Only 1 temp setting: HOT!!!

[GoM100Go]

The mirror gloss on my car may be illegal, in some solar systems, Put on my new clear front lenses and LED's, love my new sunvisors fresh from the UK -lookin great! Next project: no matter what I set the temp dial to. I only get one temp: Hot. So I felt behind the panel and I think the rod that controls the heater flap is stuck on heat. Any advise or previous experiences. No idea where to begin... I am Looking through the shop manual to see how it all goes together. Thanks for any advise.

- James

[hatters]

There is a thread on here somewhere all about the heater knob control rods and how to fix them, I cant remember where it is and when It was posted but if you have a look through all the heater postings no doubt you will find it eventually

[HJ2]

I would start looking under the hood first (the other end of the control rod), the dreadded heatervalve against the firewall.
Easy and cheap to replace. Use an all plastic one to prevent it from corroding again (no Brass part as per original)

Good luck
Henk-Jan

[Brit-Car-Nut]

Temperature and air flow are different issues.

If you have proper flow from the windscreen vents, the facia vents or the footwell vents, then the control rods are probably fine.

If you just have a constant hot output, then the heater valve or the vacuum lines are suspect. If the vacuum control circuit fails either by a bad controller or vacuum leak/blockage, the system fails in full heat mode. Better to be HOT than freezing.

Check for a pinched, blocked or broken vacuum feed to the heater valve.

[GoM100Go]

Ok, thanks for the leads. I will look into the valve first. Since I do have air flow, only in the 3-4 position, but there is flow.

-James

[Lotus54]

Does the heater valve open with vacuum, or close with vacuum?

I got a replacement valve (from the Wiki) but wanted to know if it was the correct way or not.

Anyone know for certain?

AC Federal car (if it matters)

Mark

[Brit-Car-Nut]

From what I remember reading, it closes with vacuum, but I hope someone else jumps in to confirm. I remember reading posts that were complaining that on a hard run (lower vacuum), the air coming from the vents went up significantly.

[GoM100Go]

Update: New Valve installed and still HOT a bunch of HOT air. In any setting. Good thing the temp valve set me back only 70 bucks installed. Now i am back to thinking its a disconnected rod... I turn to it to cold and there is no change in the temp. I wonder what makes the valve on it move? What is the suction from turning the dial supposed to come from. Because when I turned the temp knob to hot or cold it states open. I did check the lines for pinches or blockage.

-James

[epipete]

I'm reading this and becoming ever more confused as I understand it the direction of air flow is vacuum controlled whereas the temp is mechanically activated.

Turning the temp control pushes/pulls a rod which is connected to a flap on the heater, the temp is determined by a flap allowing airflow over the heater core, it reduces flow when you set to cold and increases it when set to hot!

Assuming this to be correct, then you need to find out if the lever is connected - a nightmare!!! Firstly, when you turn the temp control can you feel any resistance ie do you get a sense of 'attachment'? Can you hear anything you should be able to hear the flap closing.

If you are in the US I assume its just the drivers controls that are switched to the left in which case you may be able to reach the rod at the control via the glove box. Check here first if you can feel the rod which runs forward from the control along the transmission tunnel, you will get an idea if and from wher it is disconnected.

Take a look in the manuals first - its all there.

Pete

[Brit-Car-Nut]

Here is the section from the service manual

heaterfunction.pdf

The water valve is controlled by a vacuum switch at the heater matrix which turns on the heat when in heat mode.

I left out the sections regarding A/C, thus the jump in pages.

[epipete]

So, if I read correctly; set the heater to cold (assuming its all correct) run the engine, the heater matrix should remain cold because the microswitch is off, turn the heater up allows water in to the matrix and then into the car according on the distribution position. The temp is regulated by the lever controlled flap.

Viz a viz the problem is either the control rod or the microswitch!

Or am I completely off beam?

[Brit-Car-Nut]

Sounds to be spot on. Could be linkage or a bad vacuum micro-switch.

[GoM100Go]

As I turn the knob it does give some resistance but no sound as if a flap is moving. I can feel the rod from behind, lowering the glovebox. Thank your the link its the same i was using to see what its supposed to bie conencted to. I will try to reconnect it... The 1.2.3. It gives for reconnecting seems so simple - as if you had the dash the dashboard completely removed... Well that's going to be my next step. Then I guess the last thing it would be is the micro switch. Thanks for the input guys.

-James

[Lotus54]

I'd make sure the vacuum is working first. Easy to do.

Remove the hose from the valve, start the engine, turn the control to cold. See if you can feel vacuum on the hose.
If not, then I'd work backward. OR apply vacuum to the valve and verify that the heater stops putting out heat.

I haven't been in further, but just chckd mine so know that is the way it works, vacuum to turn off the water valve.

Mark

[epipete]

Ok, a sleepless night worrying about all things M100 has left me thinking 'yes' by all means check this vacuum but it won't matter because all it's doing is allowing (or stopping) hot water to the matrix and we know that water is going there anyway, what isn't happening is that the flow of air is not being directed around the matrix but is continuing to be sent through it hence the hot cabin & hence it must be associated with the rod.

[HJ2]

Ah! Deduction dear Watson

[GoM100Go]

Sounds like I have direction! Thank you so much, rained all day today... So next weekend I will tackle the ROD. Thanks again for all help. I will keep updating.

[Doug]

James,

Sounds like the cold-hot dial pushrod to me since your first post. Now I remember from this that you can reach this rod with your skinny left arm reaching behind the center dash from over and around the accel pedal area in the driver's footwell. I distinctly remember connecting-disconnecting this rod. It's seen on page 21 of the .pdf that John graciously posted above (on page 12 of 17). If disconnected you have to maneuver the rod end into the hole and then flip around and "clip" that rod holding clip seen in the pic.

True you should feel the rod resistance normally when moving the C-H dial. If only you had another Elan nearby you could see the difference with one working. Let us know how it goes playing with your rod.

-D

[tigerdog]

JIf only you had another Elan nearby you could see the diffnce with one working. L

Smaug is available for comparison. Feel free to get in touch.

[GoM100Go]

Update: i removed the dash panel to take a good look at the rod, and it was indeed disconnected. On both ends . As hard and much as i tried i could not access the place where the rod attaches to the flap mechanisms within the dash. The place the rod slides through is a 4 inch by 2 inch gap with no access to even reach the end of the rod. I can stir the rod through the whole access hole. I tried thought the drivers side pedal area( as someone suggested) and there is absolutely no access to the rod, the other side glove compartment area was the same access that I had from the front. I reattached it to the knob at least. I am wondering what can I try next? I have reassembled everything back. The weather is heating up a little more each day, and it's hard without cool air or even AC, heck -I don't even know if it works. A strange/surprising thing is all the blanks on the dash next to the hazard and ac switch have wired harnesses behind them -for what or leading to what- I have no idea? So any other ideas or suggestions on my detatched rod??? Thanks so far.