electrical gremlin

85 chevy K10. the problem 1 of 3.
1st. when i turn the blower motor on high the volt gauge will very low,low enough to dim the lights or disengage the compressor clutch. replaced the blower motor,problem still there,replaced the 65 amp alt with a 100 amp alt i had,problem still there,replaced the batt,problem still there. this only happens with the blower motor. you can turn everything else on and the volts hold at 13.turn the blower motor on and it drops.

2nd. motor will not heat up. 305 motor,2 core rad. when the temps get down into the 40* range, i can not get the motor to heat up over 120*. replaced the t-stat 2 times,still wont heat up. cover the rad up,eventually with enough time and driving it will get to 150*. leave the heater control valve closed it will heat up faster. why wont this motor get hot?

3rd. this just started. when the temp gauge raises off 100* it will start to go crazy,bouncing all over the place,temp sender bad?

High bypasses the ressitor bridge, it's switched to high setting, full 12V via the hi speed relay. There must be soemthing rong with the relay or the wiring.

Did you verify temps w/ IR gun???

3rd related to 2nd prob?

I will get a relay and give that a try.
I have not used an IR gun to check actual temp of cooling system, all i have to do is turn on the heater and fill the cold air that comes out. Take today,out side air temp was 42* this morning,drove for 15 minutes to get any heat. The colder it is,the longer it takes to get any heat,when it's below freezing,forget about it.

I'm going to ask what's probably a silly question.

Have you verified that your A/C isn't coming on as well when you turn on your heat? On the 85, defrost uses the A/C, but at times that control board will keep the A/C compressor on no matter the setting - which would serve to reduce your cabin temps.

I keep saying I'm going to paint mine, but love the get out of my looks of the truck now

easy check is to pull the green wired connector on the Compressor clutch. Also your air mix door might be stuck as well, check the connections on the ehater box under the glove box.

Pretty sure the compressor is not on, it's a 305 motor, the a.c. really drags it down. But I will disconnect the a.c. to make sure.

Time to do a serious flush of the cooling system. Pull the block plugs to see how bad it is.
Lots of bad tstats these days, may need to try more.
Heater cores plug very easily, if that's all you're judging by.

Start by making sure both ends of your battery and ground cables are clean. Don't have to look bad. They won't charge full amperage no matter what size the alternator.

Make damn sure the engine is nicely grounded to the body, a ~25 amp heater draw will accentuate an otherwise shaky ground and give all sorts of symptoms like what you have....

also need know what the alt voltage is when this happens, at the stud, not the battery or anywhere on the body....then to IF it is lo at the stud, need know what is going on at point L on the regulator, or the typical brown wire, it should be almost same as the stud output, passes through a light on the dash, or like our old sharks, maybe a resistance wire and no light....

:crutches:

I grabbed my IR gun on the way out the door this morning. Temp was 40*,drove for 20 minutes, temp gauge in dash read(when it was not jumping around) 120*, highest reading i could get with the IR gun was 115* and i took the reading in many different places under the hood. Pulled the rad cap off while still running and the cap was not hot to see if water was flowing,and no it was not. So what gives here. It's only gonna get colder out :cussing: Maybe it' time to get out in the garage and grab 1 of the motors laying around and build a bigger one :amazed:
So which one. 327,350,383,390,400,454 Ahhhh the choices.
I have to many motors in the garage.

kwplot34 said:

I grabbed my IR gun on the way out the door this morning. Temp was 40*,drove for 20 minutes, temp gauge in dash read(when it was not jumping around) 120*, highest reading i could get with the IR gun was 115* and i took the reading in many different places under the hood. Pulled the rad cap off while still running and the cap was not hot to see if water was flowing,and no it was not. So what gives here. It's only gonna get colder out :cussing: Maybe it' time to get out in the garage and grab 1 of the motors laying around and build a bigger one :amazed:
So which one. 327,350,383,390,400,454 Ahhhh the choices.
I have to many motors in the garage.

Click to expand...

Kinda lends a new twist to the old phrase...about wanting a 'HOT' engine....:nuts:

400s are for pickups :thumbs:

My diesel has similar problems of not getting warm enough, but not to the extent you've got. However, with mine once I put a load in it and it will get warm (push hard enough and it'll get too warm).... but I have a turbo, so it has help getting warm.

I presume you've put a piece of cardboard in front of the radiator with similar results?

What size radiator do you have? has someone replaced the original radiator with a heavy duty, or a diesel radiator?

Hmmm... where are you drawing fluid for your heater? If you're drawing at the pump and returning to the radiator, you'd be drawing the coldest water in - normally, that's not a real issue, but in your case, perhaps? If so, there's also a coolant pickup on the cross tube next to the return hose - replumb to that point.