1988 Carrera alternator light fickers with blower motors on

[tigerbillsbikes]

I just noticed that my alternator light flickers erratically, and seldom, when idling when the heater blower motor runs. The motor sometimes sounds like it is straining. Could this create a draw that would trigger the alternator light to come on?

[wwest]

Blower motors operating AND engine RPM sagging could well result in flashing/flickering alternator light. But worth checking/cleaning/burnishing battery posts/connections etc.

Which came first, the chicken or the egg.


Does the sagging RPM cause the voltage drop or does the voltage drop cause the sagging RPM...

[NathanR]

Many have had problems w. Blower motors. The rear blower grounds to the alternator ground post. I recently discovered a short between the power lead to the blower and that ground wire. And my blower fried itself last month.

The dash light feeds off of a little blue wire that is connected to to the alt., also. The voltage regulator could be suspect, too. I think if your voltage is dipping, the VR could the reason.

Sorry if I'm babbling, but all this stuff is connected and should be checked out. When I dug into mine, found the alt ground wire melted and the alt positive lead's insulation crumbling. See my recent posts for pics.

Suggestions: unplug the blower motor and check the resistance across both the motor and the plug. The motor windings should be ~5 ohms. The plug leads should be open resistance.

Also, get a voltmeter you plug into your cigarette lighter and observe voltage while in use. Try it with various electic accessories on and off. This should give you an indication if your VR is working correctly. Max voltage should be less than 14.5 and greater than 13(?, can't remember exactly)

Good luck
Nathan

[wwest]

If the blower motors are actually running they are unlikely to be the problem...if stalled, no back emf, their resistance is low enough to blow the appropriate fuses.

It is not at all unusual for the light to flicker on and off at lower engine RPM and a HEAVY current load on the 12 volt system.

[wwest]

Originally Posted by tigerbillsbikes

I just noticed that my alternator light flickers erratically, and seldom, when idling when the heater blower motor runs.

The motor sometimes sounds like it is straining.

How so, description please...

Could this create a draw that would trigger the alternator light to come on?

Engine "surging" dropping below normal idle and then recovery-overshoot?

[tigerbillsbikes]

Thanks for the replies. I noticed the light when I arrived at Daytona last Friday when it was cold.
The weather was nice later so I did not need the heat. I went to the Rolex race Saturday and Sunday (which was great) and I drove around a lot while down there.
I returned to Atlanta for work this afternoon with no problems and the car performed
otherwise flawlessly. I have owned this car for a little over a year and have done
a few things to it but I seem to only drive it occasionally therefore anytime anything seems even slightly unusual I become concerned. Oh well, the car and I get to know each other better I suppose.
I got a bit long-winded, but my plan when I finally get back home to the N.Ga. Mtns this weekend is to check everything visible, check the battery connections and voltage while running. The car does have a disconnect at the battery installed by the previous owner that could be loose (doubtful). I will most likely get the lighter voltage monitor as well.
I was really curious if there has been any history of known problems with the heating system on later Carreras.

[dshepp806]

Get that charging system on par, as well as voltage reg (along with real DC measurements).

Go from there. Typical failures of the blower manifest in overcurrent conditions that will blow the relative fuse.

Make sure the charging system and VR is healthy for the loads,..and battery maint (FIRST).

DS


DS

[awhnry]

Are you keeping the battery on a trickle charger? It is quite possible that the battery is low and pulling the whole system down. The fact that it worked on your long road trip to Daytona tells me that the system is working fine when there is plenty of current going thru the system. Modern computer cars wont even run if they dont see adequate current; ours will try. It is also possible that the VR and/or alternator are not up to the task. YMMV

[wwest]

Originally Posted by tigerbillsbikes

Thanks for the replies. I noticed the light when I arrived at Daytona last Friday when it was cold.
The weather was nice later so I did not need the heat. I went to the Rolex race Saturday and Sunday (which was great) and I drove around a lot while down there.
I returned to Atlanta for work this afternoon with no problems and the car performed
otherwise flawlessly. I have owned this car for a little over a year and have done
a few things to it but I seem to only drive it occasionally therefore anytime anything seems even slightly unusual I become concerned. Oh well, the car and I get to know each other better I suppose.
I got a bit long-winded, but my plan when I finally get back home to the N.Ga. Mtns this weekend is to check everything visible, check the battery connections and voltage while running. The car does have a disconnect at the battery installed by the previous owner that could be loose (doubtful). I will most likely get the lighter voltage monitor as well.
I was really curious if there has been any history of known problems with the heating system on later Carreras.

The rear blower in my '88 Carrera just up and quite recently. Traced the fault to a relay inside the heat controller module in the engine bay. Replaced, everything good, except for noticing that with a low battery but still crank/start the footwell blowers were still intermittent.

Turned out that the reason for that was due to the rear blower motor current flow detection circuitry, reed relay. Battery voltage would be low due to multiple crank/starts/troubleshooting, footwell blowers would not function until the battery supply voltage was brought back up, recharged, to a level to HARD drive the rear blower.

I didn't take note but I would bet the battery charge light would at least flicker during those low battery restart events.

[Chuck.H]

I get the feeling that even when new from the factory, our pre 90's cars could not keep up with the electrical power requirements of the heat and A/C blower fan requirements. Then you take into account the degrading of the Bosch fan motors over time and I think our systems struggle to keep up.

Reading on some other car forums, I see they often run an additional wire to the fuse block to better supply current to the fuses... anybody here try this?

Chuck.H
'89 TurboLookTarga, 372k miles

[wwest]

Owned 2 '78 Targa's, a '79 Targa, still own an '88 Carrera.

Over 100,000 miles on all of those, no indication of and lack of ability to keep the battery charged and/while supplying power to all electrical loads, as long as the system is up to factory standards.

[NathanR]

Originally Posted by tigerbillsbikes

I was really curious if there has been any history of known problems with the heating system on later Carreras.

Yes. Lots of issues w. Heating system esp. Blower motors, both rear and footwell. Tons of posts on both....

[tigerbillsbikes]

I need to add that I have yet to have any dead battery issues. It got really cold today in Atlanta with the snow and all. I ran the heat with the blowers on and did
not notice the alternator light flickering. Could simply be an erratic occurrence but I will continue to monitor the situation and check into it further.
Thanks again for all the feedback.