cabin temperature at a consistent level.
If fact, having this thermistor at the back of the console is a very good idea, as most are located in the dash, which doesn't give that accurate of a read.
The mystery is why the AC amplifier continues to send a small voltage to DVV, located left and behind the radio. It's a vacuum valve driven by magnetic relays. The relays are generating the clicking.
I tried a new factory amplifier and it still clicked.
Based on the circuit, a *very* small vacuum leak would cause the servo to slid right, sending a new resistance value to the amplifier. So, if either the servo or DVV was leaking, this could be a cause.
However, if it were a consistent vacuum leak, it would do this *all* the time.
One test I would like to see is with a MK2 that clicks, and try pulling vacuum against the servo. Increased by small amounts, because it could be possible the rubber diaphragm is leaking at a certain point. Same could be with the DVV.
I do know they switched to electric servo motors in later Toyotas.
Vern does not say that he bought new switches but I'm going to assume that is what he did. I'm also guessing that the temperture lever is the only one that needs to be replaced as it is the only one that sends a signal to the power servo.

Its all bit confusing but that clicking Vern speaks of is exactly what I get. I can see the power servo not being able to move correctly in time with those clicks. Any input or help would help.

Should I try to replace that heater temp lever with new and go from there? I really don't know which relay Vern was replacing. I am very unsure of what to replace or check for the relays...
 

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I believe in other threads people have mentioned it was the DVV (Dual Vacume Valve) that was the source of that very annoying clicking.
 

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Sheesh....I've done search after search. Then the correct thread shows up. Anyway I'll post this reprint of it.

I wish they would sticky this one.
http://forums.celicasupra.com/showthread.php?t=1308&highlight=heater+clicking

Here are the post I thought most helpful. I will try out this fix and see. I've got my dash apart and getting the cleaner and pulling out the DVV should be fairly striaght forward.

06-18-2003, 09:56 PM
The "tick-tick" that you're hearing is coming from the DVV (Dual Vacuum Valve). See if this makes any sense and I'll try not to write a short book in the process:
The DVV controls the position of the power servo stem by applying and bleeding off vacuum from the power servo diaphragm.
The setting of the temp. control lever establishes the baseline position of the blend door on the interior air box outlet which is mechanically connected to the power servo stem. The DVV is switched On, applying vacuum to the power servo diaphragm, and then switched Off once the correct position of the blend door is established. The problem occurs when a vacuum leak allows vacuum to be bled off of the power servo diaphragm.
The vacuum leak allows the power servo stem to move slowly to the left after the DVV is switched Off, which in turn causes the A/C amp to turn on the DVV once again in an attempt to re-establish the proper position of the power servo stem, which it does, but only temporarily due to the vacuum leak.
The DVV controls the position of the power servo stem by applying and bleeding off vacuum from the power servo diaphragm. The setting of the temp. control lever establishes the baseline position of the blend door on the interior air box outlet which is mechanically connected to the power servo stem. The DVV is switched On, applying vacuum to the power servo diaphragm, and then switched Off once the correct position of the blend door is established. The problem occurs when a vacuum leak allows vacuum to be bled off of the power servo diaphragm. The vacuum leak allows the power servo stem to move slowly to the left after the DVV is switched Off, which in turn causes the A/C amp to turn on the DVV once again in an attempt to re-establish the proper position of the power servo stem, which it does, but only temporarily due to the vacuum leak.
The DVV contains two very small vacuum valves that are operated by two very small solenoids, all internal to the DVV. One valve is used to control the supply of vacuum to the power servo diaphragm while the other controls the amount of vacuum bleed off from the power servo diaphragm. Am I making any sense yet? :lol:
Check for any vacuum leaks in the DVV/power servo section of the auto A/C system. You may have a leaky vacuum hose, a leaky power servo diaphragm, or a leaky bleed valve in the DVV (which is what I've found in the past). Try swapping out the DVV and see if that cures the cycling problem.
I've seen one case where the DVV bleed valve was to blame. The valves are a needle and seat type arrangement that resemble a scaled down version of the needle and seat in the float bowl of a carburetor (only the needle tip is hard plastic instead of butyl rubber or Neoprene in the DVV). :? Repairing the crummy valve needles and seats in the DVV has proven to be a less than enjoyable experience for me, and I highly recommend replacement of the DVV with a new one instead! IOW, don't attempt to disassemble the DVV unless you have steady hands, nerves of steel, and much patience to deal with the several tiny springs and steel check balls that lurk inside. Chuck the DVV and buy a new one!

