Electrical issue - Non Mercedes - PeachParts Mercedes-Benz Forum

pj67coll · #1 12-08-2012, 10:31 PM

Wonder if anyone can provide insight into an odd electrical issue I experienced recently. I was riding in a 72 Cadillac like the one I used to own many years ago and it had some electrical problems. Short in the blower motor which kept blowing out the vents slightly even when climate control was turned off and the dash lights wouldn't come on but the one that perplexed me most was the indicators.

When I indicated either left or right I initially though the indicators were non-functional but it turned out that they did in fact work but only every twenty seconds or so. By which I mean that about every twenty seconds they would blink once and then nothing, the lights were steady for about twenty seconds then another blink etc. (I was driving at night so the lights were on). So basically for whatever reason the indicators were just unbelievably slow.

Any idea what can cause that? Ive seen indicators on either side flashing hyper-speed if a bulb is out on a that side but I've never seen them work at a snails pace before.

- Peter.

Benz Fan · #2 12-08-2012, 10:59 PM

Have you ever replaced the flasher relay?

pj67coll · #3 12-09-2012, 11:08 AM

Quote:

Originally Posted by Benz Fan

Have you ever replaced the flasher relay?

No my car so no. But would that likely be the culprit? I guess it could be but I'm not an electrician so curious.

- Peter.

Brian Carlton · #4 12-09-2012, 11:21 AM

Quote:

Originally Posted by pj67coll

No my car so no. But would that likely be the culprit? I guess it could be but I'm not an electrician so curious.

- Peter.

That's the most likely culprit, provided the voltage was up.

I recently had the turn signals on the 300SD begin to slow and sound like they might fail to flash. Replaced $30. relay and all is back to normal.

spdrun · #5 12-09-2012, 11:28 AM

Speaking to the blower motor, a lot of older American cars had blowers that couldn't be turned off 100%. This was by design to prevent exhaust buildup in the interior.

KarTek · #6 12-09-2012, 11:41 AM

Older cars (and a few newer ones) use a load based flasher. You can buy a solid state replacement that will flash at the same rate regardless of the load.

cmbdiesel · #7 12-09-2012, 01:47 PM

Quote:

Originally Posted by spdrun

Speaking to the blower motor, a lot of older American cars had blowers that couldn't be turned off 100%. This was by design to prevent exhaust buildup in the interior.

Every older GM I have owned was that way.

pj67coll · #8 12-09-2012, 03:07 PM

Quote:

Originally Posted by cmbdiesel

Every older GM I have owned was that way.

Interesting. So that means that if the key in the ignition but switched off and the climate control fan is in the off position and there still is a very faint breeze coming out of the air vents this is correct?

- Peter.

kerry · #9 12-09-2012, 03:40 PM

GM started doing that with the blowers around 69 or 70. I find it irritating. I've owned a couple and tapped a switch into the blower circuit to stop it. I thought it would wear out the blower motor much more quickly. Also, it could be that someone towed a trailer with the car and put in a heavy duty flasher to slow down the rate with lots of lights in the circuit.

cmbdiesel · #10 12-09-2012, 05:22 PM

Quote:

Originally Posted by pj67coll

Interesting. So that means that if the key in the ignition but switched off and the climate control fan is in the off position and there still is a very faint breeze coming out of the air vents this is correct?

- Peter.

Fan should only come on with ignition on. Off and everything should be off.

pj67coll · #11 12-09-2012, 05:33 PM

Quote:

Originally Posted by kerry

GM started doing that with the blowers around 69 or 70. I find it irritating. I've owned a couple and tapped a switch into the blower circuit to stop it. I thought it would wear out the blower motor much more quickly. Also, it could be that someone towed a trailer with the car and put in a heavy duty flasher to slow down the rate with lots of lights in the circuit.

Definitely no towing with this car. That much I do know.

- Peter.

pj67coll · #12 12-09-2012, 05:37 PM

Quote:

Originally Posted by cmbdiesel

Fan should only come on with ignition on. Off and everything should be off.

That's what I figured. But to be honest I'm now not certain that the ignition was actually off. I might have had it in the first detent while this was going on.

- Peter.

Benz Fan · #13 12-09-2012, 05:44 PM

Quote:

Originally Posted by pj67coll

Interesting. So that means that if the key in the ignition but switched off and the climate control fan is in the off position and there still is a very faint breeze coming out of the air vents this is correct?

- Peter.

No. If the ignition switch is in the "off" position, the blower should be 100% off. I wonder if the ignition switch may be at fault. Can any other electrical components that would normally be inoperable with the ignition switch off be operated?

pj67coll · #14 12-09-2012, 07:51 PM

Quote:

Originally Posted by Benz Fan

No. If the ignition switch is in the "off" position, the blower should be 100% off. I wonder if the ignition switch may be at fault. Can any other electrical components that would normally be inoperable with the ignition switch off be operated?

Unfortunately I don't know which components on this car that would relate to. It's been 16 years since I owned one and the test was rather hurried.

- Peter.