Wipers working on their own . . . excess heat

[david22401]

I purchased a 1973 450 SE (American model) a month ago and have a few newbie questions. First off, the car is beautiful. I love looking at it and love driving it. I found it on Craigslist for $200. There's some rust here and there and it needs new paint, but all in all it's pretty amazing. The car was rarely driven; part of a collection of a woman who's mother was a hoarder. I have 6 cars myself, so I'm not gonna go there.

There's a lot of heat coming from under the dash on my side. My son says he feels radiant heat on his side, but i can't speak to how much there is there. On my side it's pretty warm, definitely warm legs and feet. I've made sure the vents are in the off position so I'm assuming this is some sort of heat seepage from the engine compartment. The temp gauge is at 175, so the engine isn't overheating. Is this just a MB thing?

The wipers were fine for the first three weeks, but Thursday they started coming on on their own. At first it was just one random swipe. Then they would come on for three or four. Seem to go off when I stop and are triggered on again when I accelerate. Could be a voltage spike jumping on the motor when I accelerate or when i let off the brakes. I'm not sure where to look first. In the meantime I've pulled the fuse, but miss my horn . . . crazy drivers and all.

Anyway. Glad to be here. Love the car and this resource.

David

Fredericksburg VA USA (just south of Wash DC)

'63 Ford Falcon Futura
'65 Beetle
'71 Ford F100
'73 MB 450 SE
'84 Ford F150
'01 VW Westfalia Euorovan

[thysonsacclaim]

I'm not sure about your specific heat issue, but my car has a similar problem. The engine temp is generally not very high, but I feel heat on my legs. Mostly at higher speeds and when driven for a little while.

The first place I would check is just beneath the driver's seat, at the very front. Maybe lift the carpet slightly and then put your hand there when you're driving. This is where the heat is coming from on my car, and I believe someone in the forum reported that there is a vent there that pushes AC/Heated air into rear of the cabin.

It's also possible there is a rust hole somewhere that is letting radiant heat or exhaust fumes/heat into the car. I thought mine was exhaust fumes at first because it smelled awful inside, but now that the car is running better, I think this was just air coming in from the window (my AC isn't working at the moment, so I roll down the driver's window). It still warrants more inspection, just to be safe.

I don't know if the vent that goes under the seat is operated by a vacuum at some point or if it just stays open. If it stays open, a leak somewhere could be causing your problem.

Wish I could say more. It shouldn't be hard to fix, though.

[arman]

1.
The heating system of a W116 and maybe other Mercs or brands of that era is quite special. When you turn on the heating lever for the passenger side or driver side (the 'inner levers') the vacuum system opens a valve which allows cooling fluid to pass the heating element in the dash (which in a way is a 'second' radiator). It is a binary valve e.g. fully closed or fully opened. On both levers (driver's and passenger's side) are pneumatic microswitches that actuate this valve on the firewall in the engine bay.

To adjust heat to driver or passenger side individually these levers move the driver's or passenger's flap that blends outside air with warm air from the heaterbox. lever all the way up: hot air, lever low (but just enough up to have actuated the microswitch that opens the valve): slightly warm air.

The problem is - like I experience in my own w116 - that if there is something wrong with the flaps, the foam hinges of these flaps or bad adjusted flaps etc, etc, you get hot air anyway as soon as the valve is actuated. Because the flaps do not close properly and give to much air from the heater box.

Then you have the two other levers (the 'outer levers'), the right one regulates air for windshield and the left regulates air for the feet and passengers in the back, I think. If these flaps are maladjusted too, there is a change that you always get hot air down below no matter how you set the levers.

In my case the situation is as follows: the pneumatic microswitch on the driver side lever for heating is not working. Not so unexpected of course, because that one has been used most frequently. But what I didn't understand from the beginning was why I got warm air on both passenger side AND driver side, when I moved the passenger's side heater lever just up a little bit??!

The explanation is however simple: my hot air flaps are not working properly because of ageing (foam) hinge material or something else. That means that as soon as I push the passenger heater lever just a little upwards, the heater valve opens and hot coolant flows through the heater box. This is not passenger or drivers side specific! The flaps are taking care of that (when the car was new ). So I get hot air from both side vents and also from below if I want, but in my case the flaps for windscreen and foot well still work OK, so I can regulate where the hot air comes out, but I can not regulate the temperature too well because these temperature flaps will not close all the way anymore. And I cannot regulate passenger or driver side heat individually, again because these flaps won't close properly.

In your case it might be so that your heater levers are maladjusted/faulty and that your coolant valve is always open. It could also be vacuum related or maybe even a faulty valve which is 'stuck' open.
It could also be the levers or the flaps for windscreen or foot well regulation. But my guess is that your coolant valve is open all the time and the flaps are making the hot air flow to the foot well.

Try to shut down your central ventilator knob all the way (anti clock wise, the knob in the middle with ventilation modes I, II, III, defrost) and see if the problem still persists. I think you shut down the whole air flow that way (if it works properly, that is).

By the way the middle vents on the dash only give fresh air. At least in my case, because I don't have AC in my car. I'm not sure about AC equipped cars.

The solution to the flap hinges is documented here on the Forum, as I recall. The job isn't easy though, I haven't had the courage yet to start taking the whole ventilation intrails apart... But there are people who have done this successfully (MT?, WGB?) or are in the middle of such a project.

Just try to do a proper trouble shooting first to narrow down the problem, before you start ripping things apart.

2.
I don't know really about your wipers. Is it the interval mode that kicks in or the normal wiper mode? If the case is interval could it be that the air in the dash is so hot that it is actuating a bi-metall switch for the wiper interval? Just a wild guess, I guess.

It could also be that your heating/ventilation ducts aren't assembled properly by the PO? That means the hot air gets out from the wrong place and blows straight into the area under/behind the dash.

Good luck and keep us posted!

[thysonsacclaim]

Hmm... That gives me more to check out.

Only problem is the heater core is gone from my car and the outlet from the block goes right into the inlet part.

This was probably done to remedy a broken heater core.