AC Heater help needed.

Hi all,

I need some advice on the AC and heater issues I'm having. I've tried the search and cannot find anything like what I'm experiencing.

Here's what I know.

Start the car and let it get up to temp and I do the following:

The blower motor is working fine.
The re-circulation and fresh air switches work fine.
When I rotate the temperature switch from hot to cold I can here the solenoid for the AC compressor click into action.

However I cannot vary the temperature from hot to cold. It stays on 38 Deg C constantly coming out of the vents. So I'm assuming that the temperature control knob is working as I can hear the solenoid clicking on and off. So I am assuming its something to do with the unit behind the fuse box not physically shifting between the hot and cold. I do know if this is vacuum operated or electronically.

Any help would be much appreciated.

 

Do an advanced search on "hot water valve" in the Boxer/TR section -- when this system fails = the hot water valve defaults to the full open position. However, you need to determine if it's an electrical problem or a problem with the hot water valve itself. Those threads should give you some suggestions/checks to do...

 

Thanks Steve, I'll check over the connectors and then the hot water valve tomorrow.

 

Hi Steve, the connector has melted so looks like it's time to do the fuse box.

Do you or anyone know if the connectors come with the new boxes?

 

What are you saying?

Connector at FB or on water valve?

 

It's Melted at the fuse box. So I'm going to do a temp fix and see if it starts working again.

 

Certainly, the AC power connection in the k white connector at the TR fuse-relay panel needs to be healthy (and it's usually the first one to go since it has the highest current), but when that goes = everything AC won't work (no cabin fan operation, no AC compressor clutch operation, hot water valve never closes). Since you report that some of those functions do work, the k connector connection must still be sort of working - even if it looks a bit toasted.

Hope the repair solves the "always hot" problem (but I wouldn't be hopeful if the cabin fan was/is working before the repair). No, the white connectors/terminals in the wiring harness do not come with a new stock fuse-relay panel (RicambiAmerica might be source for those bits, but you're in the wrong hemisphere ) -- but getting everything stock and fresh is really not a long-term solution...

 

Hi Steve, I've sent an email to them about the connector and an email to the guys that make the upgraded fuse boxes. As you say it wasn't the source of the issue as its still the same. So I'll look under the passenger foot well and see what's going on with the hot water valve.

 

Just for some background -- was it working OK, and the problem started suddenly without changing anything else? Or did it start after replacing/working on the hot water hoses or some other work?

 

Hi Steve, It just started all of a sudden. Nothing was done on the AC or heating.

Was working fine the last time it was driven. Since then the gear oil has been done, door panels removed and cleaned up and front spoiler removed to be painted.

 

Ok I have checked the wiring to the hot water valve and it all works as it should.

So its leaving me thinking the following:

1, The hot water valve is defective and stuck partly open.
2, The temperature pot in the center console is defective and stuck on roughly 40 Deg C as thats all I seem to get. BUT when I turn this all the way to its coldest setting it does engage the mag clutch on the AC compressor.

Is there anything else I can check to test?

 

Although your result from #2 is a strong sign that #1 is the problem, doing the five resistance measurements at the unplugged AC ECU connector in the wiring harness as described on pages H29 and H30 of the TR WSM (and passing those) would be more evidence that #1 is the trouble and warrants more investigation. Of course, if you don't pass one (or more) of those resistance tests, that would take you in a different direction.

 

Hi Steve, I had a brief look for the ECU where it looks to be from the WSM but I couldnt see it. Is the AC ECU behind the fuse box? I'll give it a check tomorrow when I can and post the results.

 

Yes, it's mounted behind the fuse-relay panel.

 

Hi Steve,

Thank for all your help on this subject!

Checked all the resistances today and they are correct. I have approx 35 - 36 Deg C ambient when I checked it and they align with the figures shown on page H30.

So I'm guessing that means it can only now be the hot water valve.

Has anyone every tried to repair/free one and it work successfully since or is the general consensus just to swap it for a new one. If the latter is the only place to buy them Ferrari?

Craig

 

The internal sealing plunger is a replaceable unit (although the last time I bought one from a Mercedes Dealer, the parts guys remarked MB only had 4 left in the US -- and I took them down to 3). However, if the solenoid coil has failed then you are probably only left with getting a new one. This thread has some pics and other info (post #5):

http://www.ferrarichat.com/forum/mondial/419344-1987-mondial-heater-water-pump-switch-question-2.html

If you are lucky you might just have some debris on the seat preventing the plunger from sealing -- Good Hunting!

(adding the F PN 61079000 to this thread for future search)

 

Thanks again Steve thats perfect. I'll see if it will clean up tomorrow failing that I'll bung the supply side till I can either get the mono repair kit or a new one.

 

Hi all,

I still need advice on this one.

The valve is now replaced and I'm getting nice cold air. However I still cannot get heat. I've checked the readings again and all were fine except this time where the hot water valve is I no longer get 0v when the hot air is selected. The power is 12v when in the off position but its now reading 10v when the power is on keeping the valve closed.

Any ideas?

 

Air in the waterheater radiator ? Bleed it ...

 

Have you gone back and remeasured the resistance values at the unplugged AC ECU connector of all the sensors/controls as described on pages H29 and H30?

(I'm away from my TR wiring diagram, but I'll double-check this later, but I think: )

If those are still OK, one test you can do is with the AC ECU unplugged, key "on", measure the voltage at the hot water valve connector:

With AC "OFF" (or is it "STOP"?) button pressed = should read +12V

With any other AC button pressed = should read 0V (if this still reads +12V = that would be a sign that you have a relay problem. You haven't been mucking with and/or replacing the three relays on the AC unit itself have you?)

 

Hi Mel, I had just replaced my expansion tank and was bleeding the system when I found the problem. I had run the car up to temp and set the heater to max heat to open the vavle and get the water flowing.

My expansion tank looked as though it had a small pin hole but after taking it off and cleaning it up I found it was more like it had been shot with a shotgun lol.

 

Hi Steve,

Yes all the values were good as per the previous test. Ill check it with the ECU unplugged.

Ive not touched the relays but I did have a look to check they were all stock, which they are.

 

It´s tha damn bad Italian quality ...

Two ways you can go .... get yourself a used or new one OR have it derusted and coated on the inside.

For time being any reservoir will help you ... GM or BMW ...

Let us know how you did it by the end please.

 

Hi Mel, I've just had an alloy one made to the exact same shape and dimensions and coated in black paint for now. I want to get out and drive it as its been sitting for a couple of months while it was being worked on.

I'll replace it with a new one later. Mine was beyond repair. It looked fine except one small pin hole until it was cleaned up and we found it had rust everywhere. Each time we tried to clean it up it just started to fall apart .