The reason the "tick-tick" stopped cycling and ended with a single tick is because your engine wasn't running and thus no continual vacuum supply to the DVV. The more erratic ticking sound that you're hearing when you move the temp. lever to the far right is due to poor contact in the temp. lever potentiometer. Giving the potentiometer a shot of contact cleaner should improve or even cure that problem. The contacts tarnish over time and make poor contact which drives the A/C amp and the DVV crazy.

Thanks for the nice words of wisdom, Marblehead! $375.00 for a new DVV?? The parts dept. must've looked up the wrong part or else they're trying to rip you off big time. :!: I checked today and new DVV's are still available. The part number is 88690-14530. Price is $64.27 list and my cost is $48.20 each. If anyone needs a new DVV and can't find one for this price or cheaper, let me know by e-mail and I'll order one for you. These things may become extinct in the near future so I'm going to have one ordered for myself just in case. You just never know when certain parts will suddenly become obsolete and discontinued for the MKII.
Find a local electronic parts supply place and buy a spray can of GC brand "De-Ox-It". That stuff works great and has a lubricant to help keep the contacts from wearing. Just remember to grab a can that has the red plastic tube taped to it.

Dave A.
This is what I'll try first...seems like a great way to go.

08-26-2007, 08:11 PM
frobozz

Having just gone through all this today, I'll add my 2 cents.

The potentiometer (temp control) looks like a standard off the shelf slide pot, 3K ohm... except I could not match its rating and physical dimensions through any supplier I checked. So if you want a new one, looks like Toyota is the place, as long as they still carry them. That's a mother to get at, including the tie wrap you need to cut to get the wire free! I took mine apart, cleaned it up, adjusted the pair of contacts that run on the resistive strip to land in a slight different spot, tensioned the contacts and the pressure legs a little more, and reassembled it. Works great now! Before, measuring while moving it, it was all over the map. Now it's rock stable. It looks like all the grease they put all over the plastic lever pivot points back there eventually migrates into the pot, so that's what needs to be cleaned up. The tuner cleaner approach might actually work, without so much disassembly, but I wanted to do it right.

Now to the DVV... Taking that apart isn't so bad. On the top (plastic, vacuum side) and bottom (metal, bleed side) there are 4 tangs to bend back to get the end plate off. Once you do, you will find a plunger with tapered rubber tip (like a carb float valve) and a spring, and a rubber seal. On the top you will see the needle tip and below it is the spring. On the bottom you will see the spring and above it is the shuttle, with rubber tip pointing up. On the top, the other rubber seal is a square-edge o-ring and on the bottom the seal is a flat rubber disc, with nubs that go up inside the spring, presumably to help keep it centered.

No check balls or anything so easily lost.

I rejuvenated my valve with two old tricks. I used a heat gun on low to pull the dent out of the rubber tips. And I stretched the springs about 1/4 again their length (stretch until they're that long at rest when you let go) to put more pressure on the tip seals. The solenoids pull the valves open, and then the spring is what provides the pressure to keep each valve closed. Now it works perfectly - no more infernal clicking!

I found a really easy way to tell if it's your bleed valve that's the problem (and it looks like that's usually going to be the case.) Reach up under the dash and on the bottom of the valve, where there is a round disc with holes in it (the bleed vent)... put your thumb over it. If the clicking stops, then it is definitely the bleed side of your DVV leaking. (You have to pull off that one tiny section of vent extension under there to even get at it to do this, but you don't need to unscrew the DVV itself, unless you need to remove it to replace or repair it.)

Hope that helps someone!

Duncan
I'll try and get some pictures of all this while I'm at it. I do have a 'spare' temp control from the PO.

My undying thanks to Dave A , Duncan and 84SupraMD, you got me try one more search and I feel like I hit the jackpot.
 

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Update on the DDV part in the US. I spoke to the dealership this morning. 3 left in the US selling for 69.11 part number 88690-14530

Since I did not want to chance rebuilding mine and have it still not work I ordered one. Now there are two left.
 
